Efficient planar-mixed heterojunction photovoltaic device based on subphthalocyanine:C70 structure

Wei-Cheng Su; Shun-Wei Liu; Ching-Wen Cheng; Chia-Chang Chou; Jia-Cing Huang; Chih-Chien Lee

doi:10.1117/12.929562

13 September 2012 Efficient planar-mixed heterojunction photovoltaic device based on subphthalocyanine:C₇₀ structure

Wei-Cheng Su, Shun-Wei Liu, Ching-Wen Cheng, Chia-Chang Chou, Jia-Cing Huang, Chih-Chien Lee

Proceedings Volume 8477, Organic Photovoltaics XIII; 84771E (2012) https://doi.org/10.1117/12.929562
Event: SPIE Organic Photonics + Electronics, 2012, San Diego, California, United States

Abstract

In this report, we demonstrate an efficient planar-mixed heterojunction organic photovoltaic (OPV) device employing a mixed structure of subphthalocyanine (SubPc) donor and C₇₀ acceptor. Compared to a SubPc:C₆₀ cell, the SubPc:C₇₀ cell exhibits high performance with a fill factor (FF) of 52%, short-circuit current density (J_SC) of 8.8 mA/cm², open-circuit voltage (V_OC) of 1 V, and power conversion efficiency of 4.6% under air-mass 1.5 G illumination (1 sun). The high V_OC is mainly due to the wide interface gap between SubPc and C₇₀ as in the SubPc:C₆₀ device. On comparing the absorption spectra of C₇₀ and C₆₀, C₇₀ shows the higher absorption coefficient and wider absorption band, leading to the significantly improved J_SC. Moreover, the FF of the device using C₇₀ is enhanced to 52%; by comparison it is 45% when using C₆₀. In order to understand this phenomenon, the space-charge limited current is measured for estimating the carrier mobility of SubPc, C₇₀, and C₆₀. It reveals that the electron mobility of C₇₀ is lower than that of C₆₀ by orders of magnitude but is close to the hole mobility of SubPc. As a result, a better charge balance condition is achieved when SubPc is blended with C₇₀ and therefore a higher FF is obtained. Consequently, C₇₀ seems to be a more suitable acceptor for the mixed structure to develop a highly efficient OPV device due to the improvements in both electrical and optical properties.

Citation Download Citation

Wei-Cheng Su, Shun-Wei Liu, Ching-Wen Cheng, Chia-Chang Chou, Jia-Cing Huang, and Chih-Chien Lee "Efficient planar-mixed heterojunction photovoltaic device based on subphthalocyanine:C₇₀ structure", Proc. SPIE 8477, Organic Photovoltaics XIII, 84771E (13 September 2012); https://doi.org/10.1117/12.929562

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