Open AccessRole of Nonradiative Defects and Environmental Oxygen on Exciton Recombination Processes in CsPbBr3 Perovskite Nanocrystals
Author(s) -
Monica Lorenzon,
Luca Sortino,
Quinten A. Akkerman,
Sara Accornero,
Jacopo Pedrini,
Mirko Prato,
Valerio Pinchetti,
Francesco Meinardi,
Liberato Manna,
Sergio Brovelli
Publication year - 2017
Publication title -
nano letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.853
H-Index - 488
eISSN - 1530-6992
pISSN - 1530-6984
DOI - 10.1021/acs.nanolett.7b01253
Subject(s) - photoluminescence , perovskite (structure) , exciton , quenching (fluorescence) , chemical physics , materials science , trapping , nanocrystal , electron , luminescence , chemistry , photochemistry , optoelectronics , nanotechnology , fluorescence , condensed matter physics , optics , crystallography , physics , ecology , quantum mechanics , biology
Lead halide perovskite nanocrystals (NCs) are emerging as optically active materials for solution-processed optoelectronic devices. Despite the technological relevance of tracing rational guidelines for optimizing their performances and stability beyond their intrinsic resilience to structural imperfections, no in-depth study of the role of selective carrier trapping and environmental conditions on their exciton dynamics has been reported to date. Here we conduct spectro-electrochemical (SEC) experiments, side-by-side to oxygen sensing measurements on CsPbBr 3 NCs for the first time. We show that the application of EC potentials controls the emission intensity by altering the occupancy of defect states without degrading the NCs. Reductive potentials lead to strong (60%) emission quenching by trapping of photogenerated holes, whereas the concomitant suppression of electron trapping is nearly inconsequential to the emission efficiency. Consistently, oxidizing conditions result in minor (5%) brightening due to suppressed hole trapping, confirming that electron traps play a minor role in nonradiative decay. This behavior is rationalized through a model that links the occupancy of trap sites with the position of the NC Fermi level controlled by the EC potential. Photoluminescence measurements in controlled atmosphere reveal strong quenching by collisional interactions with O 2 , which is in contrast to the photobrightening effect observed in films and single crystals. This indicates that O 2 acts as a scavenger of photoexcited electrons without mediation by structural defects and, together with the asymmetrical SEC response, suggests that electron-rich defects are likely less abundant in nanostructured perovskites than in the bulk, leading to an emission response dominated by direct interaction with the environment.