Multi-cation synergy improves crystallization and antioxidation of CsSnBrfor lead-free perovskite light-emitting diodes.

Tin (Sn) perovskites have emerged as promising alternatives to address the toxicity concerns associated with lead-based (Pb) perovskite light-emitting diodes (PeLEDs). However, the inherent oxidation of Sn perovskite films leads to a serious efficiency roll-off in PeLEDs at increased current densities. Although three-dimensional CsSnBrperovskites exhibit decent carrier mobilities and thermal stability, their rapid crystallization during solution processing results in inadequate surface coverage. This inadequate coverage increases non-radiative recombination and leakage current, thereby hindering Sn PeLED performance. Herein, we present a multi-cation synergistic strategy by introducing the organic cations formamidinium (FA) and thiophene ethylamine (TEA) into CsSnBrperovskites. The addition of organic cations delays crystallization by forming hydrogen bonds interacting with the CsSnBr. The smaller FAenters the perovskite lattice and improves crystallinity, while the larger TEAcation enhances surface coverage and passivates defect states. By further optimizing the interface between PEDOT:PSS and perovskite layers through the use of ethanolamine and a thin layer of LiF, we achieved a red Sn-based PeLED with an emission wavelength of 670 nm, a maximum luminance of 151 cd m, and an external quantum efficiency of 0.21%.