A comparative study of the photovoltaic performances of terpolymers and ternary systems

Random terpolymers were synthesized from the electron-rich unit thiophene as the donor and two electron-deficient units with complementary absorption as the acceptor. Polymer solar cells (PSCs) fabricated from these terpolymers were compared with those fabricated from the ternary blends of two alternating polymers to explore the best strategy for extending the light absorption range. The two approaches showed similar open-circuit voltages (Voc) but different short-circuit current densities (Jsc). The terpolymer strategy broadened the light absorption range and provided a high power conversion efficiency (PCE) of 5.8%. This is due to a high Jsc and high hole mobility. The device fabricated from the ternary blend exhibited a lower PCE (3.5%) compared to those fabricated from the terpolymers and alternating polymer blends due to the morphological incompatibility of the donor polymers. Our results illustrate the potential of the terpolymer systems as a promising strategy to effectively increase the light absorption and thereby performance of PSCs by combining two morphologically incompatible polymers.