Hindawi
Advances in Materials Science and Engineering
Volume 2022, Article ID 4249657, 12 pages
https://doi.org/10.1155/2022/4249657
Research Article
Organic Photoelectric Materials and Organic Photoelectric
Devices Based on Smart Image Sensors
Gang Huang
Science and Technology Department, Chongqing Vocational College of Transportation, Chongqing 402247, China
Correspondence should be addressed to Gang Huang; huanggang@cqjy.edu.cn
Received 17 May 2022; Revised 21 June 2022; Accepted 29 June 2022; Published 21 July 2022
Academic Editor: Haichang Zhang
Copyright © 2022 Gang Huang. This is an open access article distributed under the Creative Commons Attribution License, which
permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
With the development of the times in recent years, people’s requirements for vision are no longer limited to the original
foundation. As the core of research in this field, organic electroluminescence has paid great attention to the research points in the
application of organic optoelectronic materials and devices in the world. From the relevant scientific research results in recent
years, for example, organic light-emitting diodes can be used in flat-panel displays and solid-state lighting, organic photovoltaic
cells can be used as a clean and renewable energy source to effectively alleviate the current energy needs of society, and organic
storage, sensors, and so on show great promise for application. It can be seen that the research of organic optoelectronic materials
and their devices will be the core hot spot of future new energy research. In the past, traditional organic optoelectronic materials
are updated through the regulation strategy of covalent modification of the molecular structure. In recent years, new effective
methods have been obtained to regulate the properties of excited states through physical stimulation (such as mechanical force,
temperature, electric field, and magnetic field). The type of research experiment in this paper is based on the current hot smart
image sensor, with the addition of organic complexes of mononuclear metal platinum and iridium metal and the organic
optoelectronic device in the form of host and guest doping. The experimental results show that using PVK without energy transfer,
polyvinyl carbazole (PVK) had been widely used as blue luminescent material and hole transport layer in electroluminescent
device research. Simple mononuclear platinum and iridium metal complexes cannot obtain white light. For OPV devices, by
selecting the correct solvent to control the bulk heterojunction, it exhibits better photovoltaic performance. Solvents play an
important role in phase separation. In organic solar cells (OPV) consisting of an electron donor (D) and an acceptor (A),
optimizing the D-A interface produces efficient charge separation, effectively separating excitons at the D-A interface and forming
continuous electron and hole transport channels, and effective charge transport between electrodes plays a positive role.
1. Introduction
1.1. Background. Under the current conditions of rapid
economic and social development, the application prospects
of organic optoelectronic materials are very attractive. Because there are effective solutions to the problems of luminous brightness, efficiency, and lifespan at present, that is,
through the application of light-emitting diodes, electrical
energy can be efficiently converted into light energy, which
has a wide range of uses in modern society, such as lighting,
flat-panel displays, and medical devices. It will be widely
used in civil and military in the future. First of all, highefficiency white light can be used in the field of lighting.
Various forms of lamps and lanterns bring new visual
impact. Colorful lights can be used in stage lighting design;
at the same time, they can also be used to make large-screen
full-color high-definition flat-panel displays. It can also be
used to make e-books. The textbooks will no longer be heavy
and thick paper books, but thin and light e-books. The soft
light source will make reading more colorful. In the military,
it can be used for display instrument panels of operating
platforms such as tanks and airplanes. Compared with organic optoelectronic materials, which have the characteristics of low preparation cost, small workload during
processing, and convenient operation, organic optoelectronic devices have low cost, lightweight, easy design, and
synthesis of materials and can be made into large-area
displays, flexible, and foldable displays [1]. The screen,
2
because of its simple preparation process, etc., can attract
more attention from all aspects. In recent years, optoelectronic devices have been developed with their different
functions. What is beneficial to modern life is electronic
equipment that can be used to retrieve images and smart
cards, as well as memory cards and sensors with excellent
applications [2]. In the case of organic optoelectronic devices, the interface has a significant impact on the performance and service life of the device. Image sensors use the
photoelectric conversion function of photoelectric devices. It
converts the light image on the light-sensitive surface into an
electrical signal with a corresponding proportional relationship with the light image. Image sensors are widely used
in digital cameras and other imaging devices. Light-emitting
diode is a common light-emitting device, in the field of
electronic display, and is one of the commonly used materials, the study of which can well enhance the efficacy of the
response and provide a wider viewing angle.
1.2. Significance. In recent years, research on organic
electroluminescent devices and photovoltaic equipment and
accessories has continued. Related scientific research results
are still emerging. It is believed that in the next few years,
organic electroluminescent devices will move from the
laboratory to the market, and photovoltaic equipment and
organic equipment will also be improved. Related research
content has developed an organic photovoltaic device with
an efficiency of 8.22%. The efficiency of organic solar cells
exceeds 15%, which will be the next goal. For some time to
come, organic optoelectronic materials and devices will still
be the focus of new energy research.
