Large and Small Polarons in Highly Efficient and Stable Organic-Inorganic Lead Halide Perovskite Solar Cells: A Review

Polarons, which arise from the intricate interplay between excess electrons and/or holes and lattice vibrations (phonons), represent quasiparticles pivotal to the electronic behavior of materials. This review reaffirms the established classification of small and large polarons, emphasizing its relevance in the context of recent advances in understanding lead halide perovskites' behavior. The distinct characteristics of large and small polarons stem from the electron-phonon interaction range, which exerts a profound influence on materials' characteristics and functionalities. Concurrently, lead halides have emerged with exceptional opto-electronic properties, featuring prolonged carrier lifetimes, low recombination rates, high defect tolerance, and moderate charge carrier mobilities; these characteristics make them a compelling contender for integration of optoelectronic devices. In this review, the formation of both small and large polarons within the lattice of lead halide perovskites, elucidating their role in protecting photogenerated charge carriers from recombination processes, is discussed. As optoelectronic devices continue to advance, this review underscores the importance of unraveling polaron dynamics to pave the way for innovative strategies for enhancing the performance of next-generation photovoltaic technologies. Future research should explore novel polaronic effects using advanced computational and experimental techniques, enhancing our understanding and unlocking new applications in materials science and device engineering. Polarons, arising from electron--phonon interactions, are crucial to materials' electronic behavior. This review classifies large and small polarons in lead halide perovskites, highlighting their impact on charge carrier protection, recombination rates, and optoelectronic properties. It underscores the importance of polaron dynamics in improving photovoltaic technologies and suggests future research avenues.image (c) 2024 WILEY-VCH GmbH