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arXiv · 2608.17577

Operando multidimensional spectroscopy reveals A-site-dependent carrier cooling in perovskite solar cells

Edoardo Amarotti·Luca Bolzonello·Qi Shi·Sun-Ho Lee·Torbjörn Pascher·Donatas Zigmantas·Niek van Hulst·Nam-Gyu Park·Tönu Pullerits
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Abstract

Understanding how photogenerated carriers dissipate excess energy in operating perovskite solar cells is essential for connecting ultrafast photophysics with photovoltaic function and provides design principles for engineering next-generation cell architectures. Here we use photocurrent-detected two-dimensional electronic spectroscopy (PC-2DES) to resolve energy-dependent carrier relaxation in fully encapsulated, functioning metal halide perovskite solar cells. By comparing devices with identical architecture but different absorber compositions - MAPbI3, mixed FAMA, and FAPbI3 - we directly follow the redistribution of photoexcited carriers from initially populated high-energy states toward lower-energy band-edge states. The multidimensional photocurrent response reveals a cascade-like intraband cooling process whose rate depends strongly on absorber composition, with the slowest relaxation in MA-based devices, intermediate behaviour in mixed-cation devices, and fastest relaxation in FA-based devices. A reduced kinetic model incorporating phonon-mediated intraband scattering, supplemented by a phenomenological many-body contribution, captures the main energy-dependent trends. These results establish action-detected multidimensional spectroscopy as a device-level probe of ultrafast energy dissipation and show that subtle changes in perovskite composition can substantially reshape the carrier relaxation pathways that precede charge extraction.

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Edoardo Amarotti, Luca Bolzonello, Qi Shi, Sun-Ho Lee, Torbjörn Pascher, Donatas Zigmantas, Niek van Hulst, Nam-Gyu Park, Tönu Pullerits. 2026-08-18. Operando multidimensional spectroscopy reveals A-site-dependent carrier cooling in perovskite solar cells. https://arxiv.org/abs/2608.17577

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