Theoretical Design of Benzoselenadiazole Based Organic Donor Molecules for Solar Cell Applications

Abstract

A series of organic donor molecules of the donor-acceptor-donor (D1-p-A-p-D2) type containing triphenylamine (TPA) and thiophene (Th) as donor units and 4,7-di(thiophen-2-yl)benzo[c][1,2,5] thiadiazole (DBT), 4,7-di(thiophen-2-yl)benzo[c][1,2,5] oxodiazole (DBO) and 4,7-di(thiophen-2-yl)benzo[c][1,2,5] selenadiazole (DBSe) as acceptor fragments with vinyl moiety as p-bridge and nitro unit (-NO 2 ) as electron withdrawing end cap have been designed for organic solar cell applications. The designed molecules are analyzed using density functional theory (DFT) and time dependent-DFT (TD-DFT) calculations at PBE0/6-31G(d,p) level. The effect of heteroatom substitutions from sulphur in central DBT unit with oxygen in DBO and selenium in DBSe were studied. The geometrical and electronic basis for selecting the number of Thn (n = 1-5) units as donor fragments has been elucidated in detail. The designed donors are screened against [6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM), bisPCBM, and PC70BM as reference acceptors. The ordering of frontier molecular orbitals (FMOs) of the designed donors and those of the fullerene acceptors has been compared to develop more compatible organic donor molecule to be used in tandem with these acceptors. Results show that a minimum of three thiophene units are necessary for an optimum alignment of FMOs with those of PCBM derivatives. The hetero substitution of S by Se alters the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels and there by reduces the band gap to 1.99 eV with wide absorption range from ultraviolet to infrared regions.

Outstanding NLO response of K3O@thia[n]circulenes; a DFT and molecular dynamics perspective

“…This specific type of range-separated functional yields highly accurate results for NLO parameters (α o and β o ) comparable to the most precise CCSD(T) benchmark [60] and other previous reports [61,62]. Considering this remarkable accuracy, CAM-B3LYP with the 6-31+G(d) level of theory has been selected for calculating the polarizability (α o ) and first hyperpolarizability (β o ) values to estimate the NLO response of complexes (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18). The behavior of occupied and unoccupied molecular orbitals is briefly explained by Pople's 6-31+G(d) basis set [63].…”

“…Additionally, thia [8]circulenes (18) has central octagon formed by the fusion of eight benzene rings. The carbon atoms at the peripheral of the fused rings are substituted with multiple sulfur atoms to obtained eighteen thia[7&8]circulenes (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18). All thia[7&8]circulenes (1-18) have planer geometries except 16 and 17 those have bowel shaped geometries.…”

“…Several reports have substantiated these properties through the comparison of computational results with experimental data [49][50][51][52][53][54][55]. Frequency analysis is performed after optimization which justified true minimizations of all K 3 O doped thia(n = 7&8)circulenes (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18). All the complexes have positive frequencies with the absence of any negative frequencies and confirmed the stable geometric structures.…”

“…GaussView 5.0 [47], builder is used for visualization of results of K 3 O doped circulenes (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18). Gaussian 09 program [48] is used for execution of simulations of all doped circulenes.…”

“…Chemists have given great attention to polycyclic thia[n]circulenes because of their applications in organic photovoltaics, hydrogen adsorption efficiency and organic field effect transistors etc [1,2]. Since last few years, scientists have observed an extra ordinary semiconducting nature and charge carrier mobilities of thia [n] circulenes [3][4][5] and it is believed that thia[n]circulenes can be used for the manufacturing and modelling of nonlinear optical (NLO) materials [6].…”