Toward See-Through Optoelectronics: Transparent Light-Emitting Diodes and Solar Cells

Transparent light-emitting diodes (LEDs) and solar cells have attracted extensive attention as the most promising optoelectronic devices surpassing conventional opaque displays and photovoltaics. These transparent devices are particularly suitable for special applications including see-through display and building-integrated photovoltaics, for example, head-mounted displays, navigation displays on car windshields, smart windows, roofing, skylights, and facades. This review systematically evaluates the pros and cons of representative transparent conductive electrodes (TCEs) including transparent conductive oxides, ultrathin metal films, metal nanowires/meshes, conductive flexible polymers, carbon nanotubes, and graphene. A full-scale overview of recent studies on transparent organic LEDs, quantum dot LEDs, perovskite LEDs, dye-sensitized solar cells, organic solar cells, and perovskite solar cells using the above-mentioned TCEs as top electrodes, is also provided, summarizing information on state-of-the-art device performances. Finally, the key challenges in current transparent optoelectronic devices and a few potential proposals for developing highly efficient transparent devices are addressed in the last part. It is believed that, with the rapid development of novel optoelectronic materials and fabrication technologies, there will be a bright prospect for transparent optoelectronic devices and their related applications in the near future.