Meidan Que

Highly Efficient Flexible Perovskite Solar Cells Using Solution-Derived NiOx Hole Contacts

A solution-derived NiOx film was employed as the hole contact of a flexible organic-inorganic hybrid perovskite solar cell. The NiOx film, which was spin coated from presynthesized NiOx nanoparticles solution, can extract holes and block electrons efficiently, without any other post-treatments. An optimal power conversion efficiency (PCE) of 16.47% was demonstrated in the NiOx-based perovskite solar cell on an ITO-glass substrate, which is much higher than that of the perovskite solar cells using high temperature-derived NiOx film contacts. The low-temperature deposition process made the NiOx films suitable for flexible devices. NiOx-based flexible perovskite solar cells were fabricated on ITO-PEN substrates, and a preliminary PCE of 13.43% was achieved.

High efficiency hysteresis-less inverted planar heterojunction perovskite solar cells with a solution-derived NiOx hole contact layer

A hysteresis-less inverted planar heterojunction perovskite solar cell with 14.42% power conversion efficiency (PCE) was successfully fabricated by employing a solution-derived NiOx film as the hole selective contact. Here, the non-stoichiometric transparent NiOx film is composed of a lot of small NiOx nanocrystals with a cubic crystal structure. Inverted planar heterojunction perovskite solar cells based on the as-prepared NiOx hole selective contacts show a much higher PCE and air storage stability than the control device fabricated from the PEDOT:PSS film as the hole selective contact, since NiOx has a better electron blocking property due to its high conduction band edge position. The thickness of the NiOx contact strongly influences the performance of the NiOx-based perovskite solar cells, which include the PCE, hysteresis behaviors and air storage stability due to the thickness-dependent morphology of the NiOx contact.

Warm white light generation from a single phased phosphor Sr10[(PO4)5.5(BO4)0.5](BO2):Eu2+, Mn2+, Tb3+ for light emitting diodes

A novel single phased white light emitting phosphor Sr10[(PO4)5.5(BO4)0.5](BO2):Eu2+, Mn2+, Tb3+ was synthesized by solid-state reaction for the first time. The crystal structure, photoluminescence properties and the efficient energy transfer from different Eu2+ sites to Mn2+ and Tb3+ in Sr10[(PO4)5.5(BO4)0.5](BO2) is studied in detail by X-ray diffractometry Rietveld method, luminescence spectra, energy-transfer efficiency and lifetimes. Through effective energy transfer, the wavelength-tunable warm white light can be realized with superior chromaticity coordinates of (0.37, 0.30) and low correlated color temperature (CCT = 3512 K) by coupling the emission bands peaking at 410, 542 and 649 nm attributed to the contribution from Eu2+, Tb3+ and Mn2+, respectively. The results indicate the white phosphor Sr10[(PO4)5.5(BO4)0.5](BO2):Eu2+, Mn2+, Tb3+ can serve as a promising material for phosphor-converted warm white LEDs.

TiO2 passivation for improved efficiency and stability of ZnO nanorods based perovskite solar cells

Zinc oxide (ZnO) has been demonstrated to be a superb electron selective contact material in photovoltaic devices for its high electron mobility and various accessible nanostructures. However, issues of severe charge recombination and thermal instability occurring at the perovskites/ZnO interface hinder its application on perovskite solar cells. Herein, we report a strategy of TiO2 passivation onto the surface of ZnO nanorods (NRs) using a wet-chemical method, where a device structure FTO/ZnO NRs/TiO2 passivation layer/CH3NH3PbI3/spiro-OMeTAD/Ag is adopted. Based on the proposed strategy, an overall power conversion efficiency (PCE) of 13.49% is achieved mainly due to the improved open-circuit voltage (Voc) of 1.02 V, shirt-circuit current density (Jsc) of 20.69 mA cm−2, and fill factor (FF) of 0.64, which are much higher than those of bare ZnO NRs-based devices. Interestingly, TiO2 passivated samples show much better long-term device stability than those without passivation, where TiO2 acts as a buffer layer with improved thermal stability owning to reduced chemisorbed hydroxyl groups as indicated by X-ray photoelectron spectroscopy.

Low temperature solution processed indium oxide thin films with reliable photoelectrochemical stability for efficient and stable planar perovskite solar cells

Organometallic halide-based perovskite solar cells (PSCs) have attracted significant research attention among the next-generation photovoltaic technologies, in which the electron transport layer (ETL) plays a crucial role in the PSC performances of power conversion efficiency and long-term stability. Herein, we proposed a low temperature solution-processing route to prepare indium oxide thin films on ITO substrates with an acetylacetone-chelated precursor, which exhibit better film morphology, well-aligned band structure, and enhanced electron extraction capacity. As a result, the PSC fabricated from the as-prepared indium oxide film as the ETL shows a promoted maximum efficiency of 15.30% and steady-state efficiency of 14.39%, which are a record for indium oxide-based PSCs. More significantly, the indium oxide film shows minimum photocatalytic activity compared with ZnO and TiO2 films, which leads to excellent light and shelf-life device stability. After storage in the dark for three months, the power conversion efficiency of the unsealed PSCs based on the indium oxide films degrades slightly, which retain approximately 94% of their peak efficiency.

