Theoretical Analysis on Heteroleptic Cu(I)-Based Complexes for Dye-Sensitized Solar Cells: Effect of Anchors on Electronic Structure, Spectrum, Excitation, and Intramolecular and Interfacial Electron Transfer

Abstract

Two groups of heteroleptic Cu(I)-based dyes were designed and theoretically investigated by density functional theory (DFT) and time-dependent DFT (TD-DFT) methods. Different anchors were integrated into the dye skeleton to shed light on how the type of anchor influenced the electronic structure, absorption spectrum, electron excitation, and intramolecular and interfacial electron transfer of dyes. The results indicated that, compared with other dyes, the dyes with cyanoacrylic acid and nitric acid exhibited more appropriate electron distributions in frontier molecular orbitals (FMOs), lower HOMO (the highest occupied molecular orbital) –LUMO (the lowest unoccupied molecular orbital) energy gaps, broader absorption spectral ranges as well as improved spectral characteristics in the near-infrared region and better intramolecular electron transfer (IET) characteristics with more electrons transferred to longer distances, but smaller orbital overlap. Among all the studied Cu(I)-based dyes, B1 and P1 (with cyanoacrylic acid anchoring group) exhibited the best interface electronic structure parameters with a relatively short electron injection time (τinj) and large dipole moment (μnormal), which would have a positive effect on the open-circuit photovoltage (Voc) and short-circuit current density (Jsc), resulting in high power conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs). Our findings are expected to provide a new insight into the designing and screening of high-performance dyes for DSSCs.

Heteroleptic Cu(i) bis-diimine complexes as sensitizers in dye-sensitized solar cells (DSSCs): on some factors affecting intramolecular charge transfer

“…43 (2) Metal to anchoring ligand involving the carboxylic group (MLCT). This is also good for charge separation and injection, as has been noted in systems 44 similar to the ones studied here. In these, 44 the first absorption band was found to have several typical metal-to-ligand charge transfer (MLCT) transitions (HOMOÀ2 -LUMO/LUMO+1) and a ligand-to-ligand charge transfer (LLCT) transition (HOMOÀ1 -LUMO+1), from the electron donor groups to the electron acceptor groups, which could form a favourable charge-separated state to hinder electron recombination.…”

DFT and TD‐DFT Study on Azobenzene‐Based Dye Covalently Attached to Silane Coupling Agents: Toward Dye‐Sensitized TiO2 Catalyst and Dye‐Sensitized Solar Cell Applications

“…J sc is also affected by the regeneration efficiency of the oxidized dye ( η reg ). The driving force of dye regeneration (▵ G reg ) plays a role in the determination of η reg and is expressed by the following equation: [14,19] …”

“…J sc is also affected by the regeneration efficiency of the oxidized dye (η reg ). The driving force of dye regeneration (~G reg ) plays a role in the determination of η reg and is expressed by the following equation: [14,19] DG reg ¼ E redox À E dye , (5) where E redox denotes the redox potential of I À /I 3 À (À 4.8 eV) in an electrolyte solution. [7a,12,15] For E-MPDNA-OTES,~G reg of A2 was lower than that of A1.…”

Spectroscopic Behaviour of Copper(II) Complexes Containing 2-Hydroxyphenones

“…Knowledge of the MOs involved in excitations can identify the type of excitation such as metal-to-ligand chargetransfer (MLCT) [11,13,14], ligand-to-metal charge-transfer (LMCT), ILCT (intra-ligand charge transfer) [12], and ligand-to-ligand charge transfer (LLCT) bands [9]. DFT calculated properties to evaluate the dye performance in DSSCs, such as charge transfer characteristics, light harvesting efficiency (LHE), the excited-state lifetime (τ), driving force of electron injection (∆G inject ) and dye regeneration (∆G regenerate ), are often reported [5,11,[13][14][15][16][17]. DFT calculations can assist in the design of complexes with improved photo conversion.…”