Bands, Beets & Berries: A Quantum Study of Natural Dyes for Solar Cells.

Dye-sensitised solar cells (DSSCs) offer a sustainable alternative to silicon-based photovoltaics, but widespread adoption is hindered by the cost and scarcity of mainstream dyes. This study investigates the viability of a selection of natural pigments; pelargonidin, betanin, lutein, quercetin, and copper chlorophyllin A as low-cost, sustainable sensitisers for DSSCs. Using density functional theory (DFT) and time-dependent DFT (TD-DFT), the electronic structures, UV-Vis absorption profiles, and electrostatic potential (ESP) maps of each dye were evaluated and compared to the benchmark N3 dye. Copper chlorophyllin A emerged as the most promising candidate, exhibiting strong visible light absorption, favourable frontier orbital alignment, and robust anchoring potential to TiO₂. Quercetin also showed potential due to favourable electrostatic characteristics and photostability, though its absorption is UV-weighted. The findings support the feasibility of locally sourced, natural dyes for DSSC application, and suggest co-sensitisation as a strategy to broaden absorption and improve performance.