TD-DFT and DFT Investigation on Electrons Transporting Efficiency of 2-Cyano-2-Pyran-4-Ylidene-Acetic Acid and 2-Cyanoprop-2-Enoic Acid as Acceptors for Thiophene-Based p-Linkers Dye-Sensitized Solar Cells

Great attention is being shifted to Dye-sensitized solar cells because of their structural and electronic tunability, high performance, and low cost compared to conservative photovoltaic devices. In this work, B3LYP/6-31G** level of theory was used to study the molecular architecture of the donor-pi-acceptor (D-pi-A) type. This architecture contains a series of dyes with the 2-cyano-2-pyran-4-ylidene-acetic acid (PLTP-dye) and 2-cyanoprop-2-enoic acid (CLTP-dye) units as acceptors; donor groups and thiophene-based pi-linkers. The molecular and electronic properties, light harvesting efficiency, open circuit voltage (V-OC), injection force (Delta G(inject)), regeneration force (Delta G(regen)) and excitation state lifetime (tau(esl)) were calculated. CLTP-dyes showed lower band gap, chemical hardness (eta), chemical potential (mu), higher electrophilicity (omega) and electron denoting power (omega(-)) than the corresponding PLTP-dyes. The omega(-) demonstrated that PLTP-1, PLTP-2 and PLTP-3, CLTP-1, CLTP-2 and CLTP-3 should readily push electrons to the pi-linker, which can lead to high intra-molecular charge transfer and photocurrent for the dyes. The Voc and Delta G(inject) parameters favoured the CLTP-dyes over corresponding PLTP-dyes, and also dyes with the N,N-diphenylaniline donor have higher Voc, Delta G(inject) values and longer wavelengths (lambda(max)) than the dyes with carbazole unit (N,N-diphenylaniline dyes > Carbazole dyes) in accordance with the calculated omega(-), although all the dyes have good regeneration and injection abilities.