Enhancing heat stress tolerance in organic romaine lettuce using crystalline silicon and red, blue & green-colored thin film agrivoltaic systems

• Agrivoltaics boosted lettuce yield up to 483% under heat stress. • 60% Cd-Te and 44% c-Si modules delivered the best productivity gains. • Partial shading improved plant height, leaf number, and biomass. • Agrivoltaics could add CAD $68B value and 6.3 Mt CO 2 cuts in 25 years. • Crop-specific spectral design is key for agrivoltaic system success. Climate destabilization is increasingly disrupting global agriculture. Agrivoltaics is an emerging solution to this challenge that simultaneously uses land for solar photovoltaic (PV) electricity generation and crop cultivation. This study investigates the performance of the heat sensitive crop of organic romaine lettuce under a broad range of agrivoltaic conditions outdoors alongside un-shaded controls. Twelve agrivoltaic configurations of varying crystalline silicon wafer-based and thin-film solar PV modules, differed in magnitude and spectra of light transmittance, shading patterns, and spatial coverage. During high-temperature stress conditions, the results show agrivoltaic treatments increased lettuce fresh weight by over 400% compared to unshaded control plants and by over 200% relative to the national average yield. Notably, 60% transparent colored thin-film PV modules and 44% transparent crystalline silicon-based PV modules delivered the highest productivity gains, underscoring the critical role of optimized shading intensity and spectral quality in promoting plant growth. Morphological traits such as plant height and leaf number exhibited strong positive correlations with biomass accumulation, validating the physiological benefits of partial shading and spectral filtering. The economic value of lettuce is roughly four times the value of agrivoltaic-generated electricity on equivalent land area. Overall, the results demonstrate that agrivoltaic systems can enhance romaine lettuce production during hot summers while simultaneously contributing to climate-smart agriculture and sustainable energy generation. If scaled to protect Canada’s entire lettuce crop, agrivoltaics would result in major emissions reductions as well with the total carbon dioxide emission reduction being between 2.5 Mt (thin-film PV) and 6.4 Mt (silicon PV).