Small Molecule Regulatory Strategy for Inorganic Perovskite Solar Cells with 368 mV of V_OC Deficit and its Application in Tandem Devices

Tandem solar cells combining perovskite and silicon have witnessed rapid development in recent years. However, the top cell, utilizing wide-bandgap perovskite as absorbers generally suffer significant open-circuit voltage (V-OC) deficit, particularly for inorganic perovskite, which poses a considerable obstacle to enhancing the power conversion efficiency (PCE). Here, a modulation strategy by using 2,6-pyridinedicarboxamide (PC), the crystallization kinetics of inorganic perovskite film can be effectively regulated, specifically manifested as a relatively longer annealing time in the air, resulting in sufficient growth for the inorganic perovskite grains. Additionally, PC can effectively in situ passivate uncoordinated Pb2+, suppressing the non-radiative recombination of charge carriers. Eventually, a record PCE of 22.07% is achieved based on n-i-p inorganic perovskite solar cells (IPSCs), which also demonstrate the highest V-OC above 1.34 V (1.71 eV of bandgap). More importantly, the unencapsulated IPSCs show enhanced thermal stability and photostability. Furthermore, the n-i-p IPSCs are also applied to inorganic perovskite/silicon tandem solar cells (IPTSCs), a PCE of 27.27% and an impressive V-OC of 2.024 V are obtained.