Composite interlayer consisting of alcohol-soluble polyfluorene and carbon nanotubes for efficient polymer solar cells

Abstract

We report the synthesis of composite interlayers by using alcohol-soluble polyfluorene-wrapped single-walled carbon nanotubes (ASP-wrapped SWNTs) and their application to the electron transport layer in efficient organic solar cells. The ASP enable the individual dispersion of SWNTs in solution. Impressively, ASP-wrapped SWNTs solutions are stable for 54 days, indicating very high dispersion stability. Using the ASP-wrapped SWNTs as a cathode interlayer on zinc oxide nanoparticles (ZnO NPs), 9.45% of power conversion efficiency (PCE) can be obtained in PTB7-th:PC71BM-based organic solar cells, which is mainly attributed to the improvement of the short circuit current. Performance enhancements of 18% and 17% were achieved compared to those of pure ZnO NPs and ASP on ZnO NPs, respectively. The improvement of solar cell performance originates from an increased internal quantum efficiency, balanced mobility between electrons and holes, and minimization of charge recombination.