Nanoscale Chemical Landscape Dominates Optoelectronic Response in Alloyed Halide Perovskites
Kyle Frohna a, Miguel Anaya a b, Stuart Macpherson a, Jooyoung Sung a, Tiarnan A.S. Doherty a b, Yu-Hsien Chiang a, Andrew J. Winchester c, Kieran W.P. Orr a b, Julia E. Parker d, Paul D. Quinn d, Keshav M. Dani c, Akshay Rao a, Samuel D. Stranks a b
a Cavendish Laboratory, University of Cambridge, Cambridge, UK
b Department of Chemical Engineering and Biotechnology, University of Cambridge; Cambridge, UK
c Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa, 904 0495, Japan
d Diamond Light Source, Didcot OX11 0DE, UK.
International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV22)
València, Spain, 2022 May 19th - 25th
Organizers: Pablo Docampo, Eva Unger and Elizabeth Gibson
Oral, Kyle Frohna, presentation 081
Publication date: 20th April 2022

Halide perovskites perform remarkably in optoelectronic devices including tandem photovoltaics1,2. However, this exceptional performance is striking given that perovskites exhibit deep charge carrier traps and spatial compositional and structural heterogeneity3-5, all of which would be expected to negatively impact performance. In this presentation, I will discuss how we resolve this long-standing paradox by providing a global visualisation of the nanoscale chemical, structural and optoelectronic landscape in halide perovskite devices6. The development of a new suite of correlative, multimodal microscopy measurements combining quantitative optical spectroscopic techniques and synchrotron nanoprobe measurements which enabled us to understand this complex landscape will be described. I will show that compositional disorder dominates the optoelectronic response, while nanoscale strain variations, even of large magnitude (~1 %) which would be deleterious to performance in III-V devices7, have only a weak influence. Nanoscale compositional gradients drive carrier funneling onto local regions associated with low electronic disorder. These energetic funnels draw carrier recombination away from trap clusters associated with high electronic disorder and leading to high local photoluminescence quantum efficiency. These measurements reveal a global picture of the competitive nanoscale landscape, which endows enhanced defect tolerance in devices through spatial chemical disorder that outcompetes both electronic and structural disorder.

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