Positive side of disorder: Statistical fluorene-carbazole-TTBTBTT terpolymers show improved optoelectronic and photovoltaic properties compared to the regioregular structures

We report a systematic study of a family of statistical fluorene-carbazole-TTBTBTT terpolymers with a variable fluorene-to-carbazole ratio. It has been shown that changing the molecular composition of the polymers affects significantly their characteristics such as absorption spectrum, extinction coefficients, position of the frontier energy levels and charge carrier mobility. Power conversion efficiencies of 6.4–7.0% were obtained for the best-performing carbazole-rich and fluorene-rich terpolymers. Most importantly, we showed that optoelectronic properties (particularly, the extinction coefficients defining the light harvesting ability) and photovoltaic performances of conventional regioregular copolymers in the blends with [70]PCBM can be significantly improved simply by introducing a “rational disorder” in the polymer chains using statistical copolymerization of certain building blocks taken in appropriate ratios

Impact of charge carrier mobility and electrode selectivity on the performance of organic solar cells

Low charge carrier mobilities as often observed for photoactive materials of organic solar cells have significant impact on their performance. They cause accumulation of charge carriers which can be described quantitatively by a nonohmic transport resistance in the framework of an analytical model. Further addressed in this work is surface recombination stemming from insufficient electrode selectivity which is another factor limiting the performance of organic solar cells