Low‐Temperature Melting–Crystallization Transition in Perovskites With Self‐Trapped Excitons for Photovoltaic Downconversion

Abstract

ABSTRACT Self‐trapped exciton (STE) emitters demonstrate exceptional luminescent downconversion (LDC) performance, achieving near‐unity photoluminescence quantum yields (PLQY) and broadband emission that overcomes Stokes shift limitations in conventional fluorophores. While these properties originate from precisely engineered Jahn–Teller distorted centers through optimized ligand fields and quantum confinement, practical challenges in stability and solution processability have hindered photovoltaic integration. In this work, we develop tin‐halide perovskite exhibiting unique low‐temperature (125°C) reversible melting–crystallization transitions for solution processability, as well as highly efficient (>90% PLQY) broadband LDC through zero‐dimensional STE emission. When integrated as the LDC layer, this reversible melting–crystallization STE emitter enhances the external quantum efficiency of silicon solar cells in the short‐wavelength region, leading to an absolute improvement in power conversion efficiency of over 0.75%. Our findings establish a new paradigm for low‐temperature melt‐processed perovskite integration in silicon photovoltaics, offering both economic viability and scalability for performance enhancement beyond current technological limits.