Unveiling the underlying spin mechanism in quasi-2D perovskite spin-polarized lasing

Spin-polarized lasers hold great potential in integrated photonic devices for secure communication, optical interconnections, and advanced optical devices, offering excellent properties superior to those of conventional lasers. Quasi-two-dimensional (quasi-2D) perovskites are promising candidates for spin-polarized lasers, because their potential structural inversion asymmetry will result in strong spin-orbit coupling (SOC) facilitating spin injection and hence spin splitting of electronic bands. However, strong SOC involves a trade-off between spin injection and spin lifetimes. How to prolong spin lifetimes in the lasing regime while maintaining the optical gain make it challenging to sustain spin polarization for lasing. Here, we unveil the underlying spin mechanism and successfully realize quasi-2D perovskite spin-polarized lasing by suppressing fast spin relaxation through triplet exciton regulation using organic cations of phenylethylammonium (PEA) and 1-naphthylmethylamine (NMA). We identify the Bir-Aronov-Pikus (BAP) mechanism is the dominant spin relaxation mechanism preventing the achievement of spin-polarized lasing in quasi-2D perovskites. By modulating the reverse intersystem crossing of triplet excitons, the D’yakonov-Perel’ (DP) mechanism becomes to play a key role and results in a new-emerged prolonged spin lifetime of 35.4 ps at 77 K, which is ∼5 times that of the BAP-induced one. Consequently, spin-polarized lasing is realized below 200 K, and the threshold is 30.2% lower than that for linearly polarized excitation. This work underscores the potential of PEA-based quasi-2D perovskites in spin-polarized lasing and contributes to the rapid advancements in perovskite spintronic devices.