Strategy of stacking double absorbers to gain high efficiency in silver antimony sulfide selenide-based thin film solar cell

Silver antimony sulfide (AgSbS2) is used as an absorption layer in thin film solar cells due to its suitable bandgap and economic considerations. Efforts have been made to improve the photovoltaic performance of devices, but it is difficult to increase the short circuit current (JSC) and open circuit voltage (VOC) simultaneously. We have designed a double-absorber solar cell based on AgSb(S,Se)2, whose structure is glass/ITO/CdS/AgIn0.5Sb(S,Se)2.75/AgSb1.25(S,Se)2.375/Au. Ultrasonic spray pyrolysis was used to prepare the films, and a selenization process was conducted to construct a gradient band structure. The two stacked absorbers have a total thickness of 1700 nm. The best performance obtained had a VOC of 0.396 V, a JSC of 17.04 mA cm−2, a fill factor (FF) of 52.78%, and an efficiency of 3.57%. The champion device had a double layer design with an 850 nm thickness of AgIn0.5Sb(S,Se)2.75 and an 850 nm thickness of AgSb1.25(S,Se)2.375 stacked from bottom to top. A high JSC, which was attributed to AgIn0.5Sb(S,Se)2.75, was achieved, and the VOC was almost maintained at the same level as that of AgSb1.25(S,Se)2.375. This strategy may provide a new approach to unravel the contradiction between high JSC and high VOC, which could be utilized in other solar cells.