How Benign Are Defects in Perovskites? A Hot Carriers’ Unexpected Journey
Marcello Righetto a, Swee Sien Lim a, David Giovanni a, Melvin Jia Wei Lim a, Qiannan Zhang a, Sankaran Ramesh a, Yong Kang Eugene Tay a, Tze Chien Sum a
a NTU Singapore - Nanyang Technological University, Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Link, 21, Singapore, Singapore
International Conference on Hybrid and Organic Photovoltaics
Proceedings of Online International Conference on Hybrid and Organic Photovoltaics (OnlineHOPV20)
Online, Spain, 2020 May 26th - 29th
Organizers: Tracey Clarke, James Durrant, Annamaria Petrozza and Trystan Watson
Poster, Marcello Righetto, 120
Publication date: 22nd May 2020
ePoster: 

Amongst the many spectacular properties of hybrid lead halide perovskites, their defect tolerance is regarded as the key enabler for a spectrum of high- performance optoelectronic devices that propelled perovskites to prominence. However, the plateauing efficiency enhancements of perovskite devices calls into question the extent of this defect tolerance in perovskite systems; an opportunity for perovskite nanocrystals to fill. Through optical spectroscopy and phenomenological modeling based on the Marcus theory of charge transfer, we uncover the detrimental effect of hot carriers trapping in methylammonium lead iodide and bromide nanocrystals. Higher excess energies induce faster carrier trapping rates, ascribed to interactions with shallow traps and ligands, turning these into potent defects. Passivating these traps with the introduction of phosphine oxide ligands can help mitigate hot carrier trapping. Importantly, our findings extend beyond photovoltaics and are relevant for low threshold lasers, light-emitting devices and multi-exciton generation devices.

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