Publication date: 11th March 2026
Wide-bandgap halide perovskites are essential for high-voltage and tandem photovoltaic architectures, where maximizing quasi-Fermi-level splitting is critical for minimizing voltage losses [1,2]. Transient photoluminescence (TPL) spectroscopy is widely used to probe carrier recombination dynamics in these materials. Here, we present a comprehensive numerical and analytical investigation of sub-band radiative recombination in wide-bandgap perovskites. Experimentally, sub-band emission exhibits markedly slower decay dynamics than band-edge photoluminescence [3], indicating carrier localization and delayed recombination mediated by deep trap states. To elucidate the underlying mechanisms, we develop a physics-based carrier-dynamics model that explicitly incorporates band-to-band radiative recombination, carrier trapping and emission, and a radiative trap-to-band recombination pathway.
The coupled rate equations are solved under pulsed excitation conditions [4], enabling a unified and self-consistent description of both band-edge and sub-band emission within a radiative recombination framework. This model allows clear identification of the dominant recombination channels governing the observed TPL dynamics. Model-based fitting of transient photoluminescence decays quantitatively extracts band-to-band and trap-to-band radiative recombination parameters, accurately reproducing both the power-law decay of band-edge emission and the slower sub-band photoluminescence kinetics governed by trap occupancy.
Overall, this work establishes a rigorous theoretical foundation for interpreting sub-band photoluminescence in TPL studies and provides defect-aware insights critical for voltage optimization in wide-bandgap perovskite photovoltaic devices.
The authors acknowledge National Center for Photovoltaics Research and Education (NCPRE), IIT Bombay. Author also thank the Directorate of Technical Education (DTE), Kerala,
and the All India Council for Technical Education (AICTE) for supporting this work through the QIP fellowship.
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