Functionalized and reduced graphene oxide as hole transport layer and for use in ternary organic solar cell

Here is reported the performance of organic solar cells (OSCs) by using a new graphene oxide derivative as hole transport layer (HTL). OSCs are based on the PTB7:PC71BM blend as active layer and the alternative top electrode Field's metal (Bi/In/Sn: 32.5%, 51%, 16.5%), which can be easily deposited through a vacuum-free process at regular atmosphere and low temperature (90 degrees C). Graphene oxide (GO) was chemically functionalized and reduced with pentafluorophenylhydrazine, this fluorinated reduced graphene oxide (F-5-rGO) was suspended in dimethylformamide for easy deposit by wet techniques such as spin-cast. F-5-rGO has a work-function of 5.1 eV due to the high electronegativity of fluorine atoms incorporated into the GO sheets. The best achieved PCE of the OSCs fabricated for a single layer of F-5-rGO was 5.82%. An enhanced PCE of 7.67% when F-5-GO was used as interlayer between ITO and PEDOT:PSS was reached (PCE of PEDOT:PSS-based was 7.29%). Additionally, functionalized and reduced (chemically) graphene oxide (H-5-rGO) was also obtained from GO treated with phenylhydrazine, and ternary OSCs were also prepared by adding H-5-rGO to the PTB7:PC71BM blend at different weight ratios: 0, 3, and 6%. The best results were achieved with 3% of H-5-rGO: OSCs presented a PCE of 7.56%.