A/B-site synergistic engineering in nanoscale quasi-two-dimensional perovskites: Bimetallic Cs+ /Cd2+ co-doping for enhanced luminescence and phase stability of BA2MAn-1PbnBr3n+1films

The development of quasi-two-dimensional (quasi-2D) perovskite films with high photoluminescence quantum yield (PL QY) and robust environmental stability remains a critical challenge for advanced optoelectronic applications. Herein, we report an A/B-site synergistic doping strategy by incorporating multivalent Cs + (A-site) and Cd 2+ (B-site) ions into quasi-2D BA 2 MA n-1 Pb n Br 3n+1 films, significantly enhancing their optical quality and structural stability. Notably, the bimetallic ion-doped films achieve a high PL QY of up to 90 % at 490 nm, along with excellent homogeneous phase stability (the phase separation of quasi-2D films emitting at 435 nm and 490 nm is suppressed even after 1 h and 10 h). Moreover, co-doping with multivalent Cs + and Cd 2+ ions induces a significant reduction in both grain size (10–15 nm) and surface roughness (∼1 nm), while endowing the quasi-2D films with a high exciton binding energy (>300 meV). The variable temperature PL spectra reveal the band-edge radiative dynamics, which originate from the thermal competition between exciton and trap-mediated recombination. The heat-induced electron-phonon interaction enhances the proportion of trap-mediated recombination, leading to an increase in the average PL lifetime. The A/B-site synergistic engineering provides a novel approach for improving the PL performance and photostability of quasi-2D perovskite films, paving the way toward high-performance light-emitting diodes, lasers, and other ptoelectronic devices based on the luminescent layer.