1.3. Related Work. For related research, many scholars have
laid the foundation for this empirical research. In sensor
research, Hasani A investigated the latest developments in
the application of two-dimensional materials and MOF in
taste sensing applications. From the review, they concluded
that these materials will become promising candidates for
taste applications, leading to the development of the food
industry [3]. Xia et al. demonstrated the most comprehensive performance and performance of organic ferroelectric polymer materials and their composites, as well as
the improvement of organic-inorganic hybrid ferroelectric
materials. Finally, the future growth rate of ferroelectric
materials is predicted to some extent [4]. In the use of
wireless sensor networks (WSNs) to achieve accurate perception of agricultural planting information, Fen et al.
proposed a hybrid WSN node based on smartphones. Nodes
can support traditional central agricultural management
functions through terminal/host configuration. Tourists and
farmers can also directly visit the node and use on-site
information services. The design of the node hardware and
the corresponding smartphone application program is
discussed, and the test results in the BTH Tourism Farm are
given [5]. Based on sensor research and innovation, Andika
et al. demonstrated a new nanoporous structure of aluminum 1,8,15,22-tetra29H, 31H chlorinated phthalocyanine
(AlPcCl), which is prepared by a template-assisted method
Advances in Materials Science and Engineering
for humidity sensor. The nanoporous sensing layer was
prepared by wetting the anodic aluminum oxide template
with a solution. AlPcCl solutions of different concentrations
are spin cast on the template at different speeds. Both capacitance and resistance responses are measured as a
function of different relative humidity levels. The sensor
shows a wide operating relative humidity range and responds at a relatively low humidity level. The morphological
changes were studied by field emission scanning electron
microscopy. The sensor shows a wide operating relative
humidity range. The sensor shows better performance
through improved sensing parameters, highlighting the
unique advantages of low-molecular nanostructured sensing
layers for humidity sensors [6]. Choi et al. proposed a pixel
aperture technology in complementary metal oxide semiconductor (CMOS) image sensors for 3D imaging. In traditional camera systems, the aperture is located between the
object and the CMOS image sensor (CIS); this type of image
sensor consists of an array of pixels with red, green, and blue
(RGB) Bayer pattern color filters [7]. Liu et al. introduced the
evaluation of the optical and electrical characteristics of
ultrathin body and buried oxide (UTBB) MOSFETs with
different structures. UTBB MOSFET can realize photoelectric conversion by integrating a doped well or photodiode under the BOX. For lightly doped wells, well-UTBB
(W-UTBB) image sensors are more sensitive to light. On the
other hand, the photodiode-UTBB (PD-UTBB) image
sensor has a larger full well capacity. The effects of good
doping concentration and interface traps at the BOX/well on
the optoelectronic properties of the two devices have been
studied. A good doping concentration has a great influence
on the photosensitivity of W-UTBB. Interface traps will
increase the dark current of W-UTBB and reduce the internal quantum efficiency (IQE) of PD-UTBB [8]. In the
research on organic optoelectronic materials, Yoon’s multipattern nanostructures prepared by synergistically combining block copolymer lithography and nanoimprint lithography have been used as back reflectors to enhance light
absorption in organic optoelectronic devices. Due to efficient
light scattering and plasma effects, multi-patterned electrodes significantly improve the performance of organic
photovoltaics and phototransistors and expand their practical application range. The abovementioned scholars all
need an over-professional and in-depth knowledge base for
related research, the operation process is complicated, and
there is a certain degree of danger.
1.4. Innovation. This research mainly carried out optimization and performance research on two aspects of doped
organic electroluminescent white light devices and organic
photovoltaic devices. (1) In the experiment, the mononuclear iridium (platinum) ring metal complex with nonplanar
structure was mainly studied systematically [9], and the
doped electroporation was designed with PVK as the main
body and platinum and iridium metal complexes as the guest
material, and studied the optoelectronic properties of this
series of OLEDs. (2) The organic photovoltaic device is
mainly based on the PC61BM acceptor and P3HT [10]. In
Advances in Materials Science and Engineering
this paper, three materials, P3HT (polymer of 3-hexylthiophene), PFO-ThPz-Tpa copolymer, and PFO-FCz-DBT30
copolymer, are proposed as guest materials to prepare solar
cells, and they are optimized in the preparation process to
further investigate the performance of photovoltaic devices
[11].
