Efficiency enhancement of black dye-sensitized solar cells by newly synthesized D–π–A coadsorbents: a theoretical study

Abstract

In this work, using the DFT and TDDFT, we have theoretically studied the electronic and optical properties of the two recently synthesized coadsorbents Y1 and Y2, which were aimed to enhance the efficiency of the black dye-sensitized solar cells. To determine the solvatochromic shifts, both the implicit and mixed implicit-explicit models have been used. The connection between the solvatochromic shifts and the changes of dipole moments in the excitation process is discussed. The difference in excitation charge transfer is utilized to explain the experimentally observed difference in J sc for Y1 and Y2. Investigating the interactions of I 2 molecules in the electrolyte solution with the coadsorbents showed that with Y1 the recombination loss was weakened through decreasing the I 2 concentration near the TiO 2 surface, whereas with Y2 it was increased. As a result, the higher values of both J sc and V oc with Y1 coadsorbent explains its experimentally observed higher efficiency. The present study sheds light on how to design and engineer newer coadsorbents or organic dyes for higher efficiencies.

Stability of ruthenium/organic dye co-sensitized solar cells: a joint experimental and computational investigation

“…À ions far away from the semiconductor surface and to efficiently act as an anti-aggregation agent. 60 Despite the lower efficiencies, the trends of the measured parameters are consistent with those in the original paper. 19 The stability of the investigated devices was assessed with J-V measurements at 1/3 Sun (Table 1; Fig.…”

“…19 A key role in this regard is played by the butoxyl chains on the donor part of the molecule, that are able to keep the oxidized I 3 ions far from the semiconductor surface, and to efficiently act as an antiaggregation agent. 60 Despite the lower efficiencies the trend of the measured parameters are however consistent with the original paper. 19 Stability of the investigated devices was assessed with J-V measurements at ⅓ Sun.…”

“…This distortion from planarity does not prevent the conjugation extension over the whole donor-π spacer-acceptor (D-π-A) molecular structure, as recently observed by Azar and Payami. 60 This is clearly visible from the HOMO-LUMO plot of the Y1 and Y2 dyes (Figure 4). Similarly to related push-pull sensitizers the HOMO is localized on the donor and π-bridge moieties, while the LUMO is mainly located over the cyanoacrilic acceptor group.…”

Theoretical description of efficiency enhancement in DSSCs sensitized by newly synthesized heteroleptic Ru complexes

“…These blue shifts may also be explained by using the fact that the dipole moments in the excited states are smaller than their corresponding ground state vectors. 53 Recent studies on excitation energies have shown that for charge-transfer (CT) excitations, the TDDFT calculations may lead to errors of the order of some eV, [54][55][56] and the use of range-separated XC functionals has therefore been prescribed. 57 The diagnostic parameter Λ, which quantifies the charge-transfer character of excitations 53,57 and takes the values 0 ≤ Λ ≤ 1, are calculated for the dominant transitions of RD dyes and the results are listed in Table 3.…”

First-principles calculation of electronic energy level alignment at electrochemical interfaces

“…The description of detailed mechanisms involved at interfaces is not possible unless one uses computational methods. The density functional theory (DFT) 13,14 and its time-dependent extension (TDDFT) 15 have played significant roles in the design and engineering of electrochemical systems among which hydrogen evolution systems 16,17 and DSSC's [18][19][20][21][22] are the most common examples.…”