Progress in semitransparent solar panels: Materials, efficiency, and applications

This review provides a comprehensive overview of the progress in semitransparent solar panels, a critical technology for building-integrated photovoltaics (BIPV), energy-generating windows, and agrivoltaics. The paper traces the evolution and outlines the state-of-the-art of core technologies, including dye-sensitized solar cells (DSSCs), organic photovoltaics (OPVs), perovskite solar cells (PSCs), luminescent solar concentrators (LSCs), colloidal quantum dots, transparent crystalline silicon (c-Si), and ultrathin Cu(In,Ga)Se2 (CIGS) devices. A central theme is the inherent tradeoff between power conversion efficiency (PCE) and average visible transmittance (AVT), which defines the application space for each technology. Significant progress has been achieved across multiple semitransparent photovoltaic platforms, although reported values must be interpreted in the context of transparency level, device area, and measurement conditions. In opaque reference devices, PSCs and tandem architectures have surpassed 26% and 33.7% PCE, respectively, illustrating the maturity ceiling of the material platform. In contrast, semitransparent PSCs typically operate at lower PCE but over a wide AVT range depending on absorber thickness and electrode design. OPVs offer esthetic versatility with tunable, vibrant colors achieved through microcavity engineering, reaching over 15% PCE at moderate transparency (AVT ≈ 46%). LSCs prioritize transparency, achieving AVT values of up to 92% through ultraviolet absorption and edge emission, albeit with lower PCEs around 1.4%. Innovations in materials and device architecture are explored in detail. These include the development of metal-free dyes and tandem structures in DSSCs; non-fullerene acceptors and scalable peel-off patterning for OPVs; advanced passivation strategies and strain regulation for PSC stability; and lead-free I–III–VI quantum dots to address toxicity concerns. A notable advancement is the development of transparent c-Si solar cells using micropore arrays and all-back-contact architectures, which enable color-neutral modules with 14.7% PCE at 20% AVT. Similarly, ultrathin CIGS devices have achieved over 10% PCE with ∼ 12% AVT through optical management strategies. The review also examines practical applications through case studies, including the performance of BIPV systems in real-world conditions, the use of spectrally selective films in agrivoltaics to simultaneously support plant growth and generate electricity, and the design of hybrid photovoltaic–thermal windows that produce both electricity and heat. Overall, this work encapsulates the dynamic progress of semitransparent photovoltaics, charting their transition from laboratory-scale concepts to commercially promising solutions poised to transform architectural and agricultural surfaces into active power-generating assets.