2. Organic Photoelectric Materials Based on
Smart Image Sensors
2.1. The Development Status of Organic Optoelectronic
Materials. In 1963, American scholars first discovered the
luminescence phenomenon of organic materials [12]: under
400 V DC voltage, single-crystal anthracene will emit weak
fluorescence. Although the turn-on voltage and efficiency were
not good at that time, the discovery made humans realize for
the first time that organic materials can also emit light, laying
the foundation for future research on organic electroluminescence. Until 1987, it was reported that 8-hydroxyquinoline
aluminum (Alq3) [13], an organic small molecule lightemitting material, was prepared by vacuum evaporation
method to prepare a sandwich structure of green fluorescent
OLED (organic electroluminescent display) devices [14]. This is
also the world’s first OLED device, device structure, and
molecule. The structure is shown in Figure 1. The turn-on
voltage of the device is less than 10 V, and the brightness is
more than 1000 cd/m2. This research result has attracted
worldwide attention as soon as it was reported. People began to
pay attention to the potential applications of organic materials
in the display field [15, 16]. Organic optoelectronic materials
are mainly used in organic solar cells, organic light-emitting
diodes, and OLEDs and other displays. Due to the rapid development of the electronic industry, many photoelectric
display panel companies need organic optoelectronic materials.
Research has gradually stepped onto the stage.
After years of development, some unique advantages of
OLED [17] have been gradually discovered by mankind: no
backlight, ultra-fast response speed, wide viewing angle, wide
color gamut, flexible and bendable, etc. [18]. Compared with
traditional liquid crystal display technology, OLED can better
meet human visual requirements [19]. In addition, OLED is
also simpler and lower in manufacturing cost than LCD
(liquid crystal display) in terms of process, so OLED is also
known as the third-generation display technology after LCD.
At present, OLED has been commercialized in large-size
display screens, small- and medium-size mobile phone
screens, car display screens, etc., and has formed a rivalry with
LCDs in the market, and the prospects are promising [20].
2.2. Working Principle Based on Smart Image Sensor.
Image sensors are widely used in imaging devices such as
digital cameras. Image sensors in the past used analog signals
[21, 22]. The rapid development and progress of image
sensors have made it possible to be used in space detection.
According to different photodetectors used, image sensors
can be divided into grating type and photodiode type [23].
Because organic light-emitting diodes are relatively lighter,
thinner, and more flexible, the production process is easier.
3
N
Mg/AI
Alq3
O
O
Diamine
ItO Glass
AI
N
N
O
Figure 1: Fluorescent OLED and luminescent material Alq3
prepared by Deng Qingyun and others.
Therefore, it is analyzed in this paper. Analyzing the photodiode, it is found that when the electric field strength in the
space charge region becomes larger, it is more likely to
produce drift motion; i.e., the minority carriers in the P and
N regions will make directional motion. The depletion region will remain stable when the diffusive motion and drift
motion reach equilibrium; it is found that when the diffusion
motion and drift motion reach equilibrium, the depletion
region will remain stable [24], as shown in Figure 2. At this
point, the PN junction is in thermal equilibrium. According
to the theory of semiconductor physics, the height of the
space charge region, which is the barrier region, is QV0, and
the width of the depletion region, W, and the PN junction
capacitance, Dc, are expressed as follows:
N0N1
QV0 � Kt ln 􏼨
􏼩.
N21
(1)
The QV0 in the formula represents the height of the
barrier, and its content shows that it is related to the doping
concentration.
􏽳������������������
2δ(V0 − V) N1 + N0
W�
.
(2)
q
N21
Formula (2) shows that the V voltage can affect the width
of the junction region, and it also shows that W will become
larger if it is a forward bias [25].
Considering the sudden change in capacitance based on
junction energy:
􏽳����������������������
Qδ
N1N0
1
(3)
Dc � a
·
·
.
2 (N1 + N0) (V0 − V)
It can be seen from (3) that the capacitance Dc is related
to the voltage. The specific performance is Dc when forward
bias will become larger; otherwise, it will be reduced.
In the above formula, K � 1.38 × 10− 23 J•k; t represents
temperature. A represents the cross-sectional area of
junction energy; δ is the electrical constant of the semiconductor. A voltage is applied to the PN junction under the
condition of thermal equilibrium:
Ld � L0BQv/kt − L0.
(4)
L0fQV/kt expresses the forward current flowing from the
P area to the N area. When V � 0, it is in a balanced state. L0
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Advances in Materials Science and Engineering
P
N
W
qV0
Figure 2: PN combination at zero offset position.
represents that the reverse charge saturation current will
grow with the increase in temperature. Therefore, current
will be generated by the reverse bias voltage.
If a negative resistance is added at this time, Hrs represents that the junction resistance of PN can be ignored. So,
the resistance of the load HL can be expressed as follows:
Ll � Ld − Lg � L0BQv/kt − L0 − Lg.
