Selective contact, bandgap and passivation engineering in vacuum deposited perovskites for tandem solar cells
Yu-Hsien Chiang a, Miguel Anaya a, Kyle Frohna a, Hayden Salway a, Sam Stranks a b
a Department of Physics, Cavendish Laboratory, University of Cambridge; Cambridge, UK
b Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, Cambridge CB3 0AS, UK
International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV22)
València, Spain, 2022 May 19th - 25th
Organizers: Pablo Docampo, Eva Unger and Elizabeth Gibson
Oral, Yu-Hsien Chiang, presentation 096
Publication date: 20th April 2022

In this study, we demonstrate how the bandgap of an evaporated perovskite film can be tuned from 1.62 eV to 1.8 eV by multisource thermal evaporation. With an optimised contact layer studies, the device PCE can achieve 20.7% for a bandgap of 1.62 eV showing highest PCE in multisource evaporation system. We futher perfrom the comprehensive structural and photophysics characterization to understand the bandgap variation and identify a bandgap threshold at 1.8 eV leading to the phase segregation. This promising result reflect in the device open-circuit voltage (VOC) where we reveal the linear VOC increment with higher bandgap. With futher surface passivation of Ethyldiammouiunm diiodide (EDAI) treatment, the photoluminescence quantum efficiency can be enhanced by one order magnitude and the device VOC achieves 1.26 V with the bandgap of 1.76 eV, which is by far the less Voc loss among the p-i-n perovskite solar cells with MA-free composition. Using the same passition method, EDAI also enhances the quality of MA-free Pb-Sn perovskite solar cells, leading to a VOC of 0.86 V with the bandgap of 1.28 eV. With these results, we reveal a 2-terminal all-perovskite tandem solar cells with a 24.1% PCE by a MA-free perovskite composition. This result shows the promising of evaporation technique for all-perovskite tandem solar cell and encourages the community to expore more possibility. 

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