Breakthrough in Building-Integrated Photovoltaics: Semi-Transparent Solar Cells Reach Record Efficiency

A team of researchers has developed a new parameter, FoMLUE, to evaluate the potential of photoactive materials for semi-transparent organic photovoltaics (ST-OPVs), paving the way for their extensive commercial applications.

A paper detailing the study, “Semitransparent organic photovoltaics with wide geographical adaptability as sustainable smart windows,” has been published in Nature Communications.

Transparent solar cells have the potential to be integrated into windows, screens, and other surfaces, revolutionizing the renewable energy sector. However, challenges such as balancing transparency with power conversion efficiency need to be addressed.

Semi-transparent organic photovoltaics (ST-OPVs) combine efficient energy generation with visually appealing design, making them a focus of significant research efforts.

With their discrete absorption, cost-effective production, and eco-friendly nature, ST-OPVs hold great promise for building-integrated photovoltaics (BIPV).

To maximize their potential in the BIPV market and beyond, researchers have combined various materials and utilized advanced device engineering technologies to improve the efficiency and stability of ST-OPVs. They have also ensured that the product’s color appears natural under sunlight, preserving the building’s aesthetic appeal.

Prof. Li Gang and his team, along with Research Fellow Dr. Yu Jiangsheng, have introduced a dimensionless parameter, FoMLUE, to evaluate a range of classic photoactive materials. This parameter considers the materials’ average visual transmittance, bandgap, and current density by analyzing their normalized absorbance.

The researchers discovered that ST-OPVs based on ternary materials with the highest FoMLUE values exhibited improved thermal insulation and operational stability compared to other options, achieving a record light utilization efficiency of 6.05%—the highest reported figure of merit for any semi-transparent solar cell.

Their research also highlighted the impact of geographical factors on ST-OPV performance. By developing a transient model to simulate power output and assess its effect on building space cooling and heating loads in 371 Chinese cities, the team found that over 90% of cities experienced annual load reductions. Regions with hot summers and warm winters were identified as ideal for ST-OPV glazed windows, with potential annual energy savings of up to 1.43 GJ m⁻².

Prof. Li emphasized the versatility and adaptability of high-performance ST-OPVs in creating sustainable and energy-efficient smart windows that do not compromise architectural design, underscoring their promising commercial prospects.

Future research will focus on enhancing the long-term stability of ST-OPVs and scaling up development to large-area solar modules to facilitate commercialization.