Room‐Temperature Surface Sulfurization for High‐Performance Kesterite CZTSe Solar Cells

Abstract

The interfaces are very important for kesterite‐structured solar cells. In this study, a facile room temperature chemical sulfurization process is developed to modify the surface of the CZTSe films, which can prevent the decomposition of kesterite film at high temperature during the traditional sulfurization process and thus introducing the deep defects in the absorber layer. It is found that the (NH4)2S vapor sulfurizes the surfaces of the CZTSe thin films previously etched by ammonia. Consequently, the surface defects are passivated by the incorporated sulfur, and the interfacial band alignment is improved at the junction. The open circuit voltage (VOC) of the solar cell device is improved from 364 mV to 406 mV, with the cell efficiency increased to 9.04% when the (NH4)2S vapor treatment time is optimized at 25 min. This study affords a new perspective for enhancing the performance of kesterite‐based thin film solar cells using a facile surface sulfurization approach.

Na-doping-induced modification of the Cu2ZnSn(S,Se)4/CdS heterojunction towards efficient solar cells

“…However, the CZTSSe efficiency record is only 12.6% whereas the efficiency of CIGS solar cell has recently reached 23.35% [4][5][6]. Recently, people have indeed borrowed some strategies from CIGS to improve the performance of CZTSSe solar cells [2,[7][8][9][10][11][12][13][14][15]. For example, alkali metal doping of CIGS can improve the crystallinity of the absorber [16,17], reduce the density of point defects and increase the P-type carrier concentration [18,19].…”

Nanoscale Surface Electrical Properties Tailored by Room‐Temperature Sulfurization for High‐Efficient CZTSe Solar Cells

“…Previous study indicates that the content of sulfur incorporation is low with such room‐temperature surface sulfurization treatment. [ 15 ] So the significant improvement of V OC is not only because of the increase of bandgap, but also from the improvement of the surface nanoscale electrical properties, which will be discussed below. In addition, it should be noted that all the photovoltaic parameters of the Cell Ref.+NH 4 OH+AS show the smallest standard deviation among these three kinds of solar cells.…”

“…The detailed experimental process of (NH 4 ) 2 S vapor treatment can be found in ref. [ 15 ] . CZTSSe solar cells after surface treatment were fabricated with the process described in ref.…”

“…CZTSSe solar cells after surface treatment were fabricated with the process described in ref. [ 15 ] . The active area of each CZTSSe solar cell is 0.12 cm 2 .…”

“…Thus, this method is considered as a potential approach for the sulfurization of CZTSe film. [ 15 ] However, the dynamics of sulfurization is very poor at room temperature, the reasons why such approach can realize the sulfurization for CZTSe film and why the performance of the solar cells can be improved are still unclear, which limits the understanding of surface bandgap engineering at room temperature and restricts the further enhancement of the performance of kesterite‐based thin film solar cells as well as other Se‐ or S‐containing solar cells.…”