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Westbrook RJE, Xu W, Liang X, Webb T, Clarke TM, Haque SA. 2D Phase Purity Determines Charge-Transfer Yield at 3D/2D Lead Halide Perovskite Heterojunctions. J Phys Chem Lett 2021; 12:3312-3320. [PMID: 33769059 DOI: 10.1021/acs.jpclett.1c00362] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Targeted functionalization of 3D perovskite with a 2D passivation layer via R-NH3I treatment has emerged as an effective strategy for enhancing both the efficiency and chemical stability of ABX3 perovskite solar cells, but the underlying mechanisms behind these improvements remain unclear. Here, we assign a passivation mechanism where R-NH3I reacts with excess PbI2 in the MAPbI3 film and unsaturated PbI6 octahedra to form (R-NH3)2(MA)n-1PbnI3n+1. Crucially, we show that precise control of the 2D (R-NH3)2(MA)n-1PbnI3n+1 layer underpins performance improvements: n = 1 yields over a 2-fold improvement in hole injection to the HTL; n > 1 deteriorates hole injection. Ultrafast transient absorption spectroscopy suggests this n-dependence is rooted in the fact that fast (<6 ns) hole injection does not occur between the 3D and 2D layers. These results help explain contemporary empirical findings in the field and set out an important design rule for the further optimization of multidimensional perovskite optoelectronics.
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Affiliation(s)
- Robert J E Westbrook
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub White City Campus, Wood Lane, London W12 0BZ, U.K
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K
- Centre for Processable Electronics, Imperial College London, London SW7 2AZ, U.K
| | - Weidong Xu
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub White City Campus, Wood Lane, London W12 0BZ, U.K
- Centre for Processable Electronics, Imperial College London, London SW7 2AZ, U.K
| | - Xinxing Liang
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub White City Campus, Wood Lane, London W12 0BZ, U.K
- Centre for Processable Electronics, Imperial College London, London SW7 2AZ, U.K
| | - Thomas Webb
- Advanced Technology Institute, Department of Electrical and Electronic Engineering, University of Surrey, Guildford, Surrey GU2 7XH, U.K
| | - Tracey M Clarke
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K
| | - Saif A Haque
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub White City Campus, Wood Lane, London W12 0BZ, U.K
- Centre for Processable Electronics, Imperial College London, London SW7 2AZ, U.K
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