OPTOELECTRONIC PROPERTIES OF TRIPHENYLAMINE BASED DYES FOR SOLAR CELL APPLICATIONS. A DFT STUDY

Abstract: Dye-sensitized solar cells (DSSCs) based on triphenylamine (TPA) as a donor group linked with the acceptor cyanoacrylic acid electron acceptor by 2,2’-bithiophene as π-bridged (D-π-A) has been investigated by Density Functional Theory (DFT) at the B3LYP/6-311G(d,p) level of theory, to establish the conformational orientation of cyanoacrylic acid group as well as evaluate the effect of planarizing the 2,2’-bithiophene unit in position 3 and 3’ by electron withdrawing or donor groups on the electronic structure properties of ground and doping(n,p) states. Also, the Time Dependent Density Functional Theory (TD-DFT) at the CPCM-TD-CAM-B3LYP//CAM-B3LYP/6-311G(d,p) level of theory were selected to modulate the electronic absorption spectra and charge-transfer capabilities of the molecules analyzed in the present work. The results indicate that adding an auxiliary donor or withdrawing group to the 2,2’-bithiophene in the (D-π-A) arrangement allow to modify the LUMO’s energy of the dyes, while the HOMO's energy is slightly affected.

摘要：以三苯胺（triphenylamine, TPA）为给体基团，通过2,2'-联噻吩（2,2’-bithiophene）作为π桥，与受体氰基丙烯酸（cyanoacrylic acid）电子受体相连的D-π-A型染料敏化太阳能电池（Dye-sensitized solar cells, DSSCs），本研究采用密度泛函理论（Density Functional Theory, DFT）在B3LYP/6-311G(d,p)理论水平下开展计算研究，旨在明确氰基丙烯酸基团的构象取向，并评估在2,2'-联噻吩单元的3、3’位引入吸电子或给电子基团以平面化该单元时，对基态以及掺杂（n型、p型）态电子结构性质的影响。此外，本研究选取基于CPCM-TD-CAM-B3LYP//CAM-B3LYP/6-311G(d,p)理论水平的含时密度泛函理论（Time Dependent Density Functional Theory, TD-DFT）方法，对本文所分析分子的电子吸收光谱与电荷转移能力进行模拟分析。结果表明，在D-π-A结构的2,2'-联噻吩上引入辅助给电子或吸电子基团，可改变染料的最低未占据分子轨道（Lowest Unoccupied Molecular Orbital, LUMO）能级，而最高占据分子轨道（Highest Occupied Molecular Orbital, HOMO）能级仅受轻微影响。