Journal of Materials Science, Vol.51, No.17, 8018-8026, 2016
Spirobifluorene-cored small molecules containing four diketopyrrolopyrrole arms for solution-processed organic solar cells
Spirobifluorene-linked three-dimensional small molecules of SF(DPP)(4) and SF(TDPP)(4) containing four diketopyrrolopyrrole arms were designed and synthesized. Both molecules displayed a broad and strong absorption in the region of 300-700 nm with suitable HOMO and LUMO energy levels as well as high charge carrier mobility. Meanwhile, solution-processed organic solar cells with a device structure of ITO/PEDOT:PSS/active layer/Ca/Al was also fabricated to investigate the photovoltaic properties of SF(DPP)(4) and SF(TDPP)(4). In contrast to that of star-shaped TPA(DPP)(3) in solar cells, enhanced photovoltaic performance with an impressive open circuit voltage of 0.95 V and short-circuit current density of 9.12 mA/cm(2) was achieved, leading to the maximum power conversion efficiency of 3.72 %. Our result here demonstrated that the three-dimensional-type small molecule in a D-A framework is a promising candidate as electron-donor materials for efficient organic solar cells.