Stratified Oxygen Vacancies Enhance the Performance of Mesoporous TiO2 Electron Transport Layer in Printable Perovskite Solar Cells

Jiale Liu; Sheng Li; Zexiong Qiu; Yang Liu; Cheng Qiu; Wenhao Zhang; Jianhang Qi; Kai Chen; Wei Wang; Chaoyang Wang; Zhaozhen Cui; Yaqiong Su; Yue Hu; Anyi Mei; Hongwei Han

doi:10.1002/smll.202300737

Stratified Oxygen Vacancies Enhance the Performance of Mesoporous TiO₂ Electron Transport Layer in Printable Perovskite Solar Cells

Small. 2023 Aug;19(32):e2300737. doi: 10.1002/smll.202300737. Epub 2023 Apr 14.

Authors

Jiale Liu¹, Sheng Li¹, Zexiong Qiu¹, Yang Liu¹, Cheng Qiu¹, Wenhao Zhang¹, Jianhang Qi¹, Kai Chen¹, Wei Wang¹, Chaoyang Wang¹, Zhaozhen Cui¹, Yaqiong Su², Yue Hu¹, Anyi Mei¹, Hongwei Han¹

Affiliations

¹ Michael Grätzel Center for Mesoscopic Solar Cells, Wuhan National Laboratory for Optoelectronics, Key Laboratory of Materials Chemistry for Energy Conversion and Storage of Ministry of Education, Huazhong University of Science and Technology, Wuhan, Hubei, 430074, P. R. China.
² School of Chemistry, Xi'an Key Laboratory of Sustainable Energy Materials Chemistry, State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University, Xi'an, 710049, China.

PMID: 37060225
DOI: 10.1002/smll.202300737

Abstract

The low electrical conductivity and the high surface defect density of the TiO₂ electron transport layer (ETL) limit the power conversion efficiency (PCE) of corresponding perovskite solar cells (PSCs). Here, the conductivity and defect modulation of the mesoporous TiO₂ (mp-TiO₂ ) ETL via oxygen vacancy (OV) management by the reduction and oxidation treatment are reported. Reduction treatment via reducing agent introduces abundant OVs into the TiO₂ nanocrystalline particles on the surface and at the subsurface. The following oxidation treatment via hydrogen peroxide removes the surface OVs while remains the subsurface OVs, resulting in stratified OVs. The stratified OVs improve the conductivity of TiO₂ ETL by increasing carrier donors and decrease nonradiative centers by reducing surface defects. Such synergy ensures the capability of mp-TiO₂ as the well-performed ETL with improved energy level alignment, suppressed interface recombination, enhanced carrier extraction, and transport. As a result, printable hole-conductor-free carbon-based mesoscopic PSCs based on the modulated mp-TiO₂ ETL demonstrate a highest reported PCE of 18.96%.

Keywords: oxygen vacancy; perovskite solar cells; printable; stratified; titanium dioxide.

Abstract

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