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Low-Temperature Synthesized Nb-Doped TiO2 Electron Transport Layer Enabling High-Efficiency Perovskite Solar Cells by Band Alignment Tuning
journal contribution
posted on 2020-03-19, 21:03 authored by Yoshitaka Sanehira, Naoyuki Shibayama, Youhei Numata, Masashi Ikegami, Tsutomu MiyasakaAn Nb-doped TiO2 (Nb-TiO2) film comprising a double structure stacked
with a bottom compact layer and top mesoporous layers was synthesized
by treating a Ti precursor-coated substrate using a one-step low-temperature
steam-annealing (SA) method. The SA-based Nb-TiO2 films
possess high crystallinity and conductivity, and that allows better
control over the conduction band (CB) of TiO2 for the electron
transport layer (ETL) of the perovskite solar cells by the Nb doping
level. Optimization of power conversion efficiency (PCE) for the Nb-TiO2-based ETL was combined with the CB level tuning of the mixed-halide
perovskite by changing the Br/I ratio. This band offset management
enabled to establish the most suitable energy levels between the ETL
and the perovskites. This method was applied to reduce the band gap
of perovskites to enhance the photocurrent density while maintaining
a high open-circuit voltage. As a result, the optimal combination
of 5 mol % Nb-TiO2 ETL and 10 mol % Br in the mixed-halide
perovskite exhibited high photovoltaic performance for low-temperature
device fabrication, achieving a high-yield PCE of 21.3%.
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Nb doping levelelectron transport layermolpower conversion efficiencyNb-doped TiO 2methodBand Alignment TuningETLBrCBSA-based Nb-TiO 2 filmsmixed-halide perovskiteTi precursor-coated substrateLow-Temperature Synthesized Nb-Doped TiO 2 Electron Transport Layer Enabling High-Efficiency Perovskite Solar CellsPCENb-TiO 2
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