(5)
When the photocurrent Lg is proportional to the intensity of the incident light,
Lg � Es · S.
(6)
The sensitivity of the ES meter in the formula is as
follows:
Ll � Ld − Lg � L0BQv/kt − L0 − Es · S.
(7)
When there is no load, in the formula Ll � 0, the opencircuit voltage at this time is expressed as follows:
Vmn �
kt
Lg
In􏼚1 + 􏼛.
Q
L0
(8)
In Lg ≫ L0, it is generally expressed as follows:
Vmn ≈
kt
Lg
kt
Es · S
In􏼔 􏼕 ≈ In􏼢
􏼣.
Q
L0
Q
L0
(9)
HL � 0, when short circuit is expressed as follows:
LEm � Lg � Es · S.
(10)
At this time, the short-circuit current is directly proportional to the intensity of the incident light, and a reverse
bias voltage is usually applied to the PN junction. Since the
reverse bias voltage is consistent with the direction of the
electric field in the junction, the space charge region will
become wider and the barrier height will change. When QV0
increases to Q(V1 + Vr), the electric field strength in the
space charge region becomes larger, and the photo-generated
electron-hole pairs are more likely to drift, so the frequency
response characteristics of the device can be improved [26].
2.3. Principles of Organic Optoelectronic Devices. Principle of
Organic Light-Emitting Diode [27]: the structure of an
organic light-emitting diode is shown in Figure 3. It is
composed of a high-performance transparent indium tin
oxide (ITO) anode, a light transmission layer, an electrical
transmission layer, an organic light-emitting layer, and a
working metal cathode [28].
The energy level arrangement of the organic material
device is shown in Figure 4. If a forward electric field is
applied, under its influence, holes are injected into the
transport layer through the ITO anode with high efficiency,
and electrons are injected into the electron transport process
through the metal cathode at low power. The electron pair is
formed by the recombination of electrons, and the holes are
fixed by decomposition, electroplating, quenching, and
other methods and easily return from the excited state to the
ground state [29].
Principle of Organic Photovoltaic Cells [30]: organic
photovoltaic cells are usually composed of a transparent
indium tin oxide (ITO) anode, an organic process, and a
metal cathode [31]. The model is shown in Figure 5.
Figure 6 illustrates the principle of organic photovoltaic
cells. When sunlight passes through the ITO electrode and
reaches the organic active layer, the organic material in the
active layer absorbs the energy of incident photons to form
photo-generated electron pairs. Molecular van der Waals
forces work together [32], and the excitation of electrons and
incident photons restrain the occurrence of electron pairs
[33]. Under the potential of the receptor interaction, the
electron pair is separated into electrons and holes, and the
electrons jump into the LUMO energy phase of the acceptor
and transition to the HOMO energy phase of the free
substance [34].
3. Experimental Research on Organic
Optoelectronic Devices Based on MetalOrganic Complexes
In this study, the phosphorescent material platinum-iridium
metal-organic complex was doped into the host material,
and the organic layer was completed by the suction sheet
spin coating process, and the annealing temperature was
120°C. PVK has a strong hole transport ability. The electron
transport material PBD(2-(4-biphenyl)-5-phenyl) is added
to balance the injection of carriers, and the ratio of PVK to
PBD is 7 : 3. The device structure is ITO/PEDOT:PSS
(40 nm)/PVK-PBD:sample
(75 nm)/LiF
(0.5 nm)/Al
(100 nm). In the experiment, the solvent is chlorobenzene
(CB), and the mass ratio of the guest material to the PVKPBD (wt%, 7 : 3) blend is 0.5%, 1%, 2%, 4%, and 8%.
3.1. OLEDs/OPV Device Manufacturing Process 1.
Generally speaking, the preparation process of OLEDs/OPV
devices includes the processing of ITO glass substrate, the
preparation of organic functional layers, the preparation of
cathode modified layers and metal cathodes, and the
packaging and testing of devices. The following is a detailed
introduction to the specific steps:
Advances in Materials Science and Engineering
5
LUMO
Metal cathode
ET electron
transport layer
3
Organic emitter
HIT cave
injection layer
1
anode
4
2
Glass base
5
5
Light output
4
Figure 3: Organic light-emitting diode structure.
ITO
2
LUMO
1
4
3
3
HOMO
donor
acceotor
metal
Figure 6: Sorting of organic photovoltaic cells.
HOMO
2
1
ITO
HTL
ETL
metal
Figure 4: Energy level ranking of organic light-emitting diodes.
metal
Active layer
TCO
glass
Figure 5: Organic photovoltaic cell structure.
