An Open-Circuit Voltage and Power Conversion Efficiency Study of Fullerene Ternary Organic Solar Cells Based on Oligomer/Oligomer and Oligomer/Polymer

5 years ago

An Open-Circuit Voltage and Power Conversion Efficiency Study of Fullerene Ternary Organic Solar Cells Based on Oligomer/Oligomer and Oligomer/Polymer

Xiaoe Jia, Chen Sun, Guichuan Zhang, Fei Huang, Baomin Xu, Yong Cao, Lei Ying, Cheng Zhou

Variations in the open-circuit voltage (Voc) of ternary organic solar cells are systematically investigated. The initial study of these devices consists of two electron-donating oligomers, S2 (two units) and S7 (seven units), and the electron-accepting [6,6]-phenyl C71 butyric acid methyl ester (PC71BM) and reveals that the Voc is continuously tunable due to the changing energy of the charge transfer state (Ect) of the active layers. Further investigation suggests that Voc is also continuously tunable upon change in Ect in a ternary blend system that consists of S2 and its corresponding polymer (P11):PC71BM. It is interesting to note that higher power conversion efficiencies can be obtained for both S2:S7:PC71BM and S2:P11:PC71BM ternary systems compared with their binary systems, which can be ascribed to an improved Voc due to the higher Ect and an improved fill factor due to the improved film morphology upon the incorporation of S2. These findings provide a new guideline for the future design of conjugated polymers for achieving higher performance of ternary organic solar cells. Tunable open-circuit voltages are realized in ternary organic solar cells based on oligomer/oligomer (S2/S7) and oligomer/polymer (S2/P11) as the photoactive layer, which can be correlated to the charge transfer state of these photoactive layers. It is interesting to note that the ternary systems of S2:S7:PC71BM and S2:P11:PC71BM exhibit higher power conversion efficiencies than their binary counterparts.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/marc.201700090