Enhanced Electron Extraction in Co-Doped TiO 2 Quantified by Drift-Diffusion Simulation for Stable CsPbI 3 Solar Cells
Résumé
Solar cells based on inorganic perovskite CsPbI 3 are promising candidates to resolve the challenge of operational stability in the field of perovskite photovoltaics. For stable operation, however, it is crucial to thoroughly understand the extractive and recombinative processes occurring at the interfaces of perovskite and the chargeselective layers. In this study, we focus on the electronic properties of (doped) TiO 2 as an electron-selective contact. We show via KPFM that co-doping of TiO 2 with Nb(V) and Sn(IV) reduces the material's work function by 270 meV, giving it stronger n-type characteristics compared to Nb(V) mono-doped TiO 2 . The modified electronic alignment with CsPbI 3 translates to enhanced electron extraction, as demonstrated with steady-state photoluminescence spectroscopy, transient photoluminescence and transient surface photovoltage in triad. Importantly, we extract crucial parameters, such as the concentration of extracted electrons and the interface hole recombination velocity, from the SPV transients via 2D drift-diffusion simulations. When implementing the co-doped TiO 2 into full n-i-p solar cells, the operational stability under continuous AM1.5G illumination is enhanced from 970 h to 25'000 h of projected T S80 lifetime. This study provides fundamental understanding of interfacial charge extraction and its correlation with operational stability of perovskite solar cells, which can be transferred to other charge-selective contacts.
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