Theoretical Investigation on Copper(I) Complexes Featuring a Phosphonic Acid Anchor with Asymmetric Ligands for DSSC

A series of heteroleptic copper(I) complexes featuring a phosphonic acid anchor with asymmetric ligands has been studied using density functional theory (DFT) and time-dependent DFT (TD-DFT). Results showed that the absorption spectra of all copper(I) complexes covered the visible light region with typical metal-to-ligand charge transfer characteristics. The modification of functionalized asymmetric ligands by introducing phenyl, anisole, N,N-diethyl-4-vinylaniline, and bromobenzene groups can reduce the energy gap (Delta H-L), form an effective charge-separated state, and lead to red-shifted absorption within the 350-650 nm range compared to the reference complex. The copper(I) complexes with functionalized N,N-diethyl-4-vinylaniline ligands displayed the smallest Delta H-E and highest light-harvesting efficiency (LHE), exhibiting excellent light-harvesting capabilities. The introduction of isoquinoline ligands increased the excited singlet state lifetimes, the number of transferred electrons, and electron transfer distances. The electron injection time and driving force revealed efficient interfacial electron injection and regeneration of oxidized dyes. The photoelectronic properties of copper(I) complexes featuring a pyridine ring with asymmetric ancillary ligands were superior to those of the reference complex. These copper(I) complexes exhibited desirable electronic and spectral characteristics for future DSSC applications.