Morphology control by tuning electrostatic interactions for efficient polythiophene-based all-polymer solar cells

Summary

Polythiophenes are one of the most classical donors for organic solar cells, which have simple chemical structures and thus low production costs. However, their photovoltaic performance is lagging far behind the donor-acceptor-type polymers, especially when blending with polymer acceptors, where morphology control is a huge challenge. Here, we systematically study the intermolecular interaction in polythiophene:polymer acceptor (PY-IT) combinations and establish a rational relationship between chemical structure and blend miscibility. Our results suggest that the electrostatic force plays a key role in determining the donor:acceptor intermolecular interaction energy. Introducing electron-withdrawing functional groups into the backbone of P3HT can increase the electrostatic potential (ESP) and suppress the intermolecular interaction with PY-IT. Due to the proper miscibility and improved domain purity, the corresponding polymer PDCBT records a high-power conversion efficiency (PCE) of 15.3%, which is the highest value in polythiophene-based all-polymer solar cells (all-PSCs) and crucial for advancing their practical applications.