Toward Efficient Tandem Organic Solar Cells: From Materials to Device Engineering.

Organic solar cells (OSCs) have demonstrated considerable potential in utilizing renewable solar energy because of their distinct advantages of light weight, low cost, and good flexibility. In the past decade, tremendous development in power conversion efficiency (PCE) from ∼7% to more than 17% has been witnessed. Among the various strategies of improving the PCE of OSCs, tandem structure is one of the most effective ways. In this Spotlight on Applications, we first introduce active-layer materials that we developed and selected for tandem OSC construction. We then emphasize an interconnecting layer (ICL) that we developed based on polymeric electron-transport layers. Benefiting from the organic nature of polymeric materials, the electron extraction ability and charge-transport ability of the organic electron-transport layer can be easily tuned by modifying the molecular structure or using a binary strategy, which enables us to obtain highly efficient tandem OSCs. Moreover, an ICL composed of a polymeric electron and hole-transport layer offers intrinsic advantage in obtaining a flexible tandem device and is compatible with the printing technique for fabricating large-area devices. After that, the application of the transfer matrix modeling method in predicting the best tandem OSCs architecture is introduced. Lastly, the possible research interests of tandem OSCs in the future from our point of view is discussed.