Current Applied Physics, Vol.18, No.9, 1071-1079, 2018
Theoretical probe on modified organic dyes for high-performance dye-sensitised solar cell
We have proposed newly designed organic sensitizers, which could potentially be the best performing organic dyes for Dye Sensitised Solar Cell applications (DSSC). The designed sensitizers are derivatives of "Triphenylamine (TPA) - Tetrathienoacene (TTA) - Thiophene (T) - cyanoacrylic acid (A)" (TPA-TTAR-T-A) sensitizer. Our conclusions were based on calculations performed using Density Functional Theory (DFT) and Time Dependent Density Functional Theory (TD-DFT) methods, on various theoretical parameters of sensitizers that are pertinent to the Power Conversion Efficiency (PCE) of the solar cell. We strategically incorporated substitutions on the spacer located between the pi- bridge and the anchoring group, where the thiophene was inserted in previous study. We found that strengthening the electron withdrawing ability around thiophene spacer by fluorination and cyano substitution, and replacement of thiophene spacer with fluorinated and cyano substituted benzodithiophene complexes results in improved opto-electronic properties of the sensitizers. Thereby, we identified six new derivatives and for each derivative we have studied the parameters concerning short circuit current (J(sc)), such as molecular geometry, absorption spectrum, frontier molecular orbital patterns, electronic energy levels and excited state life time. Also, we have analysed the intramolecular charge transport characteristics of the designed dyes. By considering the overall computed parameters we were able to sort out two new sensitizers TPA-TTAR-2FT-A and TPA-TTAR-2F2CNBDT-A that delivered the needed characteristics and thereby brings in confidence that these sensitizers could challenge TPA-TTA-T-A as the best performing organic sensitizer.
Keywords:Organic sensitizer;Cyano substitution;Fluorination;Optoelectronic properties;Intramolecular charge transport