A novel organic small molecule bis-triphenylamine with spiro(fluorene-9,9′-xanthene) as the conjugated system, named BTPA-4, is successfully synthesized and employed as the hole-selective layer (HSL) in colloidal quantum dots solar cells (CQDSCs). The introduction of BTPA-4 layer can significantly prolong effective carrier lifetime (τeff), increase charge recombination resistance (Rrec), and thus diminish the interfacial charge recombination at the PbS-QDs/Au electrode interface. The effect of BTPA-4 as HSL in the device performance is especially significant for the open-circuit voltage (Voc) and power conversion efficiency (PCE), with a ∼ 10% and 15% enhancement respectively, comparing with those of device without the HSL. Furthermore, the PbS CQDSCs with BTPA-4 possessed a noticeably stable property for over 100 days of storage under ambient atmosphere.

•Novel Ru dyes with NˆNˆN or C−ˆNˆN pattern as an auxiliary ligand were designed.•Introduction of 2-hexylthiophene unit lowers the molar extinction coefficients.•The dyes with C−ˆNˆN pattern exhibited the IPCE up to a near-IR region (∼950 nm).•The efficiency of DSSC is higher with NˆNˆN complex than with C−ˆNˆN complex.Four new bistridentate Ru(II) complexes having a combination of ligands, 4,4′-dicarboxy-2,2′:6,2″-terpyridine or its 2-hexylthiophene-substituted derivative as the anchoring ligand on one hand and one of tetrazolylpyridine-based ligands having a NˆNˆN coordination pattern or C−ˆNˆN coordination pattern as the auxiliary ligand on the other are reported as sensitizers for dye-sensitized solar cells (DSSCs), along with their spectroscopic, electrochemical, and theoretical characterizations. For the anchoring ligand, the introduction of 2-hexylthiophene unit leads to narrower spectral response and lower molar extinction coefficients and a smaller driving force for dye regeneration. For the ancillary ligand, the cyclometalating RuC bond induces a red shift in absorption compared with a RuN bond and thus affords a photocurrent generation at wavelengths of up to 950 nm. Further, the overall efficiencies of DSSCs are higher with the NˆNˆN complexes than with the C−ˆNˆN complexes, mainly due to higher open-circuit voltages (Voc). Overall, the DSSC based on the bistetrazolate dye without the hexylthiophene unit for the anchoring ligand and having the NˆNˆN coordination pattern for the auxiliary ligand exhibited the highest efficiency of 5.9% when employing 0.5 M t-butylpyridine in the electrolyte.Download high-res image (159KB)Download full-size image

Upon mixing acetylacetonedioxime and copper(II) nitrate in water, the acetylacetonedioxime is spontaneously nitrosated at the central α-carbon and four of the nitrosated ligand molecules and five Cu ions self-assemble into a pentanuclear metallacrown complex, whose structure has been revealed by single crystal X-ray analysis and magnetic interactions between the Cu ions in the complex have been probed. The lability of the core Cu ion in the complex is suggested.

The first dendrimers consisting of self-assembled zinc chlorophyll derivatives are reported. Coordination-directed self-assembly of pyridine-appended zinc chlorophyll derivatives tethering a dendron moiety results in cyclic tetramers peripherally functionalized by dendrons via intermolecular axial coordination interaction between the nitrogen atom in the pyridine ring and the zinc atom in the chlorin ring. We characterized the formation of the cyclic tetramers by use of 1H NMR measurements including diffusion-ordered spectroscopy (DOSY). Four different types of dendrons were introduced in the zinc chlorophyll component to investigate the tolerance of the self-assembly to the dendron structure. All dendrimers exhibited similar stabilities, which demonstrates that the dendron moiety does not interfere with the self-assembly, such that more than 90% of the molecules are in the assembly at concentrations >0.2 mM in benzene.

The development of robust dyes is a highly important theme for any applications of dyes. Here we present photophysical and electrochemical characterization of a set of robust dyes based on the thienylnaphthalimide unit. The set is comprised of the thienylnaphthalimide derivatives with phenyl- (Ph-), 4-nitrophenyl- (NO2Ph-), and 4-(diphenylamino)phenyl (Ph2NPh-) substituents as exemplars covering electron-withdrawing to electron-donating groups. The fluorescence quantum yields of the Ph-TNI increases as the solvent polarity increases, while that of Ph2NPh-TNI showed the opposite trend. Changes in the rates of nonradiative decay were found to be a major factor for these contrasting behaviors. Cyclic voltammetry showed that the substituent effects were more apparent for the HOMO energies rather than the LUMO energies. Density functional theory calculations showed that the first singlet excited state of these compounds is a 1π,π* state with a significant charge transfer character. Ph-TNI and Ph2NPh-TNI are much more stable against photodegradation than coumarin and fluorescein dyes.

Self-assembled structures formed from a pyridine-appended zinc chlorophyll derivative are reported. While the zinc complex forms cyclic oligomers in chloroform solution, as indicated by 1H NMR studies (including diffusion-ordered spectroscopy), vapor pressure osmometry, and cold-spray ionization mass spectrometry, it forms double-stranded helical coordination polymers in the solid state, as revealed by single-crystal X-ray analysis.

•A panchromatic cyclometalated Ru complex is applied for dye-sensitized solar cells.•Absorption tail of this complex extends up to 800 nm.•Deprotonation induces large negative shifts in the redox potentials.•The short-circuit current of cell with our complex is better than that with N719.A cyclometalated ruthenium complex with 6-(ortho-methoxyphenyl)-2,2'-bipyridine (MeO-L) and tricarboxyterpyridine (tpy(CO2H)3) (RuCC·PF6) was prepared, characterized, and evaluated as a dye for dye-sensitized solar cells (DSSCs). The first oxidation and reduction potentials are +0.99 V and −0.81 V vs NHE, respectively. This complex exhibits panchromatic absorption spectrum extending up to 800 nm. The transitions upon visible light excitation were mixtures of metal-to-ligand (Ru → tpy(CO2H)3) and interligand (MeO-L → tpy(CO2H)3) charge transfer transitions. Adsorption of the ruthenium complex on TiO2 was carried out from solutions of RuCC·PF6 in the free acid form or solutions of RuCC·(NBu4)2 in a deprotonated carboxylate form. The DSSC devices employing these complexes as the dye sensitizers generate electricity in response to light over the whole visible range and into the near infrared region over 900 nm. Remarkably, RuCC·(NBu4)2 recorded higher short-circuit current density than a benchmark N719, while the open-circuit voltage was lower, resulting in a modest overall photon-to-current conversion efficiency of 6.4%. The transient absorption and electrochemical impedance spectroscopy have been conducted to get insight into the mechanistic details of the DSSC cells, which suggested that the presence of NBu4 cation was beneficial in retarding the unwanted recombination reaction. Considering the efficient charge injection and regeneration as manifested by the large short-circuit current, modification based on the present structure would be a promising strategy toward higher efficiency dyes for DSSCs.A new cyclometalated ruthenium dye has been prepared, characterized, and applied to dye-sensitized solar cells (DSSCs). The short-circuit photocurrent density of DSSCs using this complex as the sensitizer dye exceeded that of the benchmark dye N719 under the same conditions because of the near IR sensitivity.

Upon mixing acetylacetonedioxime and copper(II) nitrate in water, the acetylacetonedioxime is spontaneously nitrosated at the central α-carbon and four of the nitrosated ligand molecules and five Cu ions self-assemble into a pentanuclear metallacrown complex, whose structure has been revealed by single crystal X-ray analysis and magnetic interactions between the Cu ions in the complex have been probed. The lability of the core Cu ion in the complex is suggested.