Photoluminescence Quantum Yield in Perovskite Solar Cells: Probing Interface Recombination and Efficiency Limits

This review surveys recent advances in employing photoluminescence quantum yield (PLQY) as a quantitative probe in perovskite solar cells (PSCs), highlighting its unique ability to diagnose interfacial nonradiative recombination, reconstruct quasi‐Fermi‐level splitting (QFLS), and anticipate efficiency limits. After presenting the theoretical framework that converts PLQY into QFLS so that it can be directly benchmarked against the device open‐circuit voltage (), we clarify the complementarity between PLQY and conventional time‐resolved photoluminescence. Representative case studies then illustrate how PLQY pinpoints recombination losses at the perovskite/electron‐transport‐layer and perovskite/hole‐transport‐layer interfaces and how targeted passivation strategies simultaneously enhance PLQY, QFLS, and overall device efficiency. The review also discusses how illumination intensity, excitation wavelength, temperature, and humidity influence PLQY measurements and argues that coupling high‐throughput, in situ PLQY mapping with machine‐learning algorithms promises to accelerate the discovery of highly efficient, lead‐free, and stable perovskite materials and devices.