Extension of π-conjugation length along the Q_y axis of a chlorophyll a derivative for efficient dye-sensitized solar cells

摘要

A chlorophyll a derivative was synthesized and used for dye-sensitized solar cells with a solar energy-to-electricity conversion efficiency of 6.5%.rnChlorophylls (Chls) are the most abundant pigments in natural photosynthetic apparatus, playing roles of not only light-harvesting, but also electron- and energy-transferring. The photophysical and photochemical properties of Chls are tunable by structural modification on the tetrapyrrole macro-cycles. The Soret, Q_x and Q_y absorption bands are generated based on electron transitions between four molecular orbitals, i.e., HOMO-1. HOMO, LUMO and LUMO+ 1. For fully unsaturated tetrapyrrole structures (porphyrins), these Q bands are degenerate and shifted to a higher energy region. Porphyrins usually have intense Soret and weak Q bands, and this character regulates their light harvesting functions. In order to capture more solar energy, natural photosynthetic systems usually choose Chls possessing not porphyrin macro-cycles, but rather chlorin macrocycles as their antennae. Especially. Chl a species with relatively intense Q bands are commonly selected by higher plants during a long history of natural evolution.