Influence Of Donor Configurations On Photophysical, Electrochemical, And Photovoltaic Performances In D-Pi-A Organic Sensitizers

To optimize light harvesting capabilities, one or two indoline units are introduced as additional donors into the traditional D-pi-A model and constructed D-D-pi-A sensitizers, CQ(2) and CQ(3). Absorption spectra and cyclic voltammetry are performed to evaluate the influence of different donor configurations on photophysical and electrochemical properties as well as photovoltaic performances. Incorporating the strong electron-donating indoline unit as an additional donor in CQ(2) and CQ(3) brings several characteristics, such as improving the visible light-harvesting capability and strengthening the intramolecular charge transfer (ICT) process, as well as positively shifting the HOMO energy level. Moreover, CQ(3) is more dependent upon coadsorbents. Upon coadsorption with 5 mM CDCA, an obvious increment of more than 160% in Jsc is achieved for CQ(3), from 4.26 (without CDCA) to 11.15 rnA cm(-2) (5 mM CDCA). From photovoltaic performances, dye CQ(2) with one additional indoline unit is preferable. Among the three dyes, CQ(2) containing one indoline unit shows the highest conversion efficiency of 6.38%, with the photovoltaic parameters of J = 11.33 mA cm-2, 1/0c = 792 mV, and ff = 0.71 under 100 mW cm-2 simulated AM 1.5 G solar irradiation. It is indicative that the incorporation of the additional donor indoline on the framework of the triphenylamine core of CQ1 is beneficial to the optimization of photovoltaic performances. However, the incorporated multidonor units as additional donors in D-D-pi-A type sensitizers can bring deteriorating intermolecular interactions between crowded donor units.