Composite materials for interfacial engineering of organic solar cells

As a leading category of emerging photovoltaic technologies, organic solar cells (OSCs) have achieved notable breakthroughs in power conversion efficiency (now reaching 21%), demonstrating considerable potential for practical application. Nonetheless, they continue to face critical challenges including inadequate long-term operational stability and severe performance degradation when scaled up via printing techniques. Engineering the interfacial layers (ILs), particularly through the development of ILs with composite components, is widely considered a feasible approach to address these challenges in OSCs. In the review, we will focus on the discussion of representative composite ILs for OSCs, including both hole- and electron-transporting layers (HTLs and ETLs), by dividing them into three categories, i.e., inorganic composite HTLs/ETLs, organic composite HTLs/ETLs and organic-inorganic hybrid HTLs/ETLs. The interplay between different components in these ILs and the influence of interfacial doping/mixing on the performance of OSCs will be elaborated. We will also pay attention to the chemical and physical stability of these composite ILs as well as their potential in the up-scaling process.