Electron transport layer (ETL) is pivotal to charge carrier transport for PSCs to reach the Shockley–Queisser limit. This study provides a fundamental understanding of heterojunction electron transport layers (ETLs) at the atomic level for stable and efficient perovskite solar cells (PSCs). The bilayer structure of an ETL composed of SnO2 on TiO2 was examined, revealing a critical factor limiting its potential to obtain efficient performance. Alteration of oxygen vacancies in the TiO2 underlayer via an annealing process is found to induce manipulated band offsets at the interface between the TiO2 and SnO2 layers. In-depth electronic investigations of the bilayer structure elucidate the importance of the electronic properties at the interface between the TiO2 and SnO2 layers. The apparent correlation in hysteresis phenomena, including current density–voltage (J–V) curves, appears as a function of the type of band alignment. Density functional theory calculations reveal the intimate relationship between oxygen vacancies, deep trap states, and charge transport efficiency at the interface between the TiO2 and SnO2 layers. The formation of cascade band alignment via control over the TiO2 underlayer enhances device performance and suppresses hysteresis. Optimal performance exhibits a power conversion efficiency (PCE) of 23.45% with an open-circuit voltage (Voc) of 1.184 V, showing better device stability under maximum power point tracking compared with a staggered bilayer under one-sun continuous illumination.
Bibliographical noteFunding Information:
Y.K. and T.K. contributed equally to this work. This work was supported by the New & Renewable Energy Core Technology Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) granted financial resource from the Ministry of Trade, Industry & Energy (MOTIE), Republic of Korea (No. 20213091010020), National Research Foundation of Korea (NRF) grant funded by the Korea Government (MSIT) (2020R1A2C1101085) and the Korea Institute of Planning and Evaluation for Technology in Food, Agriculture and Forestry (IPET) and Korea Smart Farm R&D Foundation (KosFarm) through Smart Farm Innovation Technology Development Program, funded by the Ministry of Agriculture, Food and Rural Affairs (MAFRA) and the Ministry of Science and ICT (MSIT), Rural Development Administration (RDA) (421036‐03).
© 2022 Zhengzhou University.
- electron transport bilayer
- heterojunction bilayers
- interfacial defect
- oxygen vacancy engineering
- perovskite solar cells
ASJC Scopus subject areas
- Water Science and Technology
- Environmental Science (miscellaneous)
- Energy (miscellaneous)
- Waste Management and Disposal
- General Materials Science
- Renewable Energy, Sustainability and the Environment