Insight into the Excited State Electronic and Structural Properties of the Organic Photovoltaic Donor Polymer Poly(thieno[3,4-b]thiophene benzodithiophene) by Means of ab Initio and Density Functional Theory

Abstract

Structural and electronic properties of the ground and lowest excited states of the electron-donor conjugated copolymer poly (thieno[3,4-b]thiophene benzodithiophene) (PTB1) are reported based on high-level theoretical investigations. PTB1 combined with phenyl-C 61butyric acid methyl ester (PCBM) results in a bulk heterojunction blend with promising properties for use in organic solar cells. The ab initio algebraic diagrammatic construction method to second order, ADC(2), was used to obtain benchmark data for excited state energies, oscillator strengths, and bond length alternation (BLA) analysis. Time dependent density functional theory (TDDFT) calculations using the exchange-correlation functionals PBE, B3LYP, BHandHLYP, CAM-B3LYP, and LC-wPBE were also performed and compared with ADC(2) calculations. It was shown that a minimum of 20% Hartree−Fock exchange in the functional is necessary to reproduce the major features of the ADC(2) results. Analysis of the BLA results indicates the possibility of exciton trapping by geometry relaxation occurring in the middle of the polymer chain. The corresponding exciton binding energy is about 0.4 eV. Charge distributions in the ground and lowest excited singlet state were analyzed as well. The natural population analysis (NPA) confirms the electronegative character of the benozodithiophene group and the corresponding positive one of the thienothiophene moiety leading to an alternant chain polarization of positive and negative charges. Electron density differences between the S 0 and S 1 states show a transfer of electron density from double bond regions to areas of single bonds, a feature which parallels nicely the lengthening of double bonds and shortening of single bonds in the S 1 state.

Synthesis and Photophysical and Anion‐Sensing Properties of Triarylborane‐Substituted Cross‐Conjugated and Conjugated Thienothiophenes

“…Minima were verified by analysis of the harmonic vibrational frequencies using analytical second derivatives. TD‐DFT calculations including the solvent effect (CPCM) were realized by using coulomb‐attenuating density functional theory (CAM‐TD‐B3LYP) with the 6‐31++G(d,p) basis set to calculate the lowest singlet–singlet vertical excitations due to the convincing performance of CAM‐B3LYP in the predictions of excitation energies . NStates of 50 for singlets were calculated to obtain absorption bands.…”

Origin of the Excited-State Absorption Spectrum of Polythiophene

“…These authors performed nonlinear-response time-dependent density functional theory (TD-DFT) calculations using the Coulomb-attenuated Becke 3-Parameter (Exchange), Lee, Yang, and Parr (CAM-B3LYP) functional on oligofluorenes ranging from the dimer to heptamer, showing that the NIR ESA band is due to a dominant S 1 → S 5 transition. The CAM-B3LYP functional has been employed in other recent computational studies of conjugated oligomers, showing high-level performance in predicting the physical and chemical properties of these systems. − In this study, the electronic properties of the S 1 excited state of oligothiophenes are investigated using nonlinear-response TD-DFT. The computational methods used are shown in the Supporting Information (SI).…”

Organoboron copolymers containing thienothiophene and selenophenothiophene analogues: optical, electrochemical and fluoride sensing properties

“…27 TD-DFT calculations with solvent effect (CPCM) 28 were conducted on polymer segments at coulomb-attenuating density functional theory (CAM-TD-B3LYP) 29 level with 6-311++G (d,p) basis set to obtain the lowest singlet-singlet vertical excitations owing to the good performance of CAM-B3LYP in the calculations of excitation energies. 30 Absorption bands were collected for singlets with N states of 50. While visualization of MOs with an isosurface value of 0.04 au was accomplished with GaussView 5.0, absorption and emission spectra were produced with GaussSum 3.0.…”