Enhanced Efficiency and Stability of Perovskite Solar Cells Enabled by Alkaline-Earth Bis(trifluoromethanesulfonimide) Additives Engineering
Ngoc Duy Pham a, Hongxia Wang a
a School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology (QUT), Australia, George Street, 2, Brisbane City, Australia
Proceedings of International Conference on Advanced Light Absorbing Materials for Next Generation Photovoltaics (ABSOGEN)
Online, Spain, 2020 November 17th - 18th
Organizers: Hongxia Wang, Xiaojing Hao and Lydia Wong
Oral, Ngoc Duy Pham, presentation 016
Publication date: 6th November 2020

Environmental stability remains one of the greatest barriers to the commercialization of perovskite solar cells (PSCs). The presence of Li-TFSI – a prerequisite dopant for the hole conductor-based Spiro-OMeTAD has been linked to the stability of perovskite devices, e.g., the rapid aggregation and hydration of Li-TFSI upon moisture exposure has been shown to play a key role in the degradation of PSCs.1, 2 Here we show that this issue can be tackled by replacing the Li-TFSI with the more hydrophobic alkaline-earth bis(trifluoromethanesulfonyl)imide additives (AEBAs), namely Mg-TFSI2 and Ca-TFSI2 owing to the formation of more robust coordination complexes between the TFSI-salts and 4-tert-Butylpyridine. Intriguingly, the presence of AEBAs also improve hole mobilities in Spiro-OMeTAD and energy alignment with adjacent perovskite layer, which ultimately contribute to the favourable carrier extraction at the perovskite/Spiro-OMeTAD interface. Consequently, our PSCs stabilized by the AEBAs yield a champion efficiency of 20.04%, increased from 18.08% for PSCs made with Li-TFSI, while device stability is significantly enhanced.3

The research leading to these results was financially supported by Australian Research Council Discovery Project (DP190102252). Ngoc Duy Pham and Hongxia Wang thank the support of Centre for Material Science, Queensland University of Technology (QUT). The data of SEM, TEM, XPS, UPS, AFM and XRD reported in this article were obtained at the Central Analytical Research facility (CARF), QUT. Access to CARF was supported by the generous funding from Science and Engineering faculty, QUT.

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