(1) The ITO glass resistance used in the ITO glass
substrate processing experiment is 15 Ω. First, a glass
knife is used to scratch a 15 × 60 mm2 glass substrate,
and a layer of vacuum tape is stuck on the side where
the ITO is deposited to ensure the tape. The edges are
neat and there are no air bubbles, especially the edge
part; otherwise, it will be corroded. A utility knife is
used to scratch the 3 mm × 80 mm tape, the protruding part of the tape is stuck on the back to
prevent the ITO at the edge from being corroded,
then the ITO glass substrate is attached face-up, a
layer of zinc powder in a Petri dish is spread and
corroded with concentrated hydrochloric acid for
25∼30 s, the residue attached to the surface is quickly
rinsed with a large amount of water, and finally the
tape is removed; the substrate with neat edges is
selected, and glass is used. The knife is divided into
three equal sections and marked on the back for later
use.
(2) Preparation of Organic Functional Layer at Present:
there are two main methods for making OLED/OPV
organic functional layer: small molecule materials
generally use vacuum thermal evaporation; polymer
materials use wet spin coating technology.
(1) Vacuum Thermal Evaporation: 20 small molecule thermal evaporation process is usually
suitable to ensure that the vacuum degree is
∼10–4 Pa. The remaining gas after the vacuum
may have a greater impact on the performance of
the device.
(2) Wet Spin Coating Process: the wet spin coating
process is mainly divided into the following
categories: (a) suction sheet spin coating polymers are usually cross-linked, easily decomposed
by heat, and are not easy to evaporate and deposit
in the vacuum evaporation chamber. Therefore,
in general, it is dissolved in a suitable solvent and
deposited on the substrate through a suction
sheet spin coating process. However, this limits
the properties of the polymer to be soluble; the
same solvent can no longer dissolve other
polymers; otherwise, the solvent corrosion effect
will appear. The production of flexible devices
can be based on the principle of similar compatibility between solvents, using different solvents to dissolve different polymers and orderly
spin coating to form a film. Although the
thickness of the film produced by the spin
coating process can be adjusted by controlling
the concentration of the polymer in the solution,
6
Advances in Materials Science and Engineering
the spin coating rate, the spin coating temperature, etc., however, it is difficult to produce a
film with a certain thickness and control the film
thickness by monitoring the deposition process.
In the semiconductor display industry, the spin
coating process has been applied. However, the
production of large-area flat-panel displays
cannot be completed smoothly with the spin
coating process. (b) Doctor blade process: in this
process, the polymer is dissolved in a solvent and
then coated on the substrate to form a certain
thickness of film thickness, and the excess part is
removed by precise doctor blade technology.
Compared with the spin coating process, it is
easier to make a relatively thick film, but the
thickness of the film must not be less than
100 nm. This process is more common in the
production of OLEDs. (c) Wet injection molding
method: Yang et al. used inkjet printing technology to make OLEDs, which is a major advancement in the wet film manufacturing
process. Compared with the wet sucking sheet
spin coating process, wet injection molding
technology can be used to make double-layer
PLEDs, that is, adding organic layers that are not
compatible with each other.
3.2. Characterization of Physical and Chemical Properties of
Materials Made of Light-Emitting Devices Based on Mononuclear Platinum and Iridium Complexes. The thermal
stability of mononuclear platinum and iridium metal-organic complexes P1 and P2 are calibrated, as shown in
Figure 7. Under the protection of nitrogen, the thermal
weight loss of the two mononuclear complexes was measured at a temperature program rate of 20°C/min. The two
complexes P1 and P2 have good thermal stability, and the
temperature (Td) at 5% mass loss is 307°C and 292°C,
respectively.
The UV-visible absorption spectra of the two mononuclear metal complexes P1 and P2 in CH2Cl2 (10–5 M) are
shown in Figure 8, and the relevant parameters are shown in
Table 3.1. P1 exhibits three absorption peaks with different
intensities near 240, 335, and 353 nm. P2 exhibits two weak
absorption peaks with different intensities in the 260 nm and
350–450 nm regions. Among them, 240 nm and 260 nm are
the π − π ∗ transition absorption of platinum-iridium
mononuclear metal, the absorption peak at 350∼450 nm is
the transition absorption from the metal to the ligand, and
the absorption of P1 at 330 nm and 350 nm the peak is
attributed to the transition absorption of MLCT.
Figure 9 shows that in CH2Cl2, the complexes P1 and P2
have strong emission peaks near 475 nm and 497 nm. The
emission peak around 475 nm can be attributed to the
1MLCT transition emission, and the emission around
497 nm can be attributed to the 3MLCT transition emission.
