MRS Meetings and Events

 

EL17.07.08 2023 MRS Spring Meeting

Extending the Defect Tolerance of Halide Perovskite Nanocrystals to Hot Carrier Cooling Dynamics

When and Where

Apr 13, 2023
11:45am - 12:00pm

Moscone West, Level 3, Room 3006

Presenter

Co-Author(s)

Junzhi Ye1,2,Navendu Mondal3,Ben Carwithen3,Yunwei Zhang4,Linjie Dai1,Xiangbin Fan1,Pratyush Ghosh1,Clara Otero Martinez5,Zhongzheng Yu1,Ziming Chen3,Neil Greenham1,Samuel Stranks1,Lakshminarayana Polavarapu5,Akshay Rao1,Artem Bakulin3,Robert Hoye2

University of Cambridge1,University of Oxford2,Imperial College London3,Sun Yat-sen University4,University of Vigos5

Abstract

Junzhi Ye1,2,Navendu Mondal3,Ben Carwithen3,Yunwei Zhang4,Linjie Dai1,Xiangbin Fan1,Pratyush Ghosh1,Clara Otero Martinez5,Zhongzheng Yu1,Ziming Chen3,Neil Greenham1,Samuel Stranks1,Lakshminarayana Polavarapu5,Akshay Rao1,Artem Bakulin3,Robert Hoye2

University of Cambridge1,University of Oxford2,Imperial College London3,Sun Yat-sen University4,University of Vigos5
One of the key enabling properties of low-bandgap lead-halide perovskite nanocrystals (CsPbX<sub>3</sub> NCs) for optoelectronic applications is their tolerance to point defects. Thus far, the discussion around defect tolerance has mostly focussed on recombination of charge-carriers from the band-edge. But understanding influence of these defects on hot carrier (HC) cooling will also be critical for achieving more efficient NC-based devices, but has not been thoroughly explored thus far. Here, we address this knowledge gap by elucidating the influence of intentionally-introduced traps (primarily halide vacancies) on HC relaxation above the band-edge in CsPbX<sub>3</sub> NCs with different halide compositions (CsPbBr<sub>3</sub>, CsPbBr<sub>x</sub>I<sub>3-x</sub>, and CsPbI<sub>3</sub>). The HC cooling kinetics in these different NC systems are probed by energy-dependent photoluminescence quantum yield measurements, along with pump-probe (two-pulse) and pump-push-probe (three-pulse) transient absorption measurements. We show that the presence of defect states increases the chances of HC trapping, which speeds up the cooling process. However, the change in HC cooling lifetime due to the trap densities becomes smaller as the composition moves from Br-based NCs to I-based NCs. Based on density function theory (DFT) calculation and hot carrier kinetic modelling, the cooling speed is governed by both defect densities and defect position relative to the conduction band edge. Shallower defects would allow faster trapping and de-trapping process for the carriers, which it helps to maintain the free carrier densities and allow free carriers to cool slowly with the effect of Auger reheating. This work firstly demonstrated experimental observations of the defect-tolerance nature of perovskite NCs to hot carriers, which provides insights into designing high-efficiency photovoltaic devices by managing defect densities for different bandgap perovskites.

Keywords

electron-phonon interactions | optical properties

Symposium Organizers

Himchan Cho, Korea Advanced Institute of Science and Technology
Tae-Hee Han, Hanyang University
Lina Quan, Virginia Institute of Technology
Barry Rand, Princeton University

Symposium Support

Bronze
McScience

Publishing Alliance

MRS publishes with Springer Nature