Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 114, Issue 29, Pages 7519-7524Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1704421114
Keywords
organic-inorganic hybrid perovskite; carrier lifetime; photoluminescence; polaron
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Funding
- US Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences [DE-SC0016144]
- Ministry of Science and Technology of Taiwan (MOST) [105-2119-M-002-046-MY3]
- Office of Science of the US DOE [DE-AC02-05CH11231]
- NIH/National Institute of General Medical Sciences via NSF [DMR-1332208]
- NSF
- U.S. Department of Energy (DOE) [DE-SC0016144] Funding Source: U.S. Department of Energy (DOE)
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Long carrier lifetime is what makes hybrid organic-inorganic perovskites high-performance photovoltaic materials. Several microscopic mechanisms behind the unusually long carrier lifetime have been proposed, such as formation of large polarons, Rashba effect, ferroelectric domains, and photon recycling. Here, we show that the screening of band-edge charge carriers by rotation of organic cation molecules can be a major contribution to the prolonged carrier lifetime. Our results reveal that the band-edge carrier lifetime increases when the system enters from a phase with lower rotational entropy to another phase with higher entropy. These results imply that the recombination of the photoexcited electrons and holes is suppressed by the screening, leading to the formation of polarons and thereby extending the lifetime. Thus, searching for organic-inorganic perovskites with high rotational entropy over a wide range of temperature may be a key to achieve superior solar cell performance.
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