Supporting Information
Suppression of Surface Recombination in CuInSe2
(CIS) Thin Films via Trioctylphosphine Sulfide
(TOP:S) Surface Passivation
Shi Luo1,*, Carissa Eisler2, Tsun-Hsin Wong3, Hai Xiao4, Chuan-En Lin3, Tsung-Ta Wu5,
Chang-Hong Shen5, Jia-Min Shieh5, Chuang-Chuang Tsai6, Chee-Wee Liu7, Harry A.
Atwater2, William A. Goddard III4, Jiun-Haw Lee3, Julia R. Greer1
1
2
Division of Applied Science and Engineering, California Institute of Technology
Thomas J. Watson Sr. Laboratory of Applied Physics, California Institute of Technology
3
Graduate Institute of Photonics and Optoelectronics and Department of Electrical
Engineering, National Taiwan University
4
Materials and Process Simulation Center, California Institute of Technology
5
6
National Nano Device Laboratories, Taiwan
Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung
University
7
Department of Electrical Engineering, National Taiwan University
*E-mail: slluo@caltech.edu
Figure S1. XPS spectra of In 3d without and with TOP:S treatment for 24 hours under different
temperatures (RT, 80 oC, and 120 oC), showing the binding of TOP:S to CIS surfaces is invariant
of temperature. (b) XPS of spectra of In (b) 3d5/2 and (c) 3d3/2. Black and red lines are measured
peaks as in (a). Blue lines showed the fitted results for In2S3 and In.
Figure S2. (a) STEM image of as-fabricated CIS film. Highlighted region shows the area used
for concentration mapping. (b,c,d) Concentration maps for Na, Cu and Se measured in region
highlighted in (a)
Figure S3. (a) STEM image of passivated CIS film. Highlighted region shows the area used
for concentration mapping. (b,c,d) Concentration maps for Na, Cu and Se measured in region
highlighted in (a)
Figure S4 Low-energy photoelectron spectra of CIS surface before and after TOP:S (120 oC,
24 hours) treatment
Figure S5. Total energy for systems with various levels of NaCu substitution, aligned to pristine
CIS. The Dotted line shows a linear fit of total energy vs. number of Na atoms per 64-atoms
unit cell. The Cross with a dashed line represents the energy change due to one NaCu
substitution in a CIS unit cell with 64 atoms
Figure S6. Optimized structure of the SP(CH3)3 molecule used in DFT calculations to simulate
the effect of TOP:S passivation on film surface. S atom is shown in yellow, P in cyan, C in
brown, and H in white
Figure S7. XPS spectra overview of as-fabricated (black) and passivated (red) CIS films