A postsynthesis assembly approach, an ex situ ligand exchange route, was developed for fast (within 2 h) and high loading (34% coverage) deposition of CdSe QDs on TiO(2) films. With the combination of high-quality QD sensitizers and the effective deposition technique, a record photovoltaic performance with an efficiency of 5.4% was observed for the resulting cell device.

We report here on the synthesis and photophysical/electrochemical properties of a series of novel starburst triarylamine-based organic dyes (S1, S2, S3, and S4) as well as their application in dye-sensitized nanocrystalline TiO2 solar cells (DSSCs). For the four designed dyes, the starburst triarylamine group and the cyanoacetic acid take the role of electron donor and electron acceptor, respectively. It was found that the introduction of starburst triarylamine group to form the D-D-pi-A configuration brought about superior performance over the simple D-pi-A configuration, in terms of bathochromically extended absorption spectra, enhanced molar extinction coefficients and better thermo-stability. Moreover, the HOMO and LUMO energy levels tuning can be conveniently accomplished by alternating the donor moiety, which was confirmed by electrochemical measurements and theoretical calculations. The DSSCs based on the dye S4 showed the best photovoltaic performance: a maximum monochromatic incident photon-to-current conversion efficiency (IPCE) of 85%, a short-circuit photocurrent density (J(sc)) of 13.8 mA cm(-2), an open-circuit photovoltage (V(oc)) of 0.63 V, and a fill factor (ff) of 0.69, corresponding to an overall conversion efficiency of 6.02% under 100 mW cm(-2) irradiation. This work suggests that the dyes based on starburst triphenylamine donor are promising candidates for improvement of the performance of the DSSCs.

Dye-sensitized solar cells (DSSCs) are promising for utilizing solar energy. To achieve high efficiencies, it is vital to synergistically improve the photocurrent (Jsc) and the photovoltage (Voc). In this respect, conjugation framework extension and cosensitization are effective for improving the absorption and the Jsc, which, however, is usually accompanied by undesirably decreased Voc. Herein, based on a rationally optimized porphyrin dye, we develop a targeted coadsorption/cosensitization approach for systematically improving the Voc from 645 to 727, 746, and 760 mV, with synergistical Jsc enhancement from 18.83 to 20.33 mA cm(-2). Thus, the efficiency has been dramatically enhanced to 11.5%, which keeps the record for nonruthenium DSSCs using the I2/I3(-) electrolyte. These results compose an alternative approach for developing highly efficient DSSCs with relatively high Voc using traditional iodine electrolyte.

Two novel metal-free dyes (DPP-I and DPP-II) with a diketopyrrolopyrrole (DPP) core were synthesized for dye-sensitized solar cells (DSSCs). The absorption spectra and electrochemical and photovoltaic properties of DPP-I and DPP-II were extensively investigated. Electrochemical measurement data indicate that the tuning of the HOMO and LUMO energy levels can be conveniently accomplished by alternating the π-conjugated systems. Besides, coadsorption of chenodeoxycholic acid (CDCA) can hinder the formation of dye aggregates and might improve electron injection yield and, thus, J sc. This has also led to a rise in the photovoltage, which is attributed to the decrease of charge recombination. The DSSC based on dye DPP-I showed better photovoltaic performance: a maximum monochromatic incident photon-to-current conversion efficiency (IPCE) of 80%, a short-circuit photocurrent density (J sc) of 9.78 mA cm−2, an open-circuit photovoltage (V oc) of 605 mV, and a fill factor (FF) of 0.69, corresponding to an overall conversion efficiency of 4.14% under standard global AM 1.5 solar light condition. This work suggests that the metal-free dyes based on a DPP core are promising candidates for improvement of the performance of DSSCs.