Organic Photovoltaic Cells for Indoor Applications: Opportunities and Challenges.

With the growing development of the Internet of Things, organic photovoltaic (OPV) cells are highly desirable for indoor applications because of the unique features of light weight, flexibility, and coloration. Emission spectra of the commonly used indoor light sources are much narrower with lower light intensity as compared to the standard solar spectrum. High tunability in optical absorption, insensitivity to series resistance and the active layer thickness, and mild operating conditions make indoor OPV cells promising as a practically relevant technology. Currently, the OPV module has obtained a power conversion efficiency of over 20%, with excellent stability under indoor conditions. However, at the present stage, the device physics investigations and material design strategies developed in an OPV cell for indoor applications lag behind those for outdoor applications. In particular, the emerging characterizations in photovoltaic measurements have severely affected the reliability of reports. This Spotlight on Applications highlights these opportunities and challenges of OPV cells for indoor applications and reviews the recent progress in indoor OPV cells. In addition, we summarize some studies related to accurate measurement and provide some recommendations.