Enhanced photoluminescence property of sulfate ions modified YAG:Ce3+ phosphor by co-precipitation method

Abstract The sulfate ions modified YAG:Ce 3+ phosphors were prepared by co-precipitation method and characterized by X-ray diffraction, transmission electron microscopy, and photoluminescence. Effects of sulfate ions on the photoluminescence (PL) property of the as-prepared YAG:Ce 3+ phosphors were studied, with sodium dodecyl sulfate (SDS) being added to R 3+ (Ce 3+ , Y 3+ , Al 3+ ) ions. Results indicated that pure YAG:Ce 3+ phosphors with different ratios of sulfate ions could be easily obtained by calcining the as-synthesized precursor at 950 °C for 2 h, the YAG:Ce 3+ phosphors with an optimal mass ratio of 3.5 wt.% SDS had the highest emission intensity and the best dispersion behavior, and the fluorescence decay of the as-obtained YAG:Ce 3+ phosphors was related to the lattice defect, reabsorption and cross correlation. Furthermore, thermal quenching properties of the YAG:Ce 3+ phosphors and the YAG:Ce 3+ phosphors with 3.5 wt.%SDS were also discussed, indicating that the YAG:Ce 3+ with SDS phosphors could have potential applications in the daylight LEDs or warm white LEDs.

Enhanced Conversion Efficiencies in Dye-Sensitized Solar Cells Achieved through Self-Assembled Platinum(II) Metallacages.

Two-component self-assembly supramolecular coordination complexes with particular photo-physical property, wherein unique donors are combined with a single metal acceptor, can be utilized for many applications including in photo-devices. In this communication, we described the synthesis and characterization of two-component self-assembly supramolecular coordination complexes (SCCs) bearing triazine and porphyrin faces with promising light-harvesting properties. These complexes were obtained from the self-assembly of a 90° Pt(II) acceptor with 2,4,6-tris(4-pyridyl)-1,3,5-triazine (TPyT) or 5,10,15,20-Tetra(4-pyridyl)-21H,23H-porphine (TPyP). The greatly improved conversion efficiencies of the dye-sensitized TiO2 solar cells were 6.79 and 6.08 respectively, while these SCCs were introduced into the TiO2 nanoparticle film photoanodes. In addition, the open circuit voltage (Voc) of dye-sensitized solar cells was also increased to 0.769 and 0.768 V, which could be ascribed to the inhibited interfacial charge recombination due to the addition of SCCs.

Highly efficient and reproducible planar perovskite solar cells with mitigated hysteresis enabled by sequential surface modification of electrodes

Fullerene-based derivatives passivation and TiCl4 treatment are widely used as interfacial modification methods in planar perovskite solar cells for enhancing efficiency, stability and reducing hysteresis. Although the two kinds of surface modifications have been separately reported to modify the metal oxide or even directly modify the electrodes, the resulting device performance is still moderate. Herein, we report a sequential surface modification of FTO by combining a low-temperature processed ultrathin TiOx layer with a PCBM passivation layer, synergistically affording high efficiency and mitigated hysteresis and exhibiting good reproducibility for n–i–p planar perovskite solar cells. Based on this sequential modification strategy, the modified FTO substrates can effectively facilitate electron transfer and suppress interfacial recombination. As a result, we obtain efficient perovskite solar cells with the best power conversion efficiency (PCE) of 18.26% and the stabilized PCE of 17.22%. Additionally, we demonstrate that this facile sequential surface modification method gives rise to highly reproducible device performance with the average PCE of 17.16%. Beyond that, the photocurrent hysteresis is effectively suppressed for the obtained solar cells compared with the single modified analogues owing to facilitated electron transfer at the interface.

Photoluminescence and energy transfer of YAG: Ce3+, Gd3+, Bi3+

In this study, Gd3+ and Bi3+ ions act to redshift the emission band to orange region, and to enhance significantly the maximum emission of YAG: Ce3+. On account that size mismatch between the host and the doped Gd3+ ion, the crystal structure turns soft, and the emission spectra are not tuned from 540 to 570nm but decreased the emission intensity. Accordingly, an effective way to increase emission intensity is to introduce Bi3+ ion into the YAG: Ce3+, Gd3+ phosphors. Experimental results show partial overlapping between the emission band of Bi3+ ion and the excitation band of Ce3+ ion, indicating that the energy transfer from Bi3+ to Ce3+ ions exists in the (Y1.94Ce0.06Gd)Al5O12: Bi3+ phosphor. Bi3+ ion can serve as the activator to provide energy for Ce3+ ion via cross relaxation phenomenon. Therefore, the (Y1.94Ce0.06Gd)Al5O12: Bi3+ phosphor could have potential applications in warm white LEDs.