Alumina Nanoparticle Interfacial Buffer Layer for Low-Bandgap Lead-Tin Perovskite Solar Cells |
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Authors: | Heon Jin Michael D Farrar James M Ball Akash Dasgupta Pietro Caprioglio Sudarshan Narayanan Robert D J Oliver Florine M Rombach Benjamin W J Putland Michael B Johnston Henry J Snaith |
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Affiliation: | 1. Department of Physics, University of Oxford, Clarendon Laboratory, Oxford, OX1 3PU UK;2. Department of Materials, University of Oxford, Oxford, OX1 3PH UK |
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Abstract: | Mixed lead-tin (Pb:Sn) halide perovskites are promising absorbers with narrow-bandgaps (1.25–1.4 eV) suitable for high-efficiency all-perovskite tandem solar cells. However, solution processing of optimally thick Pb:Sn perovskite films is notoriously difficult in comparison with their neat-Pb counterparts. This is partly due to the rapid crystallization of Sn-based perovskites, resulting in films that have a high degree of roughness. Rougher films are harder to coat conformally with subsequent layers using solution-based processing techniques leading to contact between the absorber and the top metal electrode in completed devices, resulting in a loss of VOC, fill factor, efficiency, and stability. Herein, this study employs a non-continuous layer of alumina nanoparticles distributed on the surface of rough Pb:Sn perovskite films. Using this approach, the conformality of the subsequent electron-transport layer, which is only tens of nanometres in thickness is improved. The overall maximum-power-point-tracked efficiency improves by 65% and the steady-state VOC improves by 28%. Application of the alumina nanoparticles as an interfacial buffer layer also results in highly reproducible Pb:Sn solar cell devices while simultaneously improving device stability at 65 °C under full spectrum simulated solar irradiance. Aged devices show a six-fold improvement in stability over pristine Pb:Sn devices, increasing their lifetime to 120 h. |
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Keywords: | lead-tin low-bandgap methylammonium-free perovskites shunt management |
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