AVA‐MAPbI ₃ Cap‐and‐Root Islands on Mesoporous TiO ₂ Toward Neutral‐Color Semi‐Transparent Perovskite Solar Cells in Agrivoltaics

Semi‐transparent perovskite solar cells offer a route to agrivoltaics, combining electricity generation with controlled light transmission for crop cultivation. However, conventional perovskite films preferentially absorb blue photons, producing redshifted transmitted spectra that can affect plant photophysiology. This work presents quasi‐neutral‐color semi‐transparent perovskite films based on AVA‐MAPbI ₃ islands rooted in mesoporous TiO ₂ (mp‐TiO ₂ ). This architecture localizes absorption within the islands while ensuring spectrally balanced, visually neutral transmitted light and efficient charge extraction via the extended perovskite/mp‐TiO ₂ interface. Films are fabricated through a one‐step, antisolvent‐free process where controlled de‐wetting and crystallization form islands anchored to the mp‐TiO ₂ scaffold. Island coverage and size are tuned via spin‐coating speed and annealing temperature. Using HTL‐free carbon‐based architecture as a testbed, perovskite coverage is identified as the main factor governing the transmittance‐efficiency trade‐off. Photocurrent scaling with coverage and conductive AFM measurements suggest that each island behaves as an independent photogeneration unit. Year‐long outdoor simulations at 37.3°N project that a device with an ideal transparent cathode can reach 4.50% efficiency and generate 116.38 kWh m ⁻²  year ⁻¹ , sufficient to power energy‐intensive greenhouses. Lettuce grown under an LED‐simulated perovskite spectrum showed uncompromised biomass, pigments, leaf nitrogen‐carbon content, and carbon/nitrogen ratio, supporting perovskite island‐based photovoltaics for agrivoltaic applications.