Researchers at Italy's Institute for Microelectronics and Microsystems, part of the National Research Council (IMM-CNR), working with colleagues at the National Research Council's Institute of BioEconomy (IBE-CNR), have developed a semi-transparent perovskite solar cell architecture designed to deliver more naturally balanced light to crops grown underneath, for agrivoltaic applications. The work builds on the same team's earlier study showing that a CsPbI₃ perovskite rooftop could support healthy radicchio seedling growth in a lab-scale greenhouse, extending that direction from transparency alone to actively managing the spectral quality of the transmitted light.
Conventional perovskite films absorb blue light more strongly than red, so a continuous semi-transparent perovskite layer lets through light that's skewed toward red and near-infrared wavelengths, light that can hurt processes like chlorophyll synthesis and stomatal regulation. To avoid this, the team deposited the perovskite (AVA-MAPbI3) as discrete, isolated micrometer-scale islands rather than a continuous film, grown through a one-step, antisolvent-free process directly onto a mesoporous titanium dioxide (TiO2) scaffold. Each island forms a "cap" of perovskite above the surface with "roots" infiltrated into the porous TiO2 beneath it, maintaining an extended interface for charge extraction while leaving the uncovered regions between islands open for light to pass through largely unfiltered.
The resulting films reached about 28% average visible-light transmittance (tunable between roughly 24% and 39% depending on processing conditions) with a quasi-neutral color, rather than the reddish tint typical of continuous perovskite films. Test devices using a carbon electrode reached a 1.94% power conversion efficiency, while simulations indicate up to 4.50% should be achievable with an ideal transparent top electrode in place of carbon. Based on outdoor simulations for Catania, Italy, the team estimates such a device could generate around 116.4 kWh per square meter annually, enough to support energy-intensive greenhouse operations.
To test real-world compatibility, the researchers grew lettuce under an LED-simulated version of the light spectrum transmitted by their perovskite islands and compared it with a reference spectrum tailored for plant growth. After 30 days, they found no statistically significant differences in biomass, chlorophyll content, or leaf nitrogen and carbon levels between the two groups, suggesting the modified light spectrum didn't come at a cost to plant growth.
