Single-Particle Organolead Halide Perovskite Photoluminescence as a Probe for Surface Reaction Kinetics.

Photoluminescence (PL) of organolead halide perovskites (OHPs) is sensitive to OHPs' surface conditions and is an effective way to report surface states. Literature has reported that at the ensemble level, the PL of photoexcited OHP nanorods declines under an inert nitrogen (N2) atmosphere and recovers under subsequent exposure to oxygen (O2). At the single-particle level, we observed that OHP nanorods photoblink at rates dependent on both the excitation intensity and the O2 concentration. Combining the two sets of information with the charge-trapping/detrapping mechanism, we are able to quantitatively evaluate the interaction between a single surface defect and a single O2 molecule using a new kinetic model. The model predicts that the photodarkening of OHP nanorods in the N2 atmosphere has a different mechanism than conventional PL quenching, which we call photo-knockout. This model provides fundamental insights into the interactions of molecular O2 with OHP materials and helps design a suitable OHP interface for a variety of applications in photovoltaics and optoelectronics.