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Investigation of Surface Sulfurization in CuIn 1− x Ga x S 2− y Se y Thin Films by Using Kelvin Probe Force Microscopy
Author(s) -
Kim Haeri,
Park Se Jin,
Kim Byungwoo,
Hwang Yun Jeong,
Min Byoung Koun
Publication year - 2018
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201701019
Subject(s) - kelvin probe force microscope , band gap , passivation , thin film , surface photovoltage , solar cell , work function , band bending , materials science , analytical chemistry (journal) , absorption (acoustics) , chemistry , optoelectronics , nanotechnology , atomic force microscopy , composite material , spectroscopy , physics , layer (electronics) , quantum mechanics , chromatography
CuIn 1− x Ga x S 2− y Se y (CIGSSe) thin films have attracted a great deal of attention as promising absorbing materials for solar cell applications, owing to their favorable optical properties (e.g. a direct band gap and high absorption coefficients) and stable structure. Many studies have sought to improve the efficiency of solar cells using these films, and it has been found that surface modification through post‐heat treatment can lead to surface passivation of surface defects and a subsequent increase in efficiency. The surface properties of solution‐processed CIGSSe films are considered to be particularly important in this respect, owing to the fact that they are more prone to defects. In this work, CIGSSe thin films with differing S/Se ratios at their surface were synthesized by using a precursor solution and post‐sulfurization heat treatment. These CIGSSe thin films were investigated with current–voltage and Kelvin probe force microscope (KPFM) analyses. Surface photovoltage (SPV), which is the difference in the work function in the dark and under illumination, was measured by using KPFM, which can examine the screening and the modification of surface charge through carrier trapping. As the concentration of S increases on the CIGSSe film surface, higher work functions and more positive SPV values were observed. Based on these measurements, we inferred the band‐bending behavior of CIGSSe absorber films and proposed reasons for the improvement in solar cell performance.