Influence of the Donor Size in D−π–A Organic Dyes for Dye-Sensitized Solar Cells

Abstract

We report two new molecularly engineered push-pull dyes, i.e., YA421 and YA422, based on substituted quinoxaline as a π-conjugating linker and bulky-indoline moiety as donor and compared with reported IQ4 dye. Benefitting from increased steric hindrance with the introduction of bis(2,4-dihexyloxy)benzene substitution on the quinoxaline, the electron recombination between redox electrolyte and the TiO2 surface is reduced, especially in redox electrolyte employing Co(II/III) complexes as redox shuttles. It was found that the open circuit photovoltages of IQ4, YA421, and YA422 devices with cobalt-based electrolyte are higher than those with iodide/triiodide electrolyte by 34, 62, and 135 mV, respectively. Moreover, the cells employing graphene nanoplatelets on top of gold spattered film as a counter electrode (CE) show lower charge-transfer resistance compared to platinum as a CE. Consequently, YA422 devices deliver the best power conversion efficiency due to higher fill factor, reaching 10.65% at AM 1.5 simulated sunlight. Electrochemical impedance spectroscopy and transient absorption spectroscopy analysis were performed to understand the electrolyte influence on the device performances with different counter electrode materials and donor structures of donor-π-acceptor dyes. Laser flash photolysis experiments indicate that even though the dye regeneration of YA422 is slower than that of the other two dyes, the slower back electron transfer of YA422 contributes to the higher device performance.

Optimizing CuO p-type dye-sensitized solar cells by using a comprehensive electrochemical impedance spectroscopic study

“…To this end, our work provides a guideline for the development of photocathodes for DSSCs. EIS characterization of n-type DSSCs is a well-established technique, [9][10][11][12][13][14] but detailed EIS investigations on p-type DSSCs are surprisingly scarce. Wu et al were among the first to apply EIS to p-type DSSCs and to interpret the obtained parameters.…”

To pump the thermal energy from the dark world

“…[22][23][24][25][26][27][28] GaAs thin-film cell, with a bandgap of 1.4 eV, demonstrates a high efficiency of 28%. [29,30] Dye-sensitized solar cells [31,32] and organic solar cells [33,34] also develop quickly. Among all, multi-junction solar cells currently own the highest efficiency.…”

Insertion of a naphthalenediimide unit in a metal-free donor–acceptor organic sensitizer for efficiency enhancement of a dye-sensitized solar cell

“…It is worth noting that metal-free organic dyes are now very competitive with the metalcontaining sensitizers and have afforded remarkably high cell efficiencies (>12%) [9][10][11][12][13][14][15][16]. Of these reports comprising metal-free organic dyes, the highest PCE over 14% has been reported by K. Kakiage et al using collaborative sensitization [17], thus demonstrating the potential of organic sensitizers.…”