At the same time, we studied the electrochemical properties
of the two materials. The HOMO and LUMO energy levels of
the material are obtained by the following empirical formula:
HLUMO � − (Hred + 4.38)(Ev),
HLUMO � − (H0x + 4.38)(Ev),
(11)
Hg � − (HLUMO + HHOMO)(Ev).
The LUMO and HOMO energy levels of P1 are
ELUMO � 3.46Ev and ELUMO � 6.63Ev, respectively; the
LUMO and HOMO energy levels of P2 are ELUMO � 3.2Ev
and ELUMO � 5.62Ev, respectively.
3.3. Characterization of Electroluminescence Performance of
Light-Emitting Devices Based on Mononuclear Platinum and
Iridium Complexes. The electroluminescence spectrum of
the mononuclear platinum complex P1 device at a voltage of
8 V is shown in Figure 10. The electroluminescence emission
peak of PVK + PBD undoped metal complex device is shown
in Figure 10.
It can be seen from Figure 10that when the doping ratio
is 1%, the EL spectrum presents three peaks: 450nm, 500nm,
and 650nm. The peak at 431 nm is attributed to the emission
peak of PVK. Starting from the doping concentration of 2%,
as the doping ratio increases, the luminescence intensity of
PVK at 431 nm gradually decreases, indicating that the
concentration increases and the energy transfer efficiency
between PVK and P2 gradually increases, which inhibits the
luminescence of PVK. At the same time, the increase in the
doping concentration also increases the proportion of the
metal complexes directly capturing the carrier emission, and
the increase in the concentration also causes the complexes
to produce exciplex emission, which changes the spectrum.
When P1: (PVK + PBD) doping concentration is 0.5%, the
spectra under different driving voltages are shown in Figure 11.
With the increase in the voltage, there is basically no change in
the position of the emission peak at 431 nm, but when the
voltage is increased to 12 V, the emission intensity of PVK
decreases and the excimer emission between the complexes
increases. It shows that this luminescence should be related to
the environment in which the excited state P1 molecule is
located. This is consistent with the phenomenon described in
articles reported in the literature. As the voltage increases, the
number of carriers increases, the number of potential wells
formed by the guest material increases, the number of carriers
directly trapped increases, and the luminescence intensity
increases, making the luminescence of PVK relatively weak.
The EL spectrum under different voltages is shown in
Figure 11. The comparison of experimental results shows
that when the doping ratio is 1%, the EL spectrum shows
three peaks: 431 nm, 476 nm, and 530 nm. The emission peak
of P2 has many similarities with P1. The emission peak of
PVK is at 431 nm, the emission peak of P2 itself is at 476 nm,
and the emission peak at 530 nm is derived from the
emission of the excimer between P2 molecules (excimer
emission). Starting from the doping concentration of 2%, as
the doping ratio increases, the luminescence intensity of
PVK at 431 nm gradually decreases, indicating that the
concentration increases and the energy transfer efficiency
between PVK and P2 gradually increases, which inhibits the
luminescence of PVK. At the same time, it can be seen that
Advances in Materials Science and Engineering
7
N
N
P
T
F
O
O
P
T
F
N
O
O
N
F
F
O
(CH2)6
O
O
(CH2)6
O
Figure 7: Molecular structures of P1 and P2 complexes.
1.2
1.2
1
0.8
Normalized PL intensity
Nomrnalized UA
1
0.6
0.4
0.2
0.8
0.6
0.4
0
0
100
200
300
400
Wavelenth
500
600
P1
P2
0.2
0
0
450
Figure 8: UV-visible light absorption spectrum of metal complexes
P1 and P2.
the emission intensity at 476 nm of P2 gradually decreases,
and the emission intensity at 530 nm gradually increases.
The decrease in emission intensity at 476 nm may be due to
the absorption effect of the complex itself. The increase in
luminescence intensity at 530 nm may be due to the increase
in doping ratio, and there is interaction between molecules,
the probability of transition between molecules increases,
and the formation of excimer luminescence.
Although the ignition voltage of platinum and iridium
mononuclear complexes is relatively low, which is basically
between 7 V and 9 V, the white light region luminescence
spectrum is obtained, but pure white light is not obtained.
4. Optimization and Performance Research
Analysis of Organic Photovoltaic Devices
4.1. The Influence of Different Solvents on the Performance of
Polymer Devices. The experimental donor material is the
copolymer PFO-3-ThPz-Tpa, and the molecular formula is
shown in Figure 12. The acceptor material is PC61BM, and
500
550
600
650
Wavelenth
P1
P2
Figure 9: PL spectrum of metal complexes P1 and P2 in CH2CI2.
chlorobenzene (CB) and dichlorobenzene (DCB) are used as
solvents.
