High-Efficiency Confined Magnetic Bipolaron Emission in Mn2+-Doped 2D Benzimidazolium Lead Chloride.

Two-dimensional (2D) organic-inorganic hybrid perovskites hold great promise for optoelectronics, yet their practical performance is severely limited by photoluminescence (PL) thermal quenching from strong electron-phonon coupling in soft lattices. Here, we report a confined magnetic bipolaron strategy to achieve efficient, thermally stable PL in Mn2+-doped 2D benzimidazolium lead chloride perovskite. Via synergy of directional coordination, interlayer confinement, and hydrogen bonding, we form ferromagnetically coupled Mn-Cl-Mn pairs as confined magnetic bipolaron emission centers, moderating electron-phonon coupling and suppressing nonradiative recombination. The optimized material shows 623 nm orange-red emission with 96.9% room-temperature PLQY, 99.6% color purity, and 84% peak intensity retention at 400 K. This work opens a new route to stabilize photoexcited states for high-performance perovskite emitters.