Can photoluminescence quenching be a predictor for perovskite solar cell efficiencies?

Bromide-based perovskites have large bandgaps, making them attractive for tandem solar cells developed to overcome the Shockley-Queisser limit. A perovskite solar cell architecture employs transporting layers to improve charge extraction and transport. Due to the wide variety of materials and preparation methods, it is critical to devise fast screening methods to rank transporting layers. Herein, we evaluate perovskite fluorescence quenching followed by time- and energy-resolved photoluminescence (TER-PL) and analyse the intensity dependence as a potential method to qualify charge-transporting layers rapidly. The capability of the technique was evaluated with TiO/FAPbBr and SnO/FAPbBr, the most commonly used electron transporting layers, which were prepared using standard protocols to make best-performing devices. The results revealed that TiO is the most effective quencher due to the higher density of states in the conduction band, consistent with Marcus-Gerischer's theory. However, record-performance devices use SnO as the electron transport layer. This shows that the relationship between photoluminescence quenching and device performance is not bidirectional. Therefore, additional measurements like conductivity are also needed to provide reliable feedback for device performance.