Effect of Seleno-Thiophene π-Linkers on Electronic and Photovoltaic Properties of Boro-Phenothiazine Donors for DSSCs Application: TD-DFT and DFT Methods

In this paper, a theoretical study on the electronic and photovoltaic properties are presented for eleven dye-sensitizers and their respective dye-TiO2 couples, using DFT and TD-DFT methods. The dye-sensitizers are of the form D-pi-A dyes, with boro-phenothiazine derivatives as electron donors, pi-conjugated bridge is based on the thiophene/selenophene and 2-cyanoacrylic acid as the electron acceptor unit. The global descriptors and photovoltaic properties of the dye-sensitizers are evaluated and results reveal those dyes with CH3-, CH3O-, and benzyl-substituents on the boro-phenothiazine donor have shorter r2 bond lengths, increase in theta 2 planarity, lower band gap, enhance Voc and strong electron injecting abilities. Also, changing of thiophene pi-linker to thieno[3,2-b]thiophene analogues shift lambda(max) to longer wavelength, shorten r2 and slightly increase theta 2 planarity. All the dye-sensitizers are viable candidates for application as sensitizers in DSSCs, and the auxiliary donor groups, as well as conjugated pi-linkers finetune the electronic, optical and photovoltaic properties for better performance of the dye-sensitizers in improving DSSC.