Organic dyes with imidazole derivatives as auxiliary donors for dye-sensitized solar cells: Experimental and theoretical investigation

In order to study the influence of different imidazole derivatives in triphenylamine-based organic dyes, two different imidazole derivatives are introduced into the phenyl ring of the triphenylamine core, coded as CD-4 and CD-6 , respectively. Their photophysical, electrochemical properties and the performances of the corresponding dye-sensitized solar cells (DSSCs) are further investigated. Due to the better molar extinction coefficient, quantum efficiency (QE) and longer lifetime of excited electron, the DSSC based on CD-4 has the higher overall conversion efficiencies as 4.11% than that of CD-6 as 1.51% under full sunlight (AM 1.5G, 100  mW cm −2 ) irradiation. Density functional theory (DFT) and time dependent density functional theory (TD-DFT) calculations were carried out to study the ground state structures, the electronic structures and the optical properties of the two dyes. The simulated UV–vis absorption spectra for the two dyes are in excellent agreement with the experimental results.