TY - JOUR
T1 - Performance-limiting nanoscale trap clusters at grain junctions in halide perovskites
AU - Doherty, Tiarnan A.S.
AU - Winchester, Andrew J.
AU - Macpherson, Stuart
AU - Johnstone, Duncan N.
AU - Pareek, Vivek
AU - Tennyson, Elizabeth M.
AU - Kosar, Sofiia
AU - Kosasih, Felix U.
AU - Anaya, Miguel
AU - Abdi-Jalebi, Mojtaba
AU - Andaji-Garmaroudi, Zahra
AU - Wong, E. Laine
AU - Madéo, Julien
AU - Chiang, Yu Hsien
AU - Park, Ji Sang
AU - Jung, Young Kwang
AU - Petoukhoff, Christopher E.
AU - Divitini, Giorgio
AU - Man, Michael K. L
AU - Ducati, Caterina
AU - Walsh, Aron
AU - Midgley, Paul A.
AU - Dani, Keshav M.
AU - Stranks, Samuel D.
N1 - Publisher Copyright:
© 2020, The Author(s), under exclusive licence to Springer Nature Limited.
PY - 2020/4/16
Y1 - 2020/4/16
N2 - 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 devices1,2. This strong performance (albeit below the practical limits of about 30 per cent and 35 per cent, respectively3) is surprising in thin films processed from solution at low-temperature, a method that generally produces abundant crystalline defects4. Although point defects often induce only shallow electronic states in the perovskite bandgap that do not affect performance5, 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 performance6. The origin and distribution of these trap states are unknown, but they have been associated with light-induced halide segregation in mixed-halide perovskite compositions7 and with local strain8, both of which make devices less stable9. 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 process10,11, 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.
AB - 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 devices1,2. This strong performance (albeit below the practical limits of about 30 per cent and 35 per cent, respectively3) is surprising in thin films processed from solution at low-temperature, a method that generally produces abundant crystalline defects4. Although point defects often induce only shallow electronic states in the perovskite bandgap that do not affect performance5, 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 performance6. The origin and distribution of these trap states are unknown, but they have been associated with light-induced halide segregation in mixed-halide perovskite compositions7 and with local strain8, both of which make devices less stable9. 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 process10,11, 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.
UR - http://www.scopus.com/inward/record.url?scp=85083677084&partnerID=8YFLogxK
U2 - 10.1038/s41586-020-2184-1
DO - 10.1038/s41586-020-2184-1
M3 - Article
C2 - 32296189
AN - SCOPUS:85083677084
SN - 0028-0836
VL - 580
SP - 360
EP - 366
JO - Nature
JF - Nature
IS - 7803
ER -