PBE-DFT theoretical study of organic photovoltaic materials based on thiophene with 1D and 2D periodic boundary conditions

摘要

Conjugated organic systems such as thiophene are interesting topics in the field of organic solar cells. We theoretically investigate pi-conjugated polymers constituted by n units (n = 1-11) based on the thiophene (Tn) molecule. The computations of the geometries and electronic structures of these compounds are performed using the density functional theory (DFT) at the 6-31 G(d, p) level of theory and the Perdew-Burke-Eenzerhof (PBE) formulation of the generalized gradient approximation with periodic boundary conditions (PBCs) in one (1D) and two (2D) dimensions. Moreover, the electronic properties (HOCO, LUCO, E (gap), V (oc), and V (bi)) are determined from 1D and 2D PBC to understand the effect of the number of rings in polythiophene. The absorption properties-excitation energies (E (ex)), the maximal absorption wavelength (lambda(max)), oscillator strengths, and light harvesting-efficiency are studied using the time-dependent DFT method. Our studies show that changing the number of thiophene units can effectively modulate the electronic and optical properties. On the other hand, our work demonstrates the efficiency of theoretical calculation in the PBCs.