Orders of Recombination in Complete Perovskite Solar Cells – Linking Time‐Resolved and Steady‐State Measurements

Christian M Wolff,Felix Deschler,Le Quang Phuong,Jose Antonio Marquez,Sean A Bourelle,Sascha Feldmann,Thomas Unold,Jakob Wolansky,Jona Kurpiers,Pietro Caprioglio,Martin Stolterfoht,Dieter Neher,Safa Shoaee

doi:10.1002/aenm.202101823

Abstract

AbstractIdeally, the charge carrier lifetime in a solar cell is limited by the radiative free carrier recombination in the absorber which is a second‐order process. Yet, real‐life cells suffer from severe nonradiative recombination in the bulk of the absorber, at interfaces, or within other functional layers. Here, the dynamics of photogenerated charge carriers are probed directly in pin‐type mixed halide perovskite solar cells with an efficiency >20%, using time‐resolved optical absorption spectroscopy and optoelectronic techniques. The charge carrier dynamics in complete devices is fully consistent with a superposition of first‐, second‐, and third‐order recombination processes, with no admixture of recombination pathways with non‐integer order. Under solar illumination, recombination in the studied solar cells proceeds predominantly through nonradiative first‐order recombination with a lifetime of 250 ns, which competes with second‐order free charge recombination which is mostly if not entirely radiative. Results from the transient experiments are further employed to successfully explain the steady‐state solar cell properties over a wide range of illumination intensities. It is concluded that improving carrier lifetimes to >3 µs will take perovskite devices into the radiative regime, where their performance will benefit from photon‐recycling.

Highlights

Lead halide perovskites and optoelectronic devices[1] made thereof have attracted enormous attention due to a rapid rise in efficiency, the versatility of applications, and ease of processing
We find that the entire set of data can be well fitted by a superposition of first, second, and third-order recombination processes according to Equation (1a)
We show that the charge carrier recombination dynamics in efficient p-i-n-type perovskite solar cells can be described as a superposition of first, second, and thirdorder recombination, without the necessity to introduce a non-integer recombination order

Summary

Introduction

Lead halide perovskites and optoelectronic devices[1] made thereof have attracted enormous attention due to a rapid rise in efficiency, the versatility of applications, and ease of processing. The performance of perovskite-based optoelectronic devices is limited by nonradiative decay processes which compete with radiative free carrier recombination. Detailed insights into the device operation and a detailed understanding of all recombination processes are imperative for further efficiency gains. [+]Present address: École polytechnique fédérale de Lausanne STI IEM, Rue de la Maladière 71b, Neuchâtel 2000, Switzerland [++]Present address: Department of Physics, University of Oxford, Oxford, UK [+++]Present address: Walter Schottky Institut, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany. Shoaee Optoelectronics of Disordered Semiconductors Institute of Physics and Astronomy University of Potsdam Karl-Liebknecht-Str. 24-25, 14776 Potsdam, Germany

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