Due to the difference in the solubility of polymers in
different solvents, the morphology of the prepared photosensitive film is different, and the morphology of the photosensitive layer will have a great influence on the photovoltaic
characteristics of the device. The polymer PFO-3-ThPz-Tpa has
good solubility in aromatic solvents chlorobenzene and dichlorobenzene, and PCBM has good solubility in these two
solvents. Therefore, we choose two solvents, chlorobenzene
and dichlorobenzene, to make two different photosensitive
layers, and the AFM morphology is shown in Figure 13.
The photovoltaic performance of the device is tested
under 100 mW/cm2 intensity of light. The photovoltaic
performance parameters when DCB is used as a solvent are
η � 1.87%, Jsc � 7.83 mA/cm2, Voc � 0.67 V, and FF � 36%;
when CB is used as solvent, the photovoltaic performance
8
Advances in Materials Science and Engineering
1.2
Normalized intensity
1
R
N
R
n
R=n-octfl
0.8
N
0.6
N
0.4
OR
0.2
OR
Figure 12: Copolymer PFO-3-ThPz-Tpa structure formula.
0
400
450
500
550
600
650
700
Wavelength
1%
2%
4%
8%
Figure 10: EL spectrum of metal complexes.
0.0012
0.001
Normalized intensity
N
0.0008
0.0006
0.0004
0.0002
0
400
500
600
700
Wavelength
11 V
9V
8V
7V
Figure 11: 1EL spectrum under different voltages.
parameters are η � 2.09%, Jsc � 7.51 mA/cm2, Voc � 0.76 V,
and FF � 37%. These differences in photovoltaic performance are due to the different solubility of donor and acceptor materials in different solvents and different solvent
volatility, which will have a greater impact on the morphology and phase separation of the film. A suitable solvent
can make the two phases fully miscible, to increase the
contact area of the donor and acceptor heterojunction
phases and form a good interpenetrating network structure,
which is conducive to the separation of excitons and the
transport of electrons and holes. The recombination of
photo-generated carriers is reduced.
4.2. The Performance of Polymer Devices with Different Ratios
of Donors and Acceptors. In the experiment, we used P3HT
as the donor material and PC61BM as the acceptor to study
the effect of blends in different proportions on the morphology of the photosensitive layer. The results are shown in
Table 1.
With the increase in the proportion of PCBM, P3HT is
gradually covered by PCBM. With the further increase in
PCBM mass fraction, PCBM micro-islands in the bulk
heterojunction gradually form large islands, which affects
the formation of interpenetrating network structure, and the
overall performance of photovoltaic cells decreases. In the
photovoltaic cell of the P3HT: PC61BM blend system, if the
mass ratio of PC61BM is less than 47%, the photovoltaic cell
cannot form an effective electron transmission path. When
the mass ratio of PCBM is higher than 60%, PC61BM aggregates to form a large island structure that hinders the
transmission of electrons and reduces the efficiency of
photovoltaic cells. The experiment found that the best ratio
of P3HT:PC61BM blending system is 1 : 1. The best ratio of
MDMO-PPV:PCBM system and MEH-PPV:PC61BM system is 1 : 4.
4.3. The Influence of Additive DIO on the Performance of
Polymer Devices. In the experiment, 1,8-diiodooctane (DIO)
was used as the interface modifier, and the blend PFO-3ThPz-Tpa: PC61BM (wt%, 1 : 3) used chlorobenzene as the
solvent. A small amount of DIO is added to the polymer
blend solution, the volume percentage of DIO and chlorobenzene (CB) is 0%, 2%, 4%, and 8%, the concentration of
the solution is 24 mg/mL, and the thickness of the active
layer is about 95 nm, the annealing temperature is 150°C,
and the annealing time is 15 min. The phase separation and
nanomorphology of the obtained bulk heterojunction
polymer fullerene film are improved.
Table 2 lists the performance parameters of the device
doped with different proportions of DIO. From the table, it
can be seen that the additive DIO has a significant effect on
the fill factor and efficiency of the device. When the proportion of additives is 2%, the fill factor reaches the maximum FF � 0.43, and the efficiency is increased by 12%
compared with the absence of additives. As the proportion of
additives increases, the efficiency begins to decrease, and the
fill factor also begins to decrease. This is due to the addition
Advances in Materials Science and Engineering
9
Figure 13: PFO-3-ThPz-Tpa blend AFM morphology of different solvents.
Table 1: Blended photovoltaic parameters of P3HT/PC61BM under different ratios.
P3HT/PC61BM
1 :1
12
1:3
1:4
J (mA/cm2)
12.21
10.85
8.09
7.14
V
0.65
0.68
0.78
0.85
%
4.08
3.85
2.75
2.39
FF
0.51
0.52
0.44
0.38
Table 2: Photovoltaic parameters of doped different ratios of DIO.
