Pseudohalide-Modulated Crystallization for Efficient Quasi-2D Tin Perovskite Solar Cells with Minimized Voltage Deficit

Regulating the crystallization dynamics and suppress-ing the oxidation of Sn2+ is imperative for the emerging lead-free tin perovskite solar cells (TPSCs). In this respect, quasi-2D tin perovskites exhibit relatively slow crystallization and crystal growth rate compared to the three-dimensional analogues. However, these dimensional-mixed tin perovskites suffer from random orientation, which limits the charge carrier transport for photovoltaic applications. Herein, we report a facile and feasible strategy to modulate the dimensionality and crystallization of tin perovskites with the incorporation of phenethylammonium thiocyanate (PEASCN), which is exploited to deliver a high-quality crystal growth and preferred alignment. The pseudohalide SCN- can effectively hinder Sn2+ oxidation by synergistically modulating the coordination and crystal growth of Sn perovskite films. Meanwhile, these interactions significantly suppressed the nonradiative charge recombination. Finally, a high efficiency approaching 12.88% with an open-circuit voltage (Voc) of 863 mV is achieved for the inverted TPSCs. The obtained Voc is among the highest reported values for indene-C60 (ICBA)-free TPSC devices. The PEASCN devices also exhibited high stability for over 2000 h under a N2 atmosphere.

Automated summary

Regulating the crystallization dynamics and suppress-ing the oxidation of Sn2+ is crucial for improving the efficiency of lead-free tin perovskite solar cells. This study presents a facile strategy to modulate the dimensionality and crystallization of tin perovskites using phenethylammonium thiocyanate (PEASCN). The incorporation of PEASCN results in high-quality crystal growth and preferred alignment, while effectively inhibiting Sn2+ oxidation and suppressing nonradiative charge recombination. The TPSCs fabricated using this strategy achieved a high efficiency of 12.88%, with a Voc of 863 mV, and exhibited great stability for over 2000 hours under a N2 atmosphere.