Density Functional Theory Study on the Electronic Structures of Oxadiazole Based Dyes as Photosensitizer for Dye Sensitized Solar Cells

Umer Mehmood,Khalil Harrabi,Ibnelwaleed A Hussein,Shakeel Ahmed

doi:10.1155/2015/286730

Abstract

The molecular structures and UV-visible absorption spectra of complex photosensitizers comprising oxadiazole isomers as theπ-bridges were analyzed by density functional theory (DFT) and time-dependent DFT. The ground state and excited state oxidation potentials, HOMOs and LUMOs energy levels, and electron injection from the dyes to semiconductor TiO2have been computed in vacuum here. The results show that all of the dyes may potentially be good photosensitizers in DSSC. To justify the simulation basis, N3 dye was also simulated under the similar conditions. Simulated absorption spectrum, HOMO, LUMO, and band gap values of N3 were compared with the experimental values. We also computed the electronic structure properties and absorption spectra of dye/(TiO2)8systems to elucidate the electron injection efficiency at the interface. This work is expected to give proper orientation for experimental synthesis.

Highlights

The conversion of photoenergy into electrical energy is generally considered as the most potential way to resolve the world energy crisis, owing to its huge reserves
While oxadiazole isomers were introduced as π-conjugation to bridge the donor-acceptor systems, a double bond and a thiophene unit were introduced to the pi-conjugation system for the fine tuning of molecular planar configurations and to broaden the absorption spectra
Four photosensitizers based on oxadiazole isomers as piconjugated spacer were designed and simulated using density functional theory (DFT)/TD-DFT

Summary

Introduction

The conversion of photoenergy into electrical energy is generally considered as the most potential way to resolve the world energy crisis, owing to its huge reserves. The need of highly purified silicon, use of toxic chemicals in their manufacture, and the high cost have restricted their worldwide use These constraints encouraged the search for low cost and environmentally friendly solar cells. Metal-free organic photosensitizers are preferred over ruthenium based sensitizers because of their low cost and good transport properties. The oxadiazole derivatives are considered as the most efficient electron transport materials owing to their good thermal and chemical stabilities and high quantum yield [14]. DFT/TD-DFT is an effective tool in investigating the ground and excited state properties of photosensitizer complexes as compared to other high level quantum approaches because the computed orbitals are suitable for the typical MO-theoretical analyses and interpretations [19]. Many theoreticians have successfully applied this approach in the designing of photosensitizers [20,21,22,23,24,25]

Theoretical Background

Computational Details

Results and Discussion

Conclusion