Transparent Polymer Photovoltaics for Solar Energy Harvesting and Beyond

Polymer photovoltaics have become a promising alternative energy due to lightweight properties, environmental friendliness, and solution processability. Transparent organic photovoltaics in particular have been recently receiving more attention in the photovoltaics field due to their unique potential in future applications beyond mere harvesting of solar energy. This perspective is further enhanced by the recent developments of high-performance polymer photovoltaics (including infrared absorbing materials and devices) that could achieve superior visible transparency and power conversion efficiency. To realize high-performance transparent organic photovoltaics, the main strategy is to shift the active-layer absorption spectrum to the infrared region by designing new low-bandgap donors and non-fullerene acceptors, and to reduce the invalid absorption by developing new transparent electrode materials. The potential applications are diverse, especially for spectrum-sensitive ones such as the greenhouse in agriculture. Finally, some key research areas of transparent organic photovoltaics that may deserve further attention are discussed. Polymer photovoltaics are a promising alternative energy for visible-spectrum applications because the absorption spectra of organic semiconductors, including polymer and small-molecule types, are not continuous as in inorganic semiconductors. As a result, the design of organic materials is able to pass visible light and absorb non-visible light such as the infrared. According to the energy distribution of the solar spectrum, more than a half of solar light is distributed within the infrared region. The theoretical efficiency of polymer photovoltaics with only infrared absorption therefore can be as high as a device with only visible absorption. Accordingly, we present a perspective that concisely reviews the developments in transparent polymer photovoltaics and their potential applications in order to engender new ideas on achieving superior transparency, power conversion efficiency, and more practical utilities. Because of an emergent demand for visible-spectrum applications in daily life, organic-based photovoltaics are thought to be a strong candidate to fulfill this need. This article concisely reviews the developments in polymer and small-molecule materials for achieving effective transparent photovoltaic devices and their potential applications in order to engender new ideas on achieving superior transparency, power conversion efficiency, and more practical uses.