Suppressing Halide Phase Segregation in Wide-Bandgap Perovskite for Perovskite-Organic Tandem Solar Cells
Xiao Guo a b, Zhenrong Jia a b, Zijing Dong a b, Yi Hou a b
a Department of Chemical and Biomolecular Engineering, National University of Singapore, Engineering Drive 3, 1, Singapore, Singapore
b Solar Energy Research Institute of Singapore, Singapore
Oral, Xiao Guo, presentation 021
Publication date: 17th October 2024

Iodide and bromide integration facilitate broad bandgap tunability in wide-bandgap perovskites [1], yet high concentrations of bromide incorporation lead to notorious halide phase segregation phenomenon [2], which will adversely affect the efficiency and stability of solar cell devices [3]. Herein [4], 2-amino-4,5-imidazoledicarbonitrile (AIDCN), with highly polarized charge distribution, compact molecular configuration and designed functional groups, is incorporated into a 1.86 eV wide-bandgap perovskite to effectively suppress photoinduced iodine escape and halide phase segregation by inducing specific chemical interactions with perovskite. Hyperspectral photoluminescence microscopy reveals that AIDCN mitigates halide phase segregation under continuous laser exposure. Concurrent in situ grazing-incidence wide-angle X-ray scattering and X-ray fluorescence measurements further validate suppressed iodine escape, evidenced by a notable slowing down of lattice shrinkage and a well-maintained overall chemical composition of the perovskite under continuous illumination. These findings, for the first time, provide experimental evidences that correlate the initiation of halide phase segregation to the photoinduced iodine escape process. Ultimately, by applying AIDCN, we achieve a power conversion efficiency (PCE) of 18.52% in 1.86 eV wide-bandgap perovskite solar cells with a T80 lifetime of 271 hours under continuous tracking at the maximum power point. By integrating this perovskite subcell with a PM6:BTP-eC9 organic subcell, the perovskite-organic tandem solar cell attains a maximum PCE of 25.13%, with a Japan Electrical Safety & Environment Technology Laboratories-certified stabilized PCE of 23.40% included in the “best research-cell efficiency chart” by National Renewable Energy Laboratory of US. These results underscore the efficacy of our approach in strategically designing the molecular structure of additives to induce specific chemical interactions, which not only mitigate halide phase segregation and photoinduced iodine escape but also significantly enhance the efficiency and stability of perovskite-based tandem solar cells.

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