Supplementary materials
Exploiting metallic glasses for 19.6 % efficient
back contact solar cell
Suk Jun Kim, Se Yun Kim, Jin Man Park, Jung Na Heo, Jun Ho Lee, Sang Mock Lee, Do Hyang Kim1, Won
Tae Kim2, Ka Ram Lim1, Donghwan Kim3, Sung Chan Park4, Hyoeng Ki Kim4, Min Chul Song4, Jucheol Park5,
Sang Soo Jee*, Eun-Sung Lee*
S1. Fabrication of Ag electrode
Synthesis of metallic glass (MG) frits and ribbons
The metallic glass frits used in this study were obtained by an inert gas atomization process. The master alloy
ingot (~3 kg) was prepared by arc-melting of a mixture of constituent elements with purity better than 99.9% in
a Ti-gettered argon atmosphere. The resulting master alloy ingot was atomized using an atomizer in the Korea
Institute of Industrial Technology (KITECH). The frits were sieved to obtain frits of under 5 μm. MG ribbons
were produced using a melt-spinning process in an Ar atmosphere. Typical ribbons produced were 40 μm thick
and 5 mm wide. Compositions and impurities of both the frits and ribbons were confirmed in inductively
coupled plasma (ICP). Their thermal properties were analyzed with differential scanning calorimetry (DSC) at a
heating rate of 40 K/min in an Ar atmosphere. X-ray diffraction analysis confirmed the amorphous nature of the
MG frits and ribbons.
Glass transition temperature (T g), crystallization temperature (Tx), and super-cooled
liquid region (SCLR) of Al84.5Y10Ni5.5, Al85Y8Ni5Co2, and Al86Ni6Y4.5Co2La1.5 frits provided in Table I were
measured in DSC and crystallinity of MG frits was confirmed by x-ray diffraction (XRD) as shown in Table SI.
Glass forming ability (GFA) of the frits were compared to the one measured from ribbons.
Table SI. Summary of GFA and SCLR of Al MG frits
Fig. S1. A part of the Ag electrodes was sliced into sections with a 200 nm thickness using a focused ion beam
following the normal cross-sectional transmission electron microscopy (TEM) sample preparation method, and
then laid down on a glass slide. Two corners at the bottom of the slice were fixed with Pt coating on the slice so
that it would not move while the nanoprobes were in contact with it. Resistance between the Ag electrode and
the Si emitter was measured using a four-nanoprobe system. Individual contacts were electrically disconnected
each other by ion beam cutting. Measured resistance was multiplied by an interface area to calculate the specific
contact resistance.
The interface area was equal to the slice thickness, 200 nm, multiplied by the width of
individual contacts. The resistance was assumed to be equal to the contact resistance because resistances from
Ag and Si were negligible. After the measurement, the Pt coatings at the bottom of the slice were removed and
the slice was transferred from the glass slide onto a TEM grid and the interlayer thickness between the electrode
and the emitter was measured in TEM.
Table SII. Summary of direct measurement of specific contact resistances
Interlayer thickness (nm)
Specific contact resistance( mΩcm2)
10 ± 0.8
0.1
12 ± 1.9
0.2
16 ± 1.5
1.0
18 ± 0.9
5.8
Fig. S2. Depth profiling of Al diffused into Si substrate after the firing was analyzed in secondary ion mass
spectrometry (SIMS). The sample for SIMS was prepared by etching the Ag electrode with Nitric acid and
hydrofluoric acid followed by cleaning with DI water.
Fig. S3. Macroscopic specific contact resistances were measured at various temperatures. Temperature
independence of tunneling barrier heights was confirmed by this measurement and summarized in Table SIII.
transmission line model pattern was screen-printed with using the Ag paste with Al84.5Y10Ni5.5 MG frits on Si
substrate and it was liquid N2 cooled in vacuum. By inputting the measured resistances and temperatures into
Eq. 2, the tunneling barriers at the various temperatures were calculated. In this calculation, the average
thickness of the interlayer was 15.6 nm, which was calculated with using Eq. 2 based on 0.34 of contact area
and 35 meV of tunneling barrier at RT.
Table SIII. Summary of relationship between temperature and tunneling barrier height
Temperature (K)
ρc (mΩ·cm2)
Tunneling barrier height (meV)
300
1.58
35.1
240
2.85
37.6
200
3.10
36.9
160
4.43
37.8
120
3.31
34.0
80
8.15
37.3