Device Characteristics of Bandgap Tailored 10.04% Efficient CZTSSe Solar Cells Sprayed from Water Based Solution

摘要： Diverse S/(S+Se) ratio of Cu2ZnSn(Sx,Se1–x)4 (CZTSSe) thin film solar cells fabricated by water based spray pyrolysis approach. By fine tuning the S/(S+Se) ratio, base CZTSSe device efficiency has significantly improved from 7.02% to 10.04% by minimizing the Voc deficit up to 616 mV and increasing FF from 56.42% to 62.38%. As S/(S+Se) ratio was increased from 0 to 0.4, surface compactness was observed to be improved with slightly decreased grain size, which increased shunt resistance and resultantly increased fill factor. However, S-alloying more than S/(S+Se)=0.4, grain size was too much decreased and had detrimental effect on device performance. To deeply understand the role effect of S/(S+Se) ratio, detailed spectroscopic analysis performed with admittance spectroscopy (AS), temperature dependent current-voltage characteristic (J-V-T), time-resolved photoluminescence (TRPL) and Raman depth profiling. Experimental results revealed that the different power conversion efficiency (PCE) limiting factors were developed with various S/(S+Se) ratio. High density of deep defect states generated with S/(S+Se) ≥ 40% content and larger conduction band offset observed with red kink were formed in the Se/(S+Se) ≥ 80% content. Hence, in order to get high efficient CZTSSe solar cell, fine tuning of S/(S+Se) ratio is necessary.