Interface engineering is a critical strategy for improving the performance of polymer solar cells. A good interfacial material should fulfill several requirements including 1) good charge selectivity to improve the charge collection efficiency at the corresponding electrodes, 2) matched energy levels with the conduction band and valence band of the light harvesting film to maximize the photovoltage of the solar cells, 3) high conductivity to minimize the interfacial resistance loss and forming Ohmic contact with the electrodes. In addition to interface engineering, optical management is another powerful method to enhance the performance of polymer solar cells by maximizing the light harvesting property of the devices. The capability to use optical model to precisely predict the light propagation property and charge generation rate within the devices allows us to design optimal device architectures with maximum performance. In this talk I will discuss how to combine these two key strategies to improve performance of polymer solar cells. The design of new conjugated polymer-based interfacial materials with desired electrical conductivity, energy levels and processibility allows us to improve the charge collection efficiency and compatibility for polymer solar cells based on fullerene [2,3] and non-fullerene acceptors. Finally I will also discuss how to combine both interface engineering and optical modeling to design and fabricate very high performance tandem [5,6] and semitransparent polymer solar cells.
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