Novel conjugated polymer for organic photovoltaics: Synthesis and device optimization

• We investigate photovoltaic performance of a conjugated polymer (CP).
• Degree of polymer aggregation is tuned and device performance is correlated with the aggregation of CP.
• Main methods applied for aggregation are additive- and CO2 liquid-assisted annealings.
• The change of surface morphology induced by the aggregation of CP is reviewed.

A novel conjugated polymer, TdTB, having an alternating configuration of electron donor and acceptor was synthesized for organic photovoltaic (OPV) application. Intramolecular charge transfer made TdTB exhibit bimodal-shaped absorption in visible region, which secured about 4% power conversion efficiency (PCE) via enhanced absorption efficiency. OPV cells could be further optimized by means of additive-assisted annealing or additional super critical CO2 liquid treatment after additive annealing, and more developed TdTB aggregation was achieved. Consequently, their performances were dramatically improved about 17% and 33%, compared to the non-annealed PV cell, giving 4.65 and 5.27% PCEs, respectively.

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