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

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. [Display omitted] •Correlations between electrostatic force and interaction energy are established•Domain purity of the film can be modulated by tuning the donor:acceptor ESP difference•A high PCE of 15.3% is demonstrated in a PT-based all-polymer solar cell It is of great scientific and practical significance to develop efficient all-polymer solar cells (all-PSCs) based on low-cost photoactive materials, which could be realized by exploring novel donor:acceptor systems. However, the correlation between molecular structures and morphological characteristics still remains unclear. In this work, we present a deep understanding of the intermolecular interactions between the conjugated molecular systems via considering molecular electrostatic potential (ESP) at the molecular level. The electrostatic force-bulk morphology relationship is established. This study highlights the modulation of ESP can be regarded a feasible molecular design strategy for complex blend systems and boost their PCEs to a new stage. Hou and co-workers demonstrated the correlation between molecular structures and morphological characteristics in polythiophenes:polymer acceptor combinations via considering electrostatic force. By modulating the intermolecular interaction between the polymer acceptor (PY-IT) and two polythiophenes (P3HT and PDCBT), the donor:accepto