Charge Injection from Excited Cs2AgBiBr6 Quantum Dots into Semiconductor Oxides
Junsang Cho a, Jeffrey DuBose a, Prashant Kamat a
a Radiation Laboratory, University of Notre Dame
Proceedings of Internet Conference for Quantum Dots (iCQD)
Online, Spain, 2020 July 14th - 17th
Organizers: Quinten Akkerman, Raffaella Buonsanti, Zeger Hens and Maksym Kovalenko
Poster, Junsang Cho, 080
Publication date: 3rd July 2020
ePoster: 

Lead-free double perovskites such as Cs2AgBiBr6 are gaining attention because of their environmental friendliness compared to the lead halide perovskites. In order to establish their photoactivity, we have probed the excited-state behavior of Cs2AgBiBr6 nanocrystals and charge injection from their excited state into different metal oxides (TiO2, ZnO). The electron-transfer rate constants determined from ultrafast transient absorption spectroscopy were in the range of 1.2–5.2 × 1010 s–1. Under steady-state photolysis (ambient conditions), the electrons injected into TiO2 are scavenged by atmospheric oxygen, leaving behind holes which accumulate within the quantum dots (QDs). These accumulated holes further induce oxidation of QDs, resulting in the overall photodegradation of perovskite films. Annealed films of Cs2AgBiBr6 nanocrystals, when employed as an active layer in solar cells, delivered photocurrent under visible-light excitation.

The research described herein is supported by the Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences of the U.S. Department of Energy, through award DE-FC02-04ER15533. We would like to thank  Rebecca A. Scheidt for discussion of interfacial charge-transfer kinetics. This is contribution number NDRL no. 5260 from the Notre Dame Radiation Laboratory.

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