Theoretical study of the effect of π-linkers on triarylamine-based p-type D-π-A sensitiser

ABSTRACT

Six p-type dyes with D-π-A structures were designed, and their molecular structures and electronic properties were studied by the density functional theory and the time-dependent density functional theory. Thiophene, thiophene[3,4-c][1,2,5] thiadiazide and thiazole[5,4-d]thiazole in combination with dithieno[3,2-b:2',3'-d]thiophene (s-DTT) were introduced into the newly designed dyes to extend π-linkers. The results showed that the enhanced conjugation of π-linkers increases the coplanarity and decreases HOMO–LUMO gap of the dyes. The absorption spectra of dyes 1–6 are obviously red-shifted. Compared to those of QT-1, the spectra of dyes 3 and 6 are red-shifted by 128 and 154 nm, and the oscillator strengths are improved by 70% and 71%, respectively. Dyes 3 and 6 have not only the strongest absorption peaks, but also a large absorption area in the range of 400–900 nm. This guarantees them stronger light absorptions. They also have the maximum charge separation degree (t), resulting a reduced hole recombination. Furthermore, the light harvesting efficiency (LHE), hole injection power (ΔG_inj), dye renewable power (ΔG_reg) and charge recombination force (ΔG_CR) of dyes 3 and 6 are superior to those of other dyes. In addition, the bromine substitution can effectively promote the red-shift of the absorption spectra.

KEYWORDS:

• P-type dyes
• π-linkers
• DFT/TDDFT
• absorption spectrum
• light harvesting

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

LX Kong thanks the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD) for partially supporting this work.