Medium area, flexible single and tandem junction solar cells based on roll coated semi-random copolymers

We report on medium area (1 cm(2)) slot-die coated organic photovoltaic devices (OPVs) of a recently developed semi-random copolymer of poly-3-hexylthiophene and diketopyrrolopyrrole (P3HTT-DPP-10%) mixed with phenyl-C61-butyric acid methyl ester ([60] PCBM). The devices were prepared using a compact laboratory roll-coater using only slot-die coating and flexographic printing under ambient conditions on a flexible ITO-free substrate. In order to overcome a low J(SC) and FF obtained for single junction devices, devices were also prepared in a tandem geometry making it possible to employ thinner junction films. Power conversion efficiencies of up to 1.36% and 1.31% were achieved for the tandem and single junction geometries, respectively.