BEGIN:VCALENDAR VERSION:2.0 PRODID:Data::ICal 0.22 BEGIN:VEVENT DESCRIPTION:Tianran Chen\, UVA-Physics\n\n
Long carrier lifetime is what makes hybrid org anic-inorganic perovskites high performance photovoltaic materials. Severa l microscopic mechanisms behind the unusually long carrier lifetime have b een proposed\, such as formation of large polarons\, Rashba effect\, ferro electric 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 rev eal that the band-edge carrier lifetime increases when the system enters f rom a phase with lower rotational entropy to another phase with higher ent ropy. These results imply that the recombination of the photo-excited elec trons and holes is suppressed by the screening\, leading to the formation of polarons and thereby extending the lifetime. Thus\, searching for organ ic-inorganic perovskites with high rotational entropy over a wide range of temperature may be a key to achieve superior solar cell performance.
\n DTSTART:20170908T193000Z LOCATION:Physics Building\, Room 204 SUMMARY:Origin of Long Lifetime of Band-Edge Charge Carriers in Organic-Ino rganic Lead Iodide Perovskites END:VEVENT END:VCALENDAR