Molecular design and synthesis of acetohydrazonoyl cyanide structures as efficient dye-sensitized solar cells with enhancement of the performance of the standard N-719 dye upon co-sensitization

Abstract

Four novel acetohydrazonoyl cyanide compounds (5–8) with a triphenylamine moiety as an electron donor for use in dye-sensitized solar cells (DSSCs) have been designed and synthesized. The target molecules and their intermediates were well characterized using various spectral techniques. Their absorption spectra and electrochemical and photovoltaic properties are extensively investigated and compared with N-719 dye. The photovoltaic efficiency of these new dyes under AM1.5 ranges from 1.91% to 5.17% without the use of any additive. Compound 8 achieved the highest photovoltaic conversion efficiency (PCE, η = 5.17%) among the existing dyes due to the high values of the photocurrent (JSC = 13.66 mA cm−2) and photovoltage (VOC = 647 mV). Due to the good results shown by compound 8, the compound was used as a co-sensitizer along with the N-719 dye to improve its properties and raise its efficiency. The results showed that using (0.2 mM of compound 8 + 0.2 mM of N-719) improved the performance of the fabricated cell (PCE, η = 8.63%) with the enhancement in both VOC (682 mV) and JSC (20.39 mA cm−2) compared to the cell fabricated with N-719 alone (PCE, η = 6.23%, VOC = 623 mV, JSC = 16.48 mA cm−2). Furthermore, electronic excitations simulated using time-dependent DFT agreed well with experimentally obtained sensitizer results, indicating that the exchange-correlation function and basis set used to predict the spectra of the co-sensitizers are quite appropriate for the calculations. In conclusion, the results showed the potential of simple organic co-sensitizers in the development of efficient DSSCs.