Modulation of Donor-Acceptor Interface through Thermal Treatment for Efficient Bilayer Organic Solar Cells

Abstract

In this article, we demonstrate the effect of donor-acceptor (D-A) interface on the performance of bilayer organic solar cells. Solution processing was used to develop liquid crystal poly(9,9'-dioctylfluorene-co-bithiophene) (F8T2) polymer films and variable morphology of the films was achieved by varying the annealing temperature. The morphology of the annealed active layers signature a well-aligned nanodomain feature with an interdegitated structure at 200 degrees C. The devices with bilayer configuration, ITO/PEDOT:PSS/F8T2/C(70)/Al, have yielded a power conversion efficiency (PCE) of 3.4(+/- 0.2)% under 1 sun incident radiation. We attribute the high PCE to the increased D-A junction interface and balanced charge transport between electron/hole transport layers.