Photovoltaic cells have recently attracted considerable attention for indoor energy harvesting for low-power-consumption electronic products due to the rapid growth of the Internet of Things (IoT). The IoT platform is being developed with a vision of connecting a variety of wireless electronic devices, such as sensors, household products, and personal data storage devices, which will be able to sense and communicate with their internal states or the external environment. A self-sustainable power source is required to power such devices under low light indoor environments. Inorganic photovoltaic cells show excellent device performance under 1 Sun illumination and dominate the market for outdoor applications. However, their performance is limited for indoor applications with low incident light intensities as they exhibit low photo-voltage. Among the emerging photovoltaic technologies, organic photovoltaics have unique advantages, including solution processibility, flexibility, and lightweight tailorable design; hence, they are considered the best solution for indoor light harvesting applications due to their high photo-voltage, strong absorption of UV-visible wavelengths, and a spectral response similar to that emitted by modern indoor lighting systems. In this review article, we discuss the factors affecting device performance of different photovoltaic technologies under low incident light intensities or indoor conditions and provide a comprehensive analysis of future opportunities for enhancing indoor performance of the photovoltaic devices. Furthermore, we discuss some of the results of semi-transparent organic solar cell which is operated under complex environmental conditions like low illumination, incident light angle etc. Based on the results, one can suggest that semi-transparent organic solar cell is more suitable for progressive indoor solar cell. After highlighting the factors that limit indoor device performance of photovoltaic cells, we discuss potential applications of IoT devices powered by organic photovoltaic cells in indoor lighting environments.

Indoor photovoltaics (IPVs) have great potential to provide a self‐sustaining power source for Internet‐of‐Things (IoT) devices. The rapid growth in demand for low‐power IoT devices for indoor application not only boosts the development of high‐performance IPVs, but also promotes the electronics and semiconductor industry for the design and development of ultra‐low‐power IoT systems. In this Review, the recent progress in IPV technologies, design rules, market trends, and future prospects for highly efficient indoor photovoltaics are discussed. Special attention is given to the progress and development of organic photovoltaics (OPVs), which demonstrate great possibilities for IPVs, owing to their bandgap tunability, high absorbance coefficient, semitransparency, solution processability, and easy large‐area manufacturing on flexible substrates. Highly efficient indoor organic photovoltaics (IOPVs) can be realized through designing efficient donor and acceptor absorber materials that have good spectral responses in the visible region and better energy‐aligned interfacial layers, and through modulation of optical properties. Interfacial engineering, photovoltage losses, device stability, and large‐area organic photovoltaic modules are surveyed to understand the mechanisms of efficient power conversion and challenges for IOPVs under indoor conditions as a self‐sustaining power source for IoT devices. Finally, the prospects for further improve in IOPV device performance and practical aspects of integrating IOPVs in low‐power IoT devices are discussed.

Flexible organic photovoltaics and energy storage systems have profound implications for future wearable electronics. Here, the authors discuss the transformative potential and challenges associated with the integrative design of these systems for energy harvesting.