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Performance-limiting nanoscale trap clusters at grain junctions in halide perovskites

DOI: 10.1038/s41586-020-2184-1 DOI Help

Authors: Tiarnan A. S. Doherty (University of Cambridge) , Andrew J. Winchester (Okinawa Institute of Science and Technology Graduate University) , Stuart Macpherson (University of Cambridge) , Duncan N. Johnstone (University of Cambridge) , Vivek Pareek (Okinawa Institute of Science and Technology Graduate University) , Elizabeth M. Tennyson (University of Cambridge) , Sofiia Kosar (Okinawa Institute of Science and Technology Graduate University) , Felix U. Kosasih (University of Cambridge) , Miguel Anaya (University of Cambridge) , Mojtaba Abdi-jalebi (University of Cambridge) , Zahra Andaji-garmaroudi (University of Cambridge) , E. Laine Wong (Okinawa Institute of Science and Technology Graduate University,) , Julien Madéo (Okinawa Institute of Science and Technology Graduate University) , Yu-hsien Chiang (University of Cambridge) , Ji-sang Park (Kyungpook National University) , Young-kwang Jung (Yonsei University) , Christopher E. Petoukhoff (Okinawa Institute of Science and Technology Graduate University) , Giorgio Divitini (University of Cambridge) , Michael K. l. Man (Okinawa Institute of Science and Technology Graduate University) , Caterina Ducati (University of Cambridge) , Aron Walsh (Imperial College London) , Paul A. Midgley (University of Cambridge) , Keshav M. Dani (Okinawa Institute of Science and Technology Graduate University) , Samuel D. Stranks (University of Cambridge)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Nature , VOL 580 , PAGES 360 - 366

State: Published (Approved)
Published: April 2020
Diamond Proposal Number(s): 19023 , 19793

Abstract: Halide perovskite materials have promising performance characteristics for low-cost optoelectronic applications. Photovoltaic devices fabricated from perovskite absorbers have reached power conversion efficiencies above 25 per cent in single-junction devices and 28 per cent in tandem devices. This strong performance (albeit below the practical limits of about 30 per cent and 35 per cent, respectively) is surprising in thin films processed from solution at low-temperature, a method that generally produces abundant crystalline defects. Although point defects often induce only shallow electronic states in the perovskite bandgap that do not affect performance, perovskite devices still have many states deep within the bandgap that trap charge carriers and cause them to recombine non-radiatively. These deep trap states thus induce local variations in photoluminescence and limit the device performance. The origin and distribution of these trap states are unknown, but they have been associated with light-induced halide segregation in mixed-halide perovskite compositions and with local strain, both of which make devices less stable. Here we use photoemission electron microscopy to image the trap distribution in state-of-the-art halide perovskite films. Instead of a relatively uniform distribution within regions of poor photoluminescence efficiency, we observe discrete, nanoscale trap clusters. By correlating microscopy measurements with scanning electron analytical techniques, we find that these trap clusters appear at the interfaces between crystallographically and compositionally distinct entities. Finally, by generating time-resolved photoemission sequences of the photo-excited carrier trapping process, we reveal a hole-trapping character with the kinetics limited by diffusion of holes to the local trap clusters. Our approach shows that managing structure and composition on the nanoscale will be essential for optimal performance of halide perovskite devices.

Subject Areas: Materials, Energy

Diamond Offline Facilities: Electron Physical Sciences Imaging Centre (ePSIC)
Instruments: E02-JEM ARM 300CF , I14-Hard X-ray Nanoprobe