A computational study on α-pyranylidene and α-thiopyranylidene as donor fragments in dye-sensitized solar cells

Mahajan, Dhruv and Mallik, Bhabani Shankar (2019) A computational study on α-pyranylidene and α-thiopyranylidene as donor fragments in dye-sensitized solar cells. Masters thesis, Indian institute of technology Hyderabad.

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Abstract

Dye-sensitized solar cells (DSSC’s) have slowly started to replace the conventional solar cells, and with the ongoing rate of depletion of inexhaustible resources, solar energy seems to be the most readily available renewable source of energy. DSSC has been under constant study from the past but still, work is being done to improve their efficiency and develop better metal-free organic dye sensitizers for use in dye-sensitized solar cells. Eight kinds of experimentally designed pyranylidene-based organic dyes for dye-sensitized solar cells were obtained. They were based on a donor-π-acceptor (D–π– A) structure, so-called push-pull systems, where α-pyranylidene and α-thiopyranylidene act as donor fragments and the cyanoacrylic acid act as acceptor fragment. A polymethine (-CH=)n chain is present acting as π-spacer. Various combinations of an ‘R’ group and π-spacer have been taken in each dye with a varying heteroatom as Oxygen or Sulphur. In this study, we focus on calculating the molecular and photoelectric properties of dyes using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) with a 6-31+G(d) basis set to provide with optimized ground state structures. Various other electronic properties like band gap, MO visualizations, vertical excitation energies, light harvesting energy (LHE), oscillator strength (f), etc. were found out. The effect of heteroatom on these dyes, conjugation and the presence of bulky group was also studied.

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