SnO2 with its excellent properties such as high optical transparency, suitable band energy and high electron mobility, recently has received special attention from researchers as an outstanding electron transport layer (ETL) for optoelectronic devices. Here, we demonstrate that SnO2 combined with ionic liquid (IL), 1-benzyl-3-methylimidazolium chloride ([BzMIM]Cl), based on low-temperature solution-processed can be an excellent ETL for efficient inverted organic solar cells (iOSCs). Our best performance with P3HT:PC60BM based iOSCs using SnO2/IL as an ETL, has achieved a power conversion efficiency (PCE) of 4.05%, which is the highest reported value so far and was a 38% increase compared to that of SnO2 only (2.94%). Using ultraviolet photoelectron spectroscopy, we found that the work function of the cathode decreased significantly from − 4.38 eV to − 3.82 eV for SnO2/IL, an outstanding feature that is necessary for an ideal ETL. Electrochemical impedance spectroscopy studies revealed a significant lower transport resistance and an efficient charge extraction at the interface between photoactive layer and the electrode for the SnO2/IL-based iOSC than for the SnO2 only device. The iOSC devices using SnO2/IL showed excellent long-term stability, with a PCE of ~ 81% compared to the initial value after storage for 2.5 months in ambient conditions. This low-temperature solution-processed SnO2/IL is expected for low-cost, high throughput, roll-to-roll process on flexible substrates for iOSC as well as other optoelectronic devices.
Bibliographical noteFunding Information:
This research was supported by the Pioneer Research Center Program through the National Research Foundation of Korea funded by the Ministry of Science, ICT & Future Planning ( NRF-2013M3C1A3065528 ). This research also was supported by National Research Foundation of Korea (NRF) funded by Ministry of Science, ICT & Future Planning ( 2017R1A2B3006141 ).
© 2017 Elsevier B.V.
Copyright 2018 Elsevier B.V., All rights reserved.
- Electron transport layer
- Inverted organic solar cells
- Ionic liquid
- Solution-processed metal oxides
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Surfaces, Coatings and Films