DIO:CB
0
2%
4%
8%
J (mA cm2)
7.52
7.48
7.24
6.23
of DIO, and the donor and acceptor form an interpenetrating network structure, forming an effective twophase separation structure; with the increase in the amount
of DIO, the interface contact area between the donor and
acceptor is reduced, resulting in stimulation. The separation
efficiency of electrons and the transmission efficiency of
holes (electrons) are reduced. It can be seen from Figure 14
that the interface morphology changes after the addition of
DIO. In addition, the addition of a relatively high proportion
of additives is equivalent to increasing the amount of traps in
the active layer, which in turn reduces the performance of
the device.
4.4. The Influence of Different Cathode Interface Modification
Layers on the Performance of Polymer Devices. The physical
properties such as humidity and interlayer adhesion of organic
and inorganic materials have an important impact on the life
and performance of the device. However, in the development
of organic photovoltaic devices, the influence of the morphology and charge extraction/recombination of the electrode/
organic interface film is often ignored. PCBM is used as the
acceptor material, and the polymer PFO-FCz-DBT30 is used as
the donor. The structural formula is shown in Figure 15. The
ultraviolet absorption spectrum is shown in Figure 16.
V
0.76
0.74
0.75
0.75
FF
0.37
0.44
0.38
0.36
%
2.09
2.35
1.98
1.69
PFO-FCz-DBT30 has two strong absorption peaks at
393 nm and 532 nm. The experimentally measured LUMO
and HOMO energy levels of the polymer PFO-FCz-DBT30
are ELUMO � − 3.34 eV, EHOMO � − 5.22 eV, Egel � 1.68 eV,
and Egopt � 1.87 eV, respectively.
The dark current-voltage and photocurrent-voltage
characteristics of the device are all tested by Keithley 2602.
The light source is AM1.5G 100 mW/cm2, and the test
process is carried out under ambient room temperature
conditions of 48 atmospheres. The photovoltaic characteristic parameters of the device are shown in Table 3.
It can be seen from the table that with the introduction of
LiF and CsF interface modification layers, the Voc of the
device has been improved, but the Jsc has decreased. In
electroluminescent devices, there are related literature reports that inserting a LiF interface modification layer between the polymer layer and the Al electrode layer can
increase the stability of the device and reduce the electron
injection barrier in OLEDs.
In the experiment, we found that in PFO-FCz-DBT30 the
open-circuit voltage of the PCBM blend system photovoltaic
device is not ELUMO(A)-EHOMO(D) � െ3.91 eV(5.22 eV),
nor is it a two-electrode work function. The difference between ITO/PEDOT work function is 5.1∼5.2 eV, but is
somewhere in between.
10
Advances in Materials Science and Engineering
Figure 14: CB AFM image for solvent.
C8H17
C8H17
N
N
C8H17
S
C8H17
N
N
S
S
C8H17
y
C8H17
Figure 15: PFO-FCz-DBT30 molecular structure diagram.
2
1.8
Normalized ansorbance
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
300
400
500
600
700
Wavelenth
PFO-FCZ-DBT30
Figure 16: Ultraviolet absorption spectrum of PFO-FCz-DBT30.
Table 3: Different modified interfaces and performance parameters of photovoltaic devices.
Interface modification
NO
LiF
Ca
CsF
J
4.56
4.36
3.74
4.23
V
0.66
0.8
0.77
0.87
FF
0.23
0.26
0.26
0.27
%
0.65
0.9
0.78
0.99
Advances in Materials Science and Engineering
11
5. Conclusions
At present, the highest energy conversion efficiency of organic photovoltaic cells has reached 10.0 ± 0.3%. With the
development of technology, batteries with higher energy
conversion efficiency will be developed. At that time, lowpower electronic products will get rid of the charging
problem, and people’s lives will be more convenient. Organic photovoltaic cells have the advantages of lightweight,
softness, and foldability. Organic photovoltaic cells can be
designed into various shapes, which are convenient to carry
and have certain practical value. Organic photovoltaic cells
are bound to highlight their incomparable competitive
advantages in future energy wars with their superior performance and low cost. In organic photovoltaic devices,
controlling the morphology of the active layer and improving the contact between the interfaces to form ohmic
contacts is of great significance to the improvement of device
performance. To improve the performance of organic
photovoltaic devices, the selection of materials and the
optimization of the devices complement each other and are
indispensable.
[9]
[10]
[11]
[12]
[13]
[14]
Data Availability
No data were used to support this study.
Conflicts of Interest
[15]
[16]
The author declares that there are no conflicts of interest
regarding the publication of this article.
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