Shujie Jiao

A stable and efficient quasi-solid-state dye-sensitized solar cell with a low molecular weight organic gelator

High power conversion efficiency and long-term stability are significant targets for practical applications of dye-sensitized solar cells. Here, we present a quasi-solid-state dye-sensitized solar cell that incorporates a low molecular weight organic gelator-based electrolyte in conjunction with a high-absorptivity ruthenium sensitizer C105, exhibiting an impressive power conversion efficiency of 9.1%. By means of transient absorption and electrical impedance measurements, we scrutinize the impacts of the additive low molecular weight organic gelator in a low-volatility 3-methoxypropionitrile electrolyte on the photovoltaic characteristics of dye-sensitized solar cells with a sensitizer C105. The quasi-solid-state dye-sensitized solar cell also retains excellent thermal and light-soaking stability during 1000-h accelerated aging tests.

Ultralong Rutile TiO2 Nanowire Arrays for Highly Efficient Dye-Sensitized Solar Cells.

Vertically aligned rutile TiO2 nanowire arrays (NWAs) with lengths of ∼44 μm have been successfully synthesized on transparent, conductive fluorine-doped tin oxide (FTO) glass by a facile one-step solvothermal method. The length and wire-to-wire distance of NWAs can be controlled by adjusting the ethanol content in the reaction solution. By employing optimized rutile TiO2 NWAs for dye-sensitized solar cells (DSCs), a remarkable power conversion efficiency (PCE) of 8.9% is achieved. Moreover, in combination with a light-scattering layer, the performance of a rutile TiO2 NWAs based DSC can be further enhanced, reaching an impressive PCE of 9.6%, which is the highest efficiency for rutile TiO2 NWA based DSCs so far.

Gas sensing properties of self-assembled ZnO nanotube bundles

Large-scale ZnO nanotube bundles were synthesized by a simple solution-based method under mild conditions. The structural and optical properties of the resultant products were characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption–desorption and photoluminescence techniques. The sensor based on the ZnO nanotube bundles exhibited excellent sensing properties against ethanol gas at the operating temperature of 230 °C. The sensitivity of the sensor to 100 ppm ethanol was approximate 25.2 with a rapid response time (about 3 s). It was found that the ZnO nanotube bundle sensor displayed significantly better sensing performances due to a larger surface area and more electron donor related oxygen vacancies in comparison with the ZnO nanorod bundle sensor.

Realization of unbiased photoresponse in amorphous InGaZnO ultraviolet detector via a hole-trapping process

A metal-semiconductor-metal (MSM) structure ultraviolet photodetector has been fabricated from amorphous InGaZnO (a-IGZO) film at room temperature. The photodetector can work without consuming external power and show a responsivity of 4 mA/W. The unbiased photoresponse characteristic is attributed to the hole-trapping process occurred in the electrode/a-IGZO interface, and a physical model based on band energy theory is proposed to explain the origin of the photoresponse at zero bias in our device. Our findings may provide a way to realize unbiased photoresponse in the simple MSM structure.

Efficient photocatalyst based on ZnO nanorod arrays/p-type boron-doped-diamond heterojunction

The ZnO nanorod arrays (NRs) have been fabricated on p-type boron-doped diamond (BDD) substrate by hydrothermal method. It was demonstrated that the density and diameter of the ZnO NRs can be effectively controlled by adjusting the reactant concentration. Photocatalytic activity of the fabricated ZnO NRs/p-BDD heterojunction was investigated for the degradation of methyl orange dye and the results indicated that diameter and density of ZnO NRs play a very important role in photocatalytic degradation. Furthermore, the ZnO NRs/p-BDD heterostructure photocatalysts are easily recycled and reused.

Realization of a fast-response flexible ultraviolet photodetector employing a metal–semiconductor–metal structure InGaZnO photodiode

Amorphous InGaZnO (a-IGZO) thin films have been grown on polyethylene terephthalate (PET) substrates using a plasma-assisted pulsed laser deposition (PLD) technique, and a flexible ultraviolet (UV) photodetector (PD) with a simple metal–semiconductor–metal (MSM) structure was prepared on the a-IGZO films. The flexible PD shows relatively good photoresponse characteristics before and after bending, and retains good folding reproducibility after repeated bending up to 500 cycles. More importantly, it shows a fast speed with response and recovery times of 0.8 ms and 2.0 ms, 33.8 ms, which are much faster than that of the reported flexible ultraviolet detectors. The devices reported in this paper provide an optimal way to realize flexible ultraviolet detectors with fast speed.

