Computational study of linear carbon chain based organic dyes for dye sensitized solar cells

Spectroscopic, electronic and electron injection properties of a new class of linear carbon chain (LCC) based organic dyes have been investigated, by means of density functional theory (DFT) and time-dependent density functional theory (TDDFT), for application in dye-sensitized solar cells (DSSCs). The photophysical properties of LCC-based dyes are tuned by changing the length of the linear carbon chain; UV/VIS absorption is red-shifted with increasing LCC length whereas oscillator strength and electron injection properties are reduced. Excellent nonlinear optical properties are predicted in particular for PY-N4 and PY-S4 dyes in the planar conformation. Results indicate that a LCC-bridge produces better results compared to benzene and thiophene bridges. Simulations of I^--Dye@(TiO₂)₁₄ and Dye@(TiO₂)₁₄ anatase complexes indicate that designed dyes inject electrons efficiently into the TiO₂ surface and can be regenerated by electron transfer from the electrolyte. Superior properties in terms of efficiency are shown by compounds with a pyrrole ring as the donor group and PY-3N is expected to be a promising candidate for applications, however all the investigated dyes could provide a good performance in solar energy conversion. Our study demonstrates that computational design can provide a significant contribution to experimental work; we expect this study will contribute to future developments to identify new and highly efficient sensitizers.