Journal
ADVANCED MATERIALS INTERFACES
Volume 5, Issue 15, Pages -Publisher
WILEY
DOI: 10.1002/admi.201800464
Keywords
defect recombination; double perovskite; lifetime; time-resolved photoluminescence; transient absorption spectroscopy
Funding
- Magdalene College, Cambridge
- EPSRC Cambridge NanoDTC [EP/L015978/1]
- EPSRC [EP/L000202/1, EP/M005143/1, EP/L0011700/1]
- Indo-UK APEX project
- UKIERI
- Isaac Newton Trust [Minute 13.38(k)]
- Winton Trust
- Herchel Smith Postdoctoral Fellowship at the University of Cambridge
- Winton Programme for the Physics of Sustainability
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There is current interest in finding nontoxic alternatives to lead-halide perovskites for optoelectronic applications. Silver-bismuth double perovskites have recently gained attention, but evaluating their carrier lifetime and recombination mechanisms from photoluminescence measurements is challenging due to their indirect bandgap. In this work, transient absorption spectroscopy is used to directly track the photocarrier population in Cs2AgBiBr6 by measuring the ground state bleach dynamics. A small initial drop is resolved in the ground state bleach on a picosecond timescale, after which the remaining photocarriers decay monoexponentially with a lifetime of 1.4 mu s. The majority of the early-time decay is attributed to hot-carrier thermalization from the direct transition to the indirect bandgap, and the 1.4 mu s lifetime represents the recombination of most photocarriers. From this lifetime, a steady-state excess carrier density of 2.2 x 10(16) cm(-3) under 1 sun is calculated, which is an order of magnitude larger than that for methylammonium lead iodide, suggesting that charge transport and extraction can be efficient in Cs2AgBiBr6 solar cells.
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