An ambipolar polymer additive for enhanced open circuit voltage in a bulk heterojunction solar cells

摘要

Open circuit voltage (VOC) of organic bulk heterojunction solar cell is extended by the addition of a 20 wt % of F8TBT, an ambipolar polymer in the active layer matrixes (P3HT:PCBM) and then spin casted (1000 rpm/30 s) in the optimized devices on the PEDOT:PSS layer of the ITO glass. A substantial increase in the open circuit voltage from approximately 0.61-0.88 V (44.26%) has been observed with slight increase in efficiency up to 1.91% in the fabricated devices. However, further increment of F8TBT content to 40 wt % reduces the photovoltaic efficiency and affects the J(SC) values remarkably, possibly due the excess amount of resistance developed. The enhancement of VOC is attributed to the ambipolar nature of F8TBT polymer which facilitates the generated electron and hole transfer at the respective electrodes, enhanced pi-pi* conjugation in polymer matrix, a superior nanoscale separation, and better molecular conformation at the film interface, thus giving an ample opportunities to explore the impact of blending of materials rather than depositing a thin buffer layer by expensive vapor phase technologies. The details of electrical and microstructure characterization of the film were analyzed by AFM, SEM, UV-Vis, J-V characteristics, and EQE techniques. (c) 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43042.