High-Efficiency Confined Magnetic Bipolaron Emission in Mn ²⁺ -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 Mn 2+ -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.