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Three novel dithieno[3,2-f:2′,3′-h]quinoxaline-based organic dyes (IQ-C, IQ-D and IQ-F) with three π-spacers were synthesized and developed for dye sensitized solar cells, where dithieno[3,2-f:2′,3′-h]quinoxaline was used as electron-withdrawing π-spacers, and 2,3-diphenylquinoxaline or dibenzo[a,c]phenazine as auxiliary electron-withdrawing π-spacers. The dye IQ-D with 2,3-diphenylquinoxaline as auxiliary electron-withdrawing π-spacer exhibited higher photocurrent (Jsc) and photovoltage (Voc) than that of the dye IQ-C with 2,3-bis(4-(octyloxy)phenyl)quinoxaline as the additional electron-withdrawing π-spacer, due to the larger adsorption amount of IQ-D. The dye IQ-F with a rigid conjugated dibenzo[a,c]phenazine as additional electron-withdrawing π-spacer showed the highest efficiency of 6.54% under AM 1.5 G irradiation. It was demonstrated that the π-spacers influence the photovoltaic performance of the dithieno[3,2-f:2′,3′-h]quinoxaline-based organic dyes significantly. The results indicated that the dyes with three π-spacers are promising candidates for efficient dye-sensitized solar cells. [ABSTRACT FROM AUTHOR]

Three novel metal-free organic dyes IT , IPT and IQT , containing a dipentyldithieno[3,2- f :2′,3′- h ]quinoxaline ( DPQ ) unit as the π-bridge were synthesized and the impacts of the auxiliary acceptors on the photovoltaic performances were studied. IQT with 2,3-dipentylquinoxaline as the auxiliary acceptor exhibited the highest efficiency of 7.98%, with a short-circuit photocurrent density of 16.87 mA cm −2 , an open-circuit photovoltage of 0.71 V, and a fill factor of 0.67, under standard global AM 1.5G solar light condition. IPT with the strongest electron-withdrawing group (2,3-dipentylpyridopyrazine) as the auxiliary acceptor could red-shift the absorption range, but showed the weakest performance, which might be due to the electron trap of the 2,3-dipentylpyridopyrazine unit. The results show that incorporating auxiliary acceptor with moderate electron-deficient ability can extend the absorption range and adjust the molecular orbital energy levels, improving the photovoltaic performance. [ABSTRACT FROM AUTHOR]

Four novel D–π–A–π–A metal-free organic dyes Q1-Q4 were synthesized and the impacts of the auxiliary acceptors on the photovoltaic performances were studied. Q2 with quinoxaline as the auxiliary acceptor exhibited the best photovoltaic performance due to its highest short-circuit photocurrent density (17.22 mA cm −2 ), leading to a power conversion efficiency of 7.42% under simulated AM 1.5 G illumination. Q1 with the strongest electron withdrawing group (pyrazino[2,3- g ]quinoxaline) as the auxiliary acceptor showed the weakest performance, which can be attributed to electron trap and mismatch of energy-level. The results showed that the different electron-withdrawing property of auxiliary units significantly influenced the absorption, energy levels and photovoltaic performance. Incorporating auxiliary acceptor with moderate electron-deficient ability can extend the absorption range and adjust the molecular orbital energy levels, resulting in better photovoltaic performance. [ABSTRACT FROM AUTHOR]

Four novel organic dyes DT1-DT4 containing a dithienopyrrolobenzotriazole unit were synthesized and applied in dye sensitized solar cells, where dithienopyrrolobenzotriazole moiety was introduced as a π-spacer for the first time. The four dyes exhibited good light harvesting efficiency with high molar extinction coefficients and broad spectral response. The influence of the different electron donor on the photovoltaic performance was evaluated. The effects of the linear and branched alkyl chains in the π-bridge on the photophysical, electrochemical and photovoltaic performance were systemically investigated. The results show that branched alkyl chains are better than linear alkyl chains in inhibition of intermolecular aggregation and electron recombination between the injection electrons and electrolyte. Finally, DT4 sensitized solar cell obtained a power conversion efficiency of 8.05%. These results indicate that the dithienopyrrolobenzotriazole-based organic sensitizer is a promising candidate for efficient dye sensitized solar cells. [ABSTRACT FROM AUTHOR]

Two novel organic dyes TLEP-1 and TLEP-2 based on phenothiazine with trilateral π-conjugation extensions were designed and synthesized for dye-sensitized solar cells, where phenothiazine ring was linked with two phenyl moieties at 7- and 10-positions as the first and second π-conjugation extensions, and with furan or thiophene ring at 3-position as the third π-conjugation extension for TLEP-1 and TLEP-2 , respectively. The influence of the π-conjugation extensions on the photovoltaic performance was evaluated. The cell based on TLEP-2 exhibits an impressive short-circuit photocurrent density of 14.87 mA cm −2 , which is much higher than the cell based on the reference dye without π-conjugation extension (9.01 mA cm −2 ), leading to high power conversion efficiency of 7.33% under simulated AM 1.5 G illumination condition. The results indicate that the trilateral π-conjugation extensions are an effective way to improve the photovoltaic performance of the dye-sensitized solar cells. [ABSTRACT FROM AUTHOR]

A new di-anchoring organic dye based on phenothiazine featuring A-D-π-D-A (acceptor-donor-π-linker-donor-acceptor) configuration with fluorene as the π linker was designed and successfully synthesized. Compared to the corresponding mono-anchoring D-A congener, this new dye exhibited a broader and stronger absorption in the light wavelength ranging from 400 nm to 600 nm and thus showed a more efficient photovoltaic performance for dye-sensitized solar cells (DSSCs). The overall power conversion efficiency ( η ) of this new dye in a sensitized solar cell amounted to 5.70%, which is 17% higher than that of the equivalent based counterpart (4.87%). On the other hand, the introduction of two thiophene units at position-2 and -7 of the fluorene unit gave another new dye with extended conjugation. This extended conjugation dye showed a higher molar extinction coefficient ( ε ), but exhibited π-stacked aggregation on the TiO 2 surface, resulting in low efficiency of electron injection. The results indicate that the di-anchoring dye with fluorene as π linker is a promising candidate for efficient DSSCs. [ABSTRACT FROM AUTHOR]

Abstract: Three organic dyes with double D–A system were synthesized and applied in the dye-sensitized solar cells. These dyes contain phenothiazine as an electron donor and cyanoacetic acid as an acceptor/anchor. Linkages were incorporated at the ortho-, meta- and para-positions and their impact on the performance of photovoltaic was observed. Among them, the dye with a para-position linkage exhibited the highest short-circuit photocurrent density (12.26 mA cm−2) and open-circuit photovoltage (756 mV), leading to the best overall efficiency (6.14%) due to better light harvesting capacity under standard global 1.5 AM conditions. Under similar measuring conditions the dyes with ortho and meta-position linkage delivered sunlight to electricity conversion efficiencies of 5.25% and 5.85% respectively. The result shows the position isomer of the linkage units influences the photophysical characteristics, dye loading on the film and electron lifetime. [Copyright &y& Elsevier]

• Five new dithienopyrrolobenzothiadiazole-based organic dyes are reported. • DTPBT is used as donor for organic sensitizer for the first time. • W3 with phenothiazine shows better ability of suppressing electron recombination. • W5 sensitized DSSC achieves an efficiency of 7.98%. Five new dithienopyrrolobenzothiadiazole (DTPBT)-based organic sensitizers were prepared for dye-sensitized solar cells (DSSCs). In this work, DTPBT unit was used as a donor to construct mono- and di-anchored metal-free organic sensitizers for the first time. The DTPBT unit applied as a donor or a π-spacer in mono-anchored dyes (W1 and W2) greatly influences the absorption range, HOMO-LUMO energy level and the solar cell performance of the dyes. The results show that the DTPBT unit is more suitable for acting as a π-spacer in D-π-A dyes. Di-anchored dyes exhibit broader photo-spectra response and higher molar extinction coefficients than those of the mono-anchored dyes. Di-anchored dyes W4 and W5 with DTPBT as the donor, thiophene as the π-bridge achieve high power conversion efficiencies of 7.93%, 7.98% with 1 mM CDCA as the co-adsorbent, respectively. The results suggest that the DTPBT moiety is a promising donor candidate to develop efficient double anchored organic dyes for DSSCs. [ABSTRACT FROM AUTHOR]

Abstract: Three novel metal-free organic dyes with dihydro-5H-dibenzo[b,f]azepine as a donor and cyanoacrylic acid as an anchoring unit were designed as an innovative linear skeleton of D–D–π–A type of organic dyes. The conversion efficiency of the derived dye-sensitized solar cells is moderate. Among them, the dye with a hydroxy group as an additional anchoring moiety exhibited the highest UV–Vis absorption with a maximum molar extinction coefficient of 24,136 M−1 cm−1 at λ max = 458 nm and the best photovoltaic performance with an overall power conversion efficiency of 4.88%, while the dye with a carboxy group as an additional anchoring moiety exhibited the lowest conversion efficiency (4.52%). The results show that the dye loading on the film and photovoltaic performance of the dyes were influenced by the additional anchoring units. [Copyright &y& Elsevier]