Journal
NATURE ENERGY
Volume 6, Issue 6, Pages 633-641Publisher
NATURE PORTFOLIO
DOI: 10.1038/s41560-021-00831-8
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Funding
- University of North Carolina at Chapel Hill
- Office of Naval Research [N68335-20-C-0390]
- National Science Foundation [ECCS-1542015]
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The addition of excessive AX in formamidinium-caesium mixed-cation perovskites improves their photostability by compensating iodide vacancies and suppressing ion migration and defects generation during long-term illumination. This approach impedes the generation of hole traps and phase segregation, ultimately enhancing the stability and efficiency of the perovskite mini-modules.
Formamidinium-caesium mixed-cation perovskites have shown better thermal stability than their methylammonium-containing counterparts but they suffer from photoinstability induced by iodide migration and phase segregation. Here we improve their photostability by adding slightly excessive AX (at a molar percentage of 0.25% to Pb2+ ions), where A is formamidinium or caesium and X is iodine. The excessive AX does not improve the initial solar cell efficiency. It compensates iodide vacancies and suppresses ion migration and defects generation during long-term illumination by around tenfold compared with AX-deficient devices. Consequently, generation of hole traps and phase segregation is impeded, with the former limiting solar cell efficiency after degradation. The perovskite mini-modules reached a certified stabilized efficiency of 18.6% with an aperture area of similar to 30 cm(2), corresponding to an active area efficiency of 20.2%. The mini-module maintains 93.6% of the initial efficiency after continuous operation under 1 sun illumination for >1,000 h at 50 +/- 5 degrees C in air.
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