Semi-transparent organic photovoltaics.

As an economical solar energy conversion technology, organic photovoltaics (OPVs) are regarded as a promising solution to environmental problems and energy challenges. With the highest efficiency of OPVs exceeding 20%, the research focus will shift from efficiency-oriented aspects to commercialization-oriented aspects in the near future. Semi-transparent OPVs (STOPVs) are one of the most possible commercialized forms of OPVs, and have achieved power conversion efficiency over 14% with average visible light transmittance over 20% so far. In this tutorial review, we first systematically summarize the device structures, operating principles and evaluation parameters of STOPVs, and compare them with those of opaque OPVs. Then, strategies to construct high-performance STOPVs by cooperatively optimizing materials and devices are proposed. Methods to realize the scale-up of STOPVs in terms of minimization of electrode and interconnect resistance are summarized. The potential applications of STOPVs in multifunctional windows, agrivoltaics and floating photovoltaics are also discussed. Finally, this review highlights major challenges and research directions that need to be addressed prior to the future commercialization of STOPVs.