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

Abstract

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 (J_SC) and open circuit voltage (V_OC) simultaneously. We have designed a double-absorber solar cell based on AgSb(S,Se)₂, whose structure is glass/ITO/CdS/AgIn_0.5Sb(S,Se)_2.75/AgSb_1.25(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 V_OC of 0.396 V, a J_SC 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 AgIn_0.5Sb(S,Se)_2.75 and an 850 nm thickness of AgSb_1.25(S,Se)_2.375 stacked from bottom to top. A high J_SC, which was attributed to AgIn_0.5Sb(S,Se)_2.75, was achieved, and the V_OC was almost maintained at the same level as that of AgSb_1.25(S,Se)_2.375. This strategy may provide a new approach to unravel the contradiction between high J_SC and high V_OC, which could be utilized in other solar cells.