Efficiency Improvement of Flexible Cu₂ZnSn(S,Se)₄ Solar Cells by Window Layer Interface Engineering

Abstract

Flexible Cu 2 ZnSn(S,Se) 4 (CZTSSe) solar cells have wide application prospects. N-type window layers and contact among the layers have an important effect on the properties of flexible CZTSSe solar cells. Here, we present a modified structure for flexible CZTSSe solar cells with window layers (CdS/ITO) instead of the traditional window layers (CdS/ZnO/ITO) for higher performance and lower cost. The flexible CZTSSe device realizes 9.2% efficiency with an improved fill factor (FF) from 57.7 to 63.6%. Systematic physical measurements show that the increase in FF comes from a significant decrease in series resistance (R s ). To enhance the antireflective function of the window layers, we introduce MgF 2 antireflection coatings on the surfaces of solar cells. The average J sc of devices is significantly enhanced 6% due to the antireflective effect. A champion device achieves an efficiency of 9.7% with the highest FF of 64.0% in the flexible CZTSSe solar cells. The present investigation will provide a new strategy for the development of flexible CZTSSe solar cells.

Precursor solution chemistry via water additive enabling CZTSSe solar cells with over 12% efficiency

“…The detailed parameters are summarized in Table 1. The reduction in the diode factors, including G sh , R s , A, and J 0 , reveals CZTSSe absorbers with high quality and clearly indicates the much lower recombination rate of photogenerated carriers, producing an important enhancement in J sc , FF, and hence PCE [34,35].…”

A Progress Review on Challenges and Strategies of Flexible Cu2ZnSn(S, Se)4 Solar Cells

“…In recent years, the power conversion efficiency (PCE) of FCSs has developed rapidly and has exceeded 11%, as shown in Figure 1b. In the research, flexible glass, [ 39 ] polyimide, [ 40,41 ] and metal foils [ 42–69 ] are used as flexible substrates. The FCSs reported in recent years are mostly fabricated on Mo foils, stainless steel (SS) foils, and Ti foils.…”

9.3% Efficient Flexible Cu2ZnSn(S,Se)4 Solar Cells with High‐Quality Interfaces via Ultrathin CdS and Zn0.8Sn0.2O Buffer Layers

“…Therefore, thinning the CdS layer leads to an increase in the R s of the device, indicating an unfavorable charge transport process, and the large R s is detrimental to the FF of the device as well as degrades the device performance. [ 28–32 ] When the CdS layer is further thinned from 10 to 0 nm, the PCE of the device drops sharply from 5.3% to 1.0%. The R s of the device increases slightly, while the G sh increases obviously from 1.94 to 62.21 mS cm −2 .…”

“…The CZTSSe film was prepared on the Mo foil by spin coating and selenization annealing as our previous report. [ 28 ] The CdS film (60 nm) was prepared by the CBD method. The ZnO layer (≈50 nm) and the ITO layer (≈220 nm) were prepared by RF sputtering, respectively.…”