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Stabilizing halide perovskite surfaces for solar cell operation with wide-bandgap lead oxysalts

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Science  02 Aug 2019:
Vol. 365, Issue 6452, pp. 473-478
DOI: 10.1126/science.aax3294

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Stability through oxysalts

The stability of organic-inorganic perovskite solar cells is limited by degradation from oxygen and water. Yang et al. show that in situ reaction of perovskites with sulfate or phosphate ions can create thin, strongly bonded lead oxysalt layers that protect defect sites. This layer also boosts charge carrier lifetimes that lead to a power conversion efficiency of more than 20%. Encapsulated devices maintained about 97% of this efficiency with simulated solar irradiation for nearly 2 months at a realistic operation temperature of 65°C.

Science, this issue p. 473

Abstract

We show that converting the surfaces of lead halide perovskite to water-insoluble lead (II) oxysalt through reaction with sulfate or phosphate ions can effectively stabilize the perovskite surface and bulk material. These capping lead oxysalt thin layers enhance the water resistance of the perovskite films by forming strong chemical bonds. The wide-bandgap lead oxysalt layers also reduce the defect density on the perovskite surfaces by passivating undercoordinated surface lead centers, which are defect-nucleating sites. Formation of the lead oxysalt layer increases the carrier recombination lifetime and boosts the efficiency of the solar cells to 21.1%. Encapsulated devices stabilized by the lead oxysalt layers maintain 96.8% of their initial efficiency after operation at maximum power point under simulated air mass (AM) 1.5 G irradiation for 1200 hours at 65°C.

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