In this letter, the authors report a dye-sensitized solar cell (DSSC) using a ZnO-nanoflower film photoanode, which was grown by a hydrothermal method at 95°C. The dye used was cis-bis(isothiocyanato)bis(2,2′-bipyridyl-4,4′-dicarboxylato)-ruthenium(II) bis-tetrabutylam-monium (N-719). At AM1.5G irradiation with 100mW∕cm2 light intensity, the DSSC based on ZnO-nanoflower film showed an energy conversion efficiency of 1.9%, which is much higher compared to that (1.0%) of the control device constructed using a photoanode of upstanding ZnO-nanorod array fabricated by hydrothermal method as well. The better performance of ZnO-nanoflower DSSC was due to a better dye loading and light harvesting of the ZnO-nanoflower film. The results demonstrate potential application of ZnO-nanoflower array for efficient dye-sensitized solar cells.

We reported an efficient inverted bulk-heterojunction ͓regioregular of poly͑3-hexylthiophene͒: ͑6,6͒-phenyl C 61 butyric acid methyl ester͔ solar cell with a highly transparent sol-gel derived ZnO film as electron selective layer and MoO 3 as hole selective layer. By modifying the precursor concentration of sol from 0.75 to 0.1M, the optical transmittance of ZnO film increases from 75% to 95%. This improvement in transmittance increases the short-circuit density of inverted solar cell from 5.986 to 8.858 mA/ cm 2 without sacrificing the open-circuit voltage and fill factor of the device. We also demonstrated that the device incorporated with MoO 3 has a larger open-circuit voltage and fill factor than the device without MoO 3. Power conversion efficiency of 3.09% was achieved under simulated AM 1.5G illumination of 100 mW/ cm 2 .

Inkjet printing has been considered an available way to achieve large size full-color RGB quantum dots LED display, and the key point is to obtain printed film with uniform and flat surface profile. In this work, mixed solvent of 20 vol % 1,2-dichlorobenzene (oDCB) with cyclohexylbenzene (CHB) was used to dissolve green quantum dots (QDs) with CdSe@ZnS/ZnS core/shell structure. Then, by inkjet printing, a flat dotlike QDs film without the coffee ring was successfully obtained on polyetherimide (PEI)-modified ZnO layer, and the printed dots array exhibited great stability and repeatability. Here, adding oDCB into CHB solutions was used to reduce surface tension, and employing ZnO nanoparticle layer with PEI-modified was used to increase the surface free energy. As a result, a small contact angle is formed, which leads to the enhancement of evaporation rate, and then the coffee ring effect was suppressed. The printed dots with flat surface profile were eventually realized. Moreover, inverted green QD-LEDs with PEI-modified ZnO film as electron transport layer (ETL) and printed green QDs film as emission layer were successfully fabricated. The QD-LEDs exhibited the maximum luminance of 12 000 cd/m and the peak current efficiency of 4.5 cd/A at luminance of 1500 cd/m.

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Recently, organic light-emitting diodes (OLEDs) based on phosphorescent dyes have attracted increasing attention due to their potential application in full-color flat panel displays. Owing to the strong spin±orbital mixing of heavy-metal ions in phosphorescent complexes, both singlet and triplet excitons can be fully utilized, [1±5] creating the possibility for electrophosphorescent dye doped devices to reach an internal quantum efficiency of 100 %. Baldo et al.[5] first demonstrated extremely high-efficiency green phosphorescence OLEDs with fac-tris(2-phenylpyridine)iridium, [Ir(ppy) 3 ]. Devices with Ir(ppy) 3 doped into 4,4¢-N,N¢-dicarbazole-biphenyl (CBP) and 3-phenyl-4-(1¢-naphthyl)-5-phenyl-1,2,4-triazole (TAZ), show a high external quantum efficiency of 15 % ph/ el (photon/electron) and a power efficiency of 40 lm/W.[5±7]By modifying the ligand structure of phosphorescent dyes, emission can be tuned over the entire visible region.[8±13]The use of a conjugated polymer as the host material is attractive, since it allows light-emitting diodes (LEDs) to be made with a spin-coating or printing technique. Despite extensive work in many research groups, [14±16] the external quantum efficiency of polymer light-emitting diodes (PLEDs) based on phosphorescent dye doped into a polymer host is still much lower than that of small-molecule-based OLEDs. To date, the highest efficiency (external quantum efficiency (QE ext ) = 10 % ph/el, luminance efficiency (LE) = 32 cd/A, k max = 550 nm) for green phosphorescent PLEDs has been reported by Gong et al., [17] with tris[9,9-dihexyl-2-(pyridinyl- ]iridium(acetylacetonate) (BtpIr) into PVK, Chen et al. [18] attained an external quantum efficiency of 3.3 % ph/el and luminance efficiency (LE) of 2.6 cd/A with a peak emission at 614 nm. For the same system, a similarÐbut slightly lowerÐefficiency was also reported by Kawamura et al. [19] Gong et al. reported a high efficiency of QE ext = 5 % ph/el and LE = 7.2 cd/A with an emission maximum at 600 nm by doping tris(2,5-bis-2¢-(9¢,9¢-dihexylfluorene) pyridine) iridium(III) [Ir(HFP) 3 ] into PVK:PBD (40 %). [20] However, the same authors found that by replacing the PVK(PBD) host with a statistic conjugated co-polymer, poly(9,9-dihexylfluorene-co-2,5-dicyanophenylene) (PF3CNP1), the external quantum and luminous efficiencies of the [Ir(HFP) 3 ]/PF3CNP1 device were significantly reduced, to QE ext = 1.5 % ph/el and LE = 3 cd/A at 142 cd/m 2 .2¢[21] O'Brien and co-workers [22,23] achieved QE ext = 3.5 % ph/el with LE < 1 cd/A by doping PtOEP into poly(9,9-dioctylfluorene) (PFO), with an emission maximum at 646 nm. It seems that conjugated polymer (like PFO and CNPPP) [21±24] hosted phosphorescent PLEDs generally yield lower quantum efficiencies than the non-conjugated polymer, PVK. Sudhakar et al. attributed this phenomenon to phosphorescence quenching by conjugated polymers with a low-energy triplet state. [25] From a Stern±Volmer analysis of the quenching of phosphorescent emission by fluorene oligomers, they concluded that phosp...

