Novel and Stable D-A-pi-A Dyes for Efficient Solid-State Dye-Sensitized Solar Cells

Two novel organic donor-acceptor-pi-acceptor sensitizers, W7 and W8, have been applied in efficient solid-state dye-sensitized solar cells (ssDSSCs). Using 2,2', 7,7'-tetrakis(N, N-di-p-methoxyphenylamine) 9,9'-spirobifluorene (Spiro-OMeTAD) as hole-transport material (HTM), an excellent power conversion efficiency of 6.9% was recorded for W7, together with an excellent photocurrent of 10.51 mA cm(-2) and a high open-circuit voltage of 880 mV under standard AM 1.5 G illumination (100 mW cm(-2)). The solid-state solar cells based on W8 showed an efficiency of 5.2%, with a good photocurrent of 9.55 mA cm(-2) and an open-circuit voltage of 870 mV. Compared to that of the well-known WS2 sensitizer, the results show that the performance of the ssDSSC devices can be significantly improved by introducing triphenylamine moiety into their structure. In addition, results of photoinduced absorption spectroscopy show efficient dye regeneration for W7-and W8-based devices. A higher hole conductivity of the W7/HTM and W8/HTM layers compared to that of the WS2/HTM layer was observed, indicating an efficient charge transfer at the interfaces. The results obtained offer insights into the design of reliable and highly efficient ssDSSCs for large-scale applications

Molecular Engineering of D–D−π–A-Based Organic Sensitizers for Enhanced Dye-Sensitized Solar Cell Performance

A series of molecularly engineered and novel dyes WS1, WS2, WS3, and WS4, based on the D35 donor, 1-(4-hexylphenyl)-2,5-di­(thiophen-2-yl)-1<i>H</i>-pyrrole and 4-(4-hexylphenyl)-4<i>H</i>-dithieno­[3,2-<i>b</i>:2′,3′-<i>d</i>]­pyrrole as π-conjugating linkers, were synthesized and compared to the well-known LEG4 dye. The performance of the dyes was investigated in combination with an electrolyte based on Co­(II/III) complexes as redox shuttles. The electron recombination between the redox mediators in the electrolyte and the TiO₂ interface decreases upon the introduction of 4-hexylybenzene entities on the 2,5-di­(thiophen-2-yl)-1<i>H</i>-pyrrole and 4<i>H</i>-dithieno­[3,2-<i>b</i>:2′,3′-<i>d</i>]­pyrrole linker units, probably because of steric hindrance. The open circuit photovoltage of WS1-, WS2-, WS3-, and WS4-based devices in combination with the Co­(II/III)-based electrolyte are consistently higher than those based on a I^–/I₃^– electrolyte by 105, 147, 167, and 75 mV, respectively. The WS3-based devices show the highest power conversion efficiency of 7.4% at AM 1.5 G 100 mW/cm² illumination mainly attributable to the high open-circuit voltage (<i>V</i>_OC)

2,5-Dithienylpyrrole (DTP) as a donor component in DTP-π-A organic sensitizers: Photophysical and photovoltaic properties

Organic dyes have been prepared to evaluate the ability of 2,5-dithienylpyrrole (DTP) to act as a donor substituent in D-pi-A sensitizers for DSSCs. Using a styryl pi-bridge the dyes were found to be excellent sunlight harvesters when adsorbed on TiO2 photoanodes with absorbances >3 in the 300-550 nm region. Calculations as well as transient absorption spectroscopy in both solution and on a TiO2 surface revealed that they were favourable for efficient injection and regeneration.Organic dyes have been prepared to evaluate the ability of 2,5-dithienylpyrrole (DTP) to act as a donor substituent in D-π-A sensitizers for DSSCs. Using a styryl π-bridge the dyes were found to be excellent sunlight harvesters when adsorbed on TiO 2 photoanodes with absorbances >3 in the 300-550 nm region. Calculations as well as transient absorption spectroscopy in both solution and on a TiO 2 surface revealed that they were favourable for efficient injection and regeneration