Applications of Rare‐Earth‐Based Up‐Conversion and Down‐Conversion in Perovskite Solar Cells: A Review

Perovskite solar cells (PSCs) have been considered as one of the most promising photovoltaics, and the power conversion efficiency (PCE) has been boosted to 26.0% in 2023. Extending the spectral absorption range and improving the utilization rate of incident light is one of the effective strategies to further improve the PCE of PSCs. Up‐conversion (UC) and down‐conversion (DC) can convert low‐energy or high‐energy photons into visible light, and the luminesced visible light can be further absorbed by the photoactive layer to generate extra photocurrent. Therefore, UC and DC effects offer the potential of broadening the spectral absorption range and the possibility of overcoming the Shockley–Queisser limit for the single‐junction solar cell. In this review, the spectral‐converting mechanism underling the rare‐earth‐based UC/DC processes is first discussed. Then recent advances in UC/DC applications in PSCs are comprehensively reviewed. Finally, a concise summary and the challenges for the future development of UC/DC in PSCs are outlined.