Ternary organic solar cells based on ZnO-Ge double electron transport layer with enhanced power conversion efficiency

• Published in: Solar energy 2017-10, Vol.155, p.1052-1058
• Main Authors: Li, Chang, Sun, Xiaoxiang, Ni, Jian, Huang, Like, Xu, Rui, Li, Zhenglong, Cai, Hongkun, Li, Juan, Zhang, Yaofang, Zhang, Jianjun
• Format: Article
• Language: English
• Subjects: Alignment; Charge transfer; Electric contacts; Electrical properties; Electron transport; Electron transport layer; Electrons; Energy conversion efficiency; Energy efficiency; Energy levels; Feasibility studies; Inverted structure; Light penetration; Optical properties; Photovoltaic cells; Solar cells; Solar energy; Studies; Ternary organic solar cells; Zinc oxide; ZnO-Ge bilayer
• ISSN: 0038-092X; 1471-1257
• DOI: 10.1016/j.solener.2017.07.053

In this article, we first report the inverted ternary OSCs based on ZnO-Ge double ETL. By introducing the additional Ge layer, the device performance was significantly increased to 9.15%, which exhibited a 18.4% improvement compared to that of the device using ZnO-only ETL. [Display omitted] •ZnO-Ge bilayer was employed as ETL in inverted ternary organic solar cells.•Improved energy level alignment and interfacial contact between the active layer and ETL.•Enhanced optical transmittance and perpendicular electrical transport properties.•Facilitated charge transfer from the active layer to ETL.•This results in an increased PCE from 7.73% to 9.15%. A ZnO-Ge bilayer was proposed as an electron transport layer (ETL) in inverted ternary organic solar cells (OSCs). The energy level alignment, surface morphology, optical and electrical properties, and interface charge transfer were investigated to understand the impact of the additional Ge NPs layer. The results indicated that apart from improving the energy level alignment, the Ge NPs layer optimizes the interfacial contact between the active layer and ETL. Moreover, the ZnO-Ge bilayer shows better optical transmittance and perpendicular electrical transport properties compared to that of ZnO NPs layer. Benefit from the enhanced charge transfer from the active layer to ETL, the champion power conversion efficiency (PCE) was significantly increased to 9.15% by introducing the additional Ge layer, which exhibited a 18.4% improvement compared to that of the ZnO-only devices. Our results demonstrated the feasibility of ZnO-Ge bilayer as the ETL for high-performance OSCs.