Tunable growth of PbS quantum dot–ZnO heterostructure and mechanism analysis

The potential applications of quantum dots on wide band gap semiconductor structures in flexible and large-scale optoelectronics demand fundamental analysis of their tunable growth. Herein, PbS quantum dots (<5 nm) on a ZnO heterostructure are formed by a successive ionic layer adsorption and reaction method. Well distributed PbS quantum dots on ZnO are achieved just by changing the solvent of Pb(NO3)2 and analyzed from the view of solvent-related interaction and adhesion between a hydrophobic substrate and self-assembled layers. This solvent-related distribution of PbS quantum dots on ZnO is confirmed by scanning electron microscopy and transmission electron microscopy, which shows that a fine distribution of PbS quantum dots on ZnO is feasible by using more ethanol in the solvent of Pb(NO3)2. With the aim towards tunable growth of a PbS on ZnO heterostructure, the effects of concentration and dipping times on the size and structure of PbS quantum dots are also explored, which demonstrates that the size of quantum dots is mainly controlled in the thermodynamic domain. Meanwhile, the stoichiometric ratio of Pb and S can also be tuned by changing the dipping times. Most significantly, their optical and electrical properties also show an obvious solvent-related characteristic, which provides another key factor for the potential fabrication and application of quantum dot based devices.

An interfacial defect-controlled ZnO/PbS QDs/ZnS heterostructure based broadband photodetector

An in situ successive ionic layer adsorption and deposition method is introduced for fabrication of PbS QDs-on-ZnO heterostructures, which improves carriers transport within PbS QDs by eliminating the introduction of ligands. By suitably controlling the interface related defects characteristics through solvent adjustment, broadband photodetection ranging from 340 nm to 840 nm is achieved. Most significantly, improved device performance is achieved even in the case that no obvious type-II heterostructure is formed between ZnO and PbS, which reminds us of the significant role of QD, defects control besides their size, shape and ligands adjustments.

Enhanced carrier localization in near-ultraviolet multiple quantum wells using quaternary AlInGaN as the well layers

The structural and optical properties of near-ultraviolet (UV) multiple quantum well (MQW) structures using quaternary AlInGaN as the well layers have been investigated. The composition of the barrier layers is determined by three In0.08Ga0.92N/AlxInyGa1−x−yN multiple quantum well samples with varying Al content in the barrier layers. The compositions of the well and barrier layers are estimated from the high-resolution X-ray diffraction (HRXRD) results. In spite of the larger lattice mismatch, the remarkable enhancement of the photoluminescence (PL) intensity of the MQWs sample with AlInGaN as the well layers is attributed to the increase in the carrier localized states induced by the increase in the compositional fluctuation in the AlInGaN well layers. The S-shaped temperature-dependence of the PL peak energy indicates the existence of localized states induced by the potential fluctuations. The magnitude of the carrier localization, which is estimated by the fitting results, is significantly increased in the Al0.11In0.13Ga0.76N/Al0.16In0.045Ga0.795N MQWs due to the improvement of the spatial potential fluctuations using quaternary AlInGaN as the well layers.

A novel TiO2 nanostructure as photoanode for highly efficient CdSe quantum dot-sensitized solar cells

For sensitized solar cells, photoanodes combining the advantages of TiO2 nanoparticles (high specific surface area) and one-dimensional (1D) nanostructures (fast transport channels) are ideal for obtaining highly efficient sensitized solar cells. In this paper, 1D connected TiO2 nanoparticles (1D CTNPs) were synthesized by a simple one-pot solvothermal reaction and utilized to fabricate CdSe quantum dot-sensitized solar cells (QDSSCs). To evaluate the effects of the 1D CTNPs on the performance of CdSe QDSSCs, another CdSe QDSSC was fabricated based on conventional TiO2 nanoparticles (TNPs), which were synthesized via a similar solvothermal route with a different reaction time. The 1D CTNP-based CdSe QDSSC showed an impressive light-to-electricity conversion efficiency of 5.45% accompanying an open-circuit voltage of 596 mV, a fill factor of 0.52, and a short-circuit current density of 17.48 mA cm−2. This efficiency is much higher than that of the TNP-based cell (4.00%). The significant enhancements in the open-circuit voltage, short-circuit current, and power conversion efficiency of the 1D CTNP-based CdSe QDSSