Key Takeaways & Executive Findings
- •• • A 110 nm-thick perovskite absorber on glass, initially reddish-brown, was transformed to vivid cyan using a 600 nm-thick ZnS/MgF2 multilayer, achieving an AVT of 6.5% while boosting power conversion efficiency by 20.9%—demonstrating that all-dielectric interference coatings can deliver aesthetic customization without sacrificing transmittance. • • On PET substrates, the same color transformation retained an AVT of 5.3% and enhanced efficiency by 10.4%, confirming the transferability of the inverse-design framework to flexible, lightweight substrates essential for building-integrated and wearable photovoltaics. • • The active learning algorithm mapped the attainable color gamut for distinct perovskite absorber thicknesses and AVT values, enabling user-defined colors with minimal spectral loss—a critical advance over absorptive metal layers that inherently reduce transmittance and efficiency. • • Future computational refinement from 20-bit to 50–100 bits via simulated annealing or several hundred bits via quantum annealing could enable sharper spectral control, higher color purity, and access to a broader chromaticity space, directly impacting the commercial viability of colored solar windows.
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Abstract
Urban architects increasingly seek solar windows that deliver both energy generation and aesthetic value. However, existing color-engineering strategies rely on absorptive metal layers or lack control over the achievable colors. Here, we present a modelling-guided inverse design strategy that integrates an all-dielectric (ZnS/MgF2) multilayer into semitransparent perovskite photovoltaics, enabling user-defined colors with minimal spectral loss. Leveraging an active learning algorithm, we mapped the attainable color gamut for ZnS/MgF2-coated devices with distinct perovskite absorber thicknesses and average visible transmittance (AVT) values. As a representative case, a device with a 110 nm-thick absorber on glass or polyethylene terephthalate (PET), initially exhibiting a reddish-brown tint, was transformed into vivid cyan using a 600 nm-thick all-dielectric multilayer. This tuning retained high AVT—6.5% on glass and 5.3% on PET—while enhancing power conversion efficiency by 20.9% and 10.4%, respectively. Real-world imaging confirmed enhanced aesthetics with see-through visibility, underscoring the practical potential of the inverse-design framework. Moreover, this approach is readily transferable to other thin film photovoltaics, providing a versatile route toward color customizable, transmittance-tunable, and high-efficiency solar windows for buildings, vehicles, and wearable electronics.
1. Introduction
In densely built urban areas, the deployment of photovoltaic (PV) systems is constrained by a lack of available space. Rooftop- and building-integrated photovoltaics (BIPV) can only provide limited capacity in city centers, and expanding these installations often conflicts with environmental sustainability goals. Clearing forests or other natural land for large PV arrays runs counter to the renewable energy ethos, as it leads to deforestation, habitat loss, and even marine ecosystem disruption when aquatic surfaces are used. In light of these challenges, integrating PV functionality into the built environment has become a compelling strategy for scaling up solar energy generation. Burgeoning architectural and automotive trends further amplify the demand for aesthetically pleasing solar solutions that do not compromise on performance.
Existing color-engineering strategies for semitransparent perovskite photovoltaics typically rely on absorptive metal layers or lack control over the achievable colors, resulting in significant spectral loss and reduced power conversion efficiency. These approaches fail to balance aesthetic requirements with energy generation, stalling widespread adoption in urban architecture and consumer electronics. The modelling-guided inverse design strategy presented here addresses this bottleneck by integrating an all-dielectric (ZnS/MgF2) multilayer into semitransparent perovskite devices, enabling user-defined colors with minimal spectral loss. By leveraging an active learning algorithm to map the attainable color gamut across different perovskite absorber thicknesses and average visible transmittance (AVT) values, this framework transforms a device with a 110 nm-thick absorber from reddish-brown to vivid cyan while retaining high AVT and enhancing power conversion efficiency by up to 20.9%.
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Seok-Beom Seo, Rira Kang, Eun-Joo Lee, So-Yeon Ju, Min Jae Lee, Byunghong Lee, Sun-Kyung Kim (2026). Modelling-Guided Inverse Design Strategy for Semitransparent Perovskite Photovoltaics with Customized Colors. Opto-Electronic Advances (光电进展). https://doi.org/10.29026/oea.2026.250218
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Frequently Asked Questions
What are the failure mechanisms under stress for the ZnS/MgF2 multilayer-coated semitransparent perovskite devices, and how do they affect long-term stability?
The research text does not provide specific degradation rates or failure mechanisms under stress. However, it acknowledges that robust encapsulation strategies are essential for improving device stability against photodegradation and moisture ingress, ultimately enabling higher stabilized efficiencies. Without such encapsulation, the all-dielectric multilayer and perovskite absorber are susceptible to environmental degradation, which could reduce AVT and power conversion efficiency over time.
How does the cost of the all-dielectric ZnS/MgF2 multilayer compare to legacy absorptive metal layers in semitransparent perovskite photovoltaics?
The text does not provide direct cost comparisons. However, the all-dielectric multilayer approach eliminates the need for absorptive metal layers, which inherently reduce transmittance and efficiency. By retaining high AVT (6.5% on glass, 5.3% on PET) and enhancing power conversion efficiency by 20.9% and 10.4%, respectively, the strategy may offer a more cost-effective route by maximizing energy yield per unit area, though material and deposition costs for ZnS/MgF2 multilayers require further assessment.
What are the scalability bottlenecks for manufacturing the ZnS/MgF2 multilayer-coated semitransparent perovskite photovoltaics, particularly for large-area solar windows?
The text mentions that emerging photovoltaic manufacturing techniques such as electrospray printing offer scalable routes that may enhance practicality for window-integrated applications. However, specific bottlenecks such as uniformity of the 600 nm-thick multilayer over large areas, deposition rate control, and integration with roll-to-roll processes for PET substrates are not detailed. The active learning algorithm's computational demands (20-bit representation) may also limit rapid optimization for high-throughput production.
How does the active learning algorithm's 20-bit digital representation constrain the achievable color gamut and spectral control, and what improvements are expected with finer discretization?
The 20-bit digital representation limits the precision of the inverse design, resulting in a restricted color gamut and suboptimal spectral control. Transitioning to 50–100 bits via simulated annealing or several hundred bits via quantum annealing could enable sharper spectral control, higher color purity, and access to a broader chromaticity space. This advancement would directly enhance the commercial viability of colored solar windows by allowing more vibrant and customized colors without compromising AVT or efficiency.
What is the impact of perovskite absorber thickness on the trade-off between average visible transmittance (AVT) and power conversion efficiency in the inverse-designed devices?
The text indicates that thinning the perovskite photoactive layer would increase baseline AVT and enlarge the attainable color gamut. In the representative case, a 110 nm-thick absorber on glass achieved an AVT of 6.5% and a 20.9% efficiency enhancement, while on PET the AVT was 5.3% with a 10.4% efficiency gain. This suggests that thinner absorbers favor higher AVT but may reduce efficiency, necessitating optimization via the inverse design framework to balance aesthetic and performance requirements.
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