Journal
ADVANCED ENERGY MATERIALS
Volume 10, Issue 9, Pages -Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/aenm.201903488
Keywords
electric fields; halide segregation; perovskites; photovoltaic devices; trap states
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Funding
- Engineering and Physical Sciences Research Council (U.K.) (EPSRC)
- University College Oxford from the Oxford-Radcliffe endowment
- Alexander-vonHumboldt Foundation
- EPSRC [EP/M024881/1, EP/P033229/1, EP/S004947/1] Funding Source: UKRI
- Engineering and Physical Sciences Research Council [EP/M024881/1, 1804061, EP/S004947/1] Funding Source: researchfish
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Mixed-halide perovskites are essential for use in all-perovskite or perovskite-silicon tandem solar cells due to their tunable bandgap. However, trap states and halide segregation currently present the two main challenges for efficient mixed-halide perovskite technologies. Here photoluminescence techniques are used to study trap states and halide segregation in full mixed-halide perovskite photovoltaic devices. This work identifies three distinct defect species in the perovskite material: a charged, mobile defect that traps charge-carriers in the perovskite, a charge-neutral defect that induces halide segregation, and a charged, mobile defect that screens the perovskite from external electric fields. These three defects are proposed to be MA(+) interstitials, crystal distortions, and halide vacancies and/or interstitials, respectively. Finally, external quantum efficiency measurements show that photoexcited charge-carriers can be extracted from the iodide-rich low-bandgap regions of the phase-segregated perovskite formed under illumination, suggesting the existence of charge-carrier percolation pathways through grain boundaries where phase-segregation may occur.
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