Spectrum Splitter Case Study

Spectrum splitters enhance energy conversion and crop productivity by directing specific wavelengths to optimized photovoltaic cells or plants.Overview of Spectrum SplittersSpectrum splitters are photonic devices that separate incoming light into different wavelength bands, directing each band to a target system optimized for that spectrum. In photovoltaics, this allows lateral tandem solar cells to overcome the limitations of single-junction cells, which cannot efficiently convert the full solar spectrum. By splitting light, high-energy photons are directed to high-bandgap cells, while lower-energy photons are sent to low-bandgap cells, reducing thermalization losses and improving overall power conversion efficiency (PCE) .Design and OptimizationRecent studies have demonstrated two-layer solar spectral splitters designed using inverse design techniques. These devices use structured interfaces or metasurfaces to redirect light efficiently across a wide range of incidence angles. The first layer redirects light toward a single angle, while the second layer distributes it spectrally to the laterally arranged subcells. Simulations using Fourier optics and differentiable programming frameworks like JAX allow optimization of phase masks to maximize the average current generated by the tandem cells . This approach addresses the degradation seen in single-layer splitters at oblique angles, maintaining high efficiency over a broader angular range.Applications in Concentrated PV-Thermal SystemsIn concentrated photovoltaic-thermal (CPV-T) collectors, spectrum splitters act as optical filters, allowing wavelengths suitable for silicon PV cells (500–1100 nm) to pass while reflecting UV and IR light to a secondary thermal absorber. This reduces PV cell operating temperatures by 30–35°C, improving electrical efficiency (~22%) and enabling simultaneous high-grade thermal energy extraction . CPV-T systems with spectrum splitting have been evaluated for harsh climates, showing cost-effective electricity and heat production with reduced CO₂ emissions .Agricultural ApplicationsSpectrum splitting technology (SST) has also been applied in agrivoltaic systems to balance energy generation and crop growth. For example, soybeans grown under spectrum-splitting and concentrated APV systems (SCAPV) showed increased soluble sugar content (4.1%) and oleic acid content (2.1%), along with higher fresh weight of grains and leaves compared to open-air controls. This demonstrates that SST can optimize light quality for photosynthesis while maintaining PV energy production .Key OutcomesEnhanced photovoltaic efficiency: Lateral tandem cells with two-layer splitters achieve higher PCE across a wide range of angles .Thermal management: CPV-T collectors with splitters reduce PV cell temperature, improving electrical output and enabling thermal energy harvesting .Agricultural benefits: SST improves crop physiology, yield, and quality in agrivoltaic setups .Economic and environmental impact: CPV-T systems with spectrum splitting show competitive LCOE and LCOH values and reduced CO₂ emissions .ConclusionSpectrum splitters represent a versatile technology bridging energy efficiency and sustainable agriculture. By tailoring light distribution to the specific needs of PV cells or crops, they enhance performance, reduce losses, and enable multi-functional solar systems. Advances in inverse design, metasurfaces, and multi-layer architectures continue to expand their practical applications in both energy and agrivoltaic sectors.