DFT/TD-DFT investigations on photovoltaic properties of N-Phenyl-N-(thiophen-2-yl)-1H-Pyrrol-2-amine and N,N-diphenylthiophen-2-amine based hexatriyne-thiophene Dye-sensitizers for DSSCs

Abstract

The optoelectronic and charge transfer properties of dyes containing N,N-diphenylthiophen-2-amine (NBBT) or N-phenyl-N-(thiophen-2-yl)-1H-pyrrol-2-amine (NTPA) as donor were computationally studied using density functional theory (DFT) and time dependent- density functional theory (TD-DFT) methods. Thiophene, fused thiophene and bridged thiophene derivatives were incorporated to extend the hexatriyne (LCC) π-linker (hexatriyne-thiophene π-linker) to examine the effect thiophene derivatives on the photovoltaic and optoelectronic properties of the designed dyes. The and values show that insertion of boron into hexatriyne-bridged thiophenes π-linker in NTPA-6 and NBBT-6 dyes traps some of the electrons to be transmitted to the acceptor moiety, which may account for low oscillation strengths observed for the dyes. This subsequently affects the light harvesting efficiency (LHE) and open current circuit (VOC), although, the fractions of electrons transmitted could probably take shorter time ( getting into the conduction band (CB) of semiconductor. The coupling constant (/VRP/) reveals influence on the rate of regeneration of the dyes. Also, slight lowering of EHOMO-ELUMO (ΔEg, eV) in respective NTPA dyes than NBBT dyes indicate more electrons are pushed by N-phenyl-N-(thiophen-2-yl)-1H-pyrrol-2-amine into the π-linker than N,N-diphenylthiophen-2-amine, and incorporation of fused thiophene and bridged thiophenes (except NTPA-6 and NBBT-6) improve the LHE dyes’s ability than PY-3N; thus hexatriyne-thiophene containing dyes exhibit favorable optoelectronic properties, making them good candidates for light absorption in dye sensitized solar cells (DSSCs).