Does the position of the electron-donating nitrogen atom in the ring system influence the efficiency of a dye-sensitized solar cell? A computational study

Abstract

We have reported a number of new metal-free organic dyes (2-6) that have cyclic asymmetric benzotripyrrole derivatives as donor groups with peripheral nitrogen atoms in the ring, fluorine and thiophene groups as π-spacers, and a cyanoacrylic acid acceptor group. Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations were employed to examine the influence of the position of the donor nitrogen atom and π-conjugation on solar cell performance. The calculated electron-injection driving force (ΔG inject), electron-regeneration driving force (ΔG regen), light-harvesting efficiency (LHE), dipole moment (μ normal), and number of electrons transferred (∆q) indicate that dyes 3, 4, and 6 have significantly higher efficiencies than reference dye 1, which exhibits high efficiency. We also extended our comparison to some other reported dyes, 7-9, which have a donor nitrogen atom in the middle of the ring system. The computed results suggest that dye 6 possesses a higher incident photon to current conversion efficiency (IPCE) than reported dyes 7-9. Thus, the use of donor groups with peripheral nitrogen atoms appears to lead to more efficient dyes than those in which the nitrogen atom is present in the middle of the donor ring system. Graphical Abstract The locations of the nitrogen atoms in the donor groups in the designed dye molecules have an important influence on DSSC efficiency.

Effect of Electron-Withdrawing/-Donating Groups on the Sensitizing Action of the Novel Organic Dye “3-(5-(4-(Diphenylamino)styryl)thiophen-2-yl)-2-cyanoacrylic Acid” for N-Type Dye-Sensitized Solar Cells: A Theoretical Study

“…It can also be seen from Figure 1 that all the different dyes considered in this work have their LUMO energies above the CB edge of TiO 2 (see Figure 1), thus allowing a favorable interfacial electron injection from the excited dyes to the CB of TiO 2 . Furthermore, we found that for all the considered dyes, the HOMO lies below the iodide redox potential (−4.58 eV) 32,78 (see Figure 1). All EW substituents lower both E HOMO and E LUMO , in fact more significantly for the donor substituents, whereas the opposite is true for the ED substituents.…”

“…However, the regeneration of the dye reflected by the redox mediator Δ G regen also influences J SC . Higher negative values of the Δ G regen will have an adverse effect on the J SC with respect to the efficiency of the dye . Δ G regen values higher (more toward zero) than −0.36 eV ( D5 , Table ) cause a higher J SC than the one for the D5 dye.…”

A DFT study to probe homo-conjugated norbornylogous bridged spacers in dye-sensitized solar cells: an approach to suppressing agglomeration of dye molecules

“…7 However, metal base dyes have demerits like leaching from the semiconductor surface and heavy metal environmental hazards as well as higher cost and limited resources. 39 Organic dyes are alternatives to overcome such problems.…”

“…It is suggested that for efficient electron injection into anode the HOMO should be localized over the D-S part and the lowest unoccupied molecular orbital (LUMO) of the dye should be localized near the anchoring group and above the conduction band edge of the semiconductor electrode (here TiO 2 ). 39 The HOMO-LUMO pictures of spacer group 1-6 and 6-D are given in Fig. 6 suggests that for all the systems HOMO orbitals are localized over D-S-A part whereas the LUMO orbitals are localized over the S-A part.…”

The influence of noncovalent interactions in metal‐free organic dye molecules to augment the efficiency of dye sensitized solar cells: A computational study

“…The experimentally reported maximum absorption spectra (λ max ) are compared with the λ max obtained at different DFT functionals. The reported dyes ( 1 , 3 , 5 , 7 , and 9 ) were optimized with B3LYP/6–31G* level of theory and the λ max values were calculated using different DFT functionals with larger basis set: B3LYP/6‐31 + G*, M062X/6‐31 + G*, ωB97XD/6‐31 + G*, bp86/6‐31 + G*, PBE0/6‐31 + G* MPW1K/6‐31 + G*, and CAM‐B3LYP/6‐31 + G* (Table ) . The calculated results suggest that the ωB97XD/6 − 31 + G* method is in better agreement with the experiment λ max than other functionals and hence it is used for further studies.…”