Guanidinium Thiocyanate Additive Engineering for High-Performance CsPbIBr2 Solar Cells with an Efficiency of 10.90%

Using additives to adjust the morphology of perovskite films is an effective method to improve the power conversion efficiency (PCE) and long-term stability of CsPbIBr2 perovskite solar cells (PSCs). In this work, CsPbIBr2 films are modified with the guanidinium thiocyanate (GuaSCN) additive. After adding GuaSCN into the precursor of perovskite, the crystal quality of the resulted perovskite films improved, and the orientations of the (100) and (200) crystal planes are enhanced obviously. The energy level alignment is optimized, which is beneficial to the extraction of electrons. Moreover, the defect density is reduced, and the charge recombination process is effectively suppressed, thereby improving the solar cell efficiency and stability. GuaSCN is absent from the resulted perovskite film due to the high-temperature annealing. Consequently, based on the GuaSCN additive with a 3% molar ratio in the perovskite precursor solution, the device yields a champion PCE of 10.90%, with an open-circuit voltage of 1.23 V, a short-circuit current of 12.05 mA/cm2, and a fill factor of 73.71%, which is 18.7% higher than that of the counterpart without GuaSCN. The improved CsPbIBr2 PSC shows better stability. The PCE retains ∼95% of its initial value compared to only ∼64% for pristine PSCs after being stored for over 600 h without encapsulation in air. This work provides a facile strategy for reducing defects and improving the performance of all-inorganic PSCs.