n-Type polymer electron acceptors for organic solar cells

n-Type polymer electron acceptors have attracted significant attention due to their advantages such as adjustable energy levels and bandgaps, high absorption coefficients and excellent electrical and photovoltaic properties. Thus, designing and synthesizing high-performance n-type polymer electron acceptors have become one of the mainstream research topics of organic solar cells (OSCs). Due to the rapid development of n-type polymer electron acceptors, the power conversion efficiencies (PCEs) of related OSCs have increased to 15-174 in the last few years. Intense investigations on molecular structure tailoring and new n-type polymer electron acceptors have been reported. These developed n-type polymer electron acceptors play a vital role in improving the photovoltaic performance. In this review, we summarize the recent advances in the innovation of n-type polymer electron acceptors and structure-property relationships and the compatibility of donors and acceptors as well as the guidelines for future structure designs, morphology control and direction for the development of n-type polymer electron acceptors.