Flexible and stretchable crystalline silicon photovoltaic modules

In the context of the urgent Net-zero energy transition to counter the climate crisis caused by global warming, photovoltaics (PV) technology is becoming a leading force for reducing CO2 emission. Crystalline silicon (c-Si) PV, as a mature, stable, and efficient technology pathway, provides an ideal platform to extend PV applications beyond conventional solar farm to Building Integrated Photovoltaics (BIPV), Agrivoltaics (AgriPV), and wearable systems. However, the need for conformal integration on curved surfaces and for dynamic control of light and shading in BIPV and AgriPV as well as meeting the demand of joint movement of wearables present challenges that traditional rigid panels or static semi-transparent PV modules cannot solve. This work therefore proposes a flexible, stretchable c-Si module design with dynamically adjustable transmittance, aimed at applications requiring both surface conformity, stretchability and controlled light regulation. The early stage focused on structures of elastomer substrate and island–bridge with serpentine interconnects. Sequentially coupled mechanical–optical simulations were used to evaluate stretch response, failure modes, and in-plane light modulation. Although mechanically compliance can be expected, this approach showed limitations in active solar cell per area, stretchability, control complexity, interconnect reliability, and scalability, restricting its use in BIPV, AgriPV, and wearables. To overcome these challenges, three auxetic rotating polygon structures were then developed: Auxetic Rotating Squares (ARS), isosceles-right Triangles (ARTir), and equilateral Triangles (ARTe). Under concentric mounting (CM) and side-aligned mounting (SM) configurations, simulations and prototypes confirmed that controllable transmittance can be achieved with single-axis stretching owing to the auxetic effect: ARTir 45–86%, ARTe 45–80%, and ARS 43–62%. With highly transparent polyurethane encapsulation, high compliance and durability has been achieved, while the auxetic structure providing greater stretchability, simplified transmittance controlling mechanism, and potential for modularization to meet the demand of large deployment. In summary, the auxetic structures balance flexibility, transmittance adjustability and power density, and may significantly extend the application of c-Si to adaptive BIPV/AgriPV and self-powered wearable devices. Furthermore, the auxetic rotating polygons are highly versatile and could be combined with organic photovoltaics (OPVs) to merge wavelength-selective transmission with mechanical adjustability, further enhancing dynamic light management.