Organic and Inorganic Photoactive Absorbers for Wavelength‐Selective Transparent Photovoltaic Devices: Focus Review

The present status of wavelength‐selective transparent photovoltaic (TPV) devices for green buildings and self‐powered wireless sensors is comprehensively reviewed. Photoactive absorbers for both UV and near‐infrared (NIR)‐selective TPV are discussed. UV‐selective devices based on engineered small organic molecules have demonstrated high transparency (>80%). However, their power conversion efficiency (PCE) is ≈1%. Higher PCE of 3.15% and transparency of 51.4% are obtained from the bulk heterojunction (BHJ) of a wide energy gap conjugated polymer and nonfullerene acceptor (NFA). The highest transparency of 84.6% together with device stability and scalability is realized for CsPbCl 2.5 Br 0.5 perovskite absorbers. The few reported NIR‐selective TPV devices are all organic solar cells. Using BHJs comprising ultranarrow energy gap conjugated polymer and NFA, a PCE of 5.74% and transparency of ≈60% can be obtained. However, current IR‐selective devices are generally limited by an absorption tail that encroaches into the visible region and result in suboptimal color rendering. To address this, a new spectral range ratio (SRR) parameter is proposed to classify absorbers for IR‐selective TPV devices. A molecular design strategy to increase the SRR based on frontier molecular orbital theory is outlined.