Porphyrin-based dyes recently have become good candidates for dye-sensitized solar cells (DSCs). However, the bottleneck is how to further improve their light-harvesting ability. In this work, N-annulated perylene (NP) was used to functionalize the Zn-porphyrin, and four "push-pull"-type NP-substituted and fused porphyrin dyes with intense absorption in the visible and even in the near-infrared (NIR) region were synthesized. Co(II/III)-based DSC device characterizations revealed that dyes WW-5 and WW-6, in which an ethynylene spacer is incorporated between the NP and porphyrin core, showed pantochromatic photon-to-current conversion efficiency action spectra in the visible and NIR region, with a further red-shift of about 90 and 60 nm, respectively, compared to the benchmark molecule YD2-o-C8. As a result, the short-circuit current density was largely increased, and the devices displayed power conversion efficiencies as high as 10.3% and 10.5%, respectively, which is comparable to that of the YD2-o-C8 cell (η = 10.5%) under the same conditions. On the other hand, the dye WW-3 in which the NP unit is directly attached to the porphyrin core showed a moderate power conversion efficiency (η = 5.6%) due to the inefficient π-conjugation, and the NP-fused dye WW-4 exhibited even poorer performance due to its low-lying LUMO energy level and nondisjointed HOMO/LUMO profile. Our detailed physical measurements (optical and electrochemical), density functional theory calculations, and photovoltaic characterizations disclosed that the energy level alignment, the molecular orbital profile, and dye aggregation all played very important roles on the interface electron transfer and charge recombination kinetics.

A variety of novel light-emitting copolymers derived from 9,9-dioctylfluorene (DOF) and 2,1,3-naphthozoselenadiazole (NSeD) were prepared by the palladium-catalyzed Suzuki coupling reaction. The feed ratios of DOF to NSeD were 99.9:0.1, 99.5:0.5, 99:1, 98:2, 95:5, and 85:15. All of the polymers are soluble in common organic solvents and highly fluorescent in solid state. Devices based on the copolymers emit saturated red light, and the emission slightly red-shifted gradually with increasing NSeD's contents. The maximal external quantum efficiency of the polymer light-emitting devices (PLED) reaches 3.1%, and luminous efficiency is greater than 1.0 cd/A with emission maximum at 657 nm and Commission Internationale de L'Eclairage (CIE) coordinates of (0.64, 0.33). This is the highest efficiency with saturated red emission for a single-layer device with nonblend type emitter reported so far in the scientific literature. This indicates that the new EL polymers based on fluorene and naphthoselenadiazole are promising as a red emitter in polymer light-emitting displays.

We report efficient tandem organic solar cells with an Al and MoO3 intermediate layer. Such an intermediate layer with optimized thickness (1 nm Al and 15 nm MoO3) has high transparency (∼98% in the range from 350 to 900 nm) and efficient charge collections to realize electric connection in series. For polymer-small molecule tandem cell, due to the summation (1.01 V) of the open-circuit voltages of individual cells and a short-circuit current density of 6.05 mA/cm2, a power conversion efficiency (PCE) of 2.82% was obtained under 100 mW/cm2 illumination, which is larger than either of the individual cells. The PCE reached 3.88% when the tandem cell was illuminated under 300 mW/cm2. Additionally, we applied Al/MoO3 intermediate layer to realize a solution-processed polymer tandem cell with a high PCE (2.23%). The thick MoO3 (15 nm) provides a complete protection of the prior-deposited polymer layer from dissolving during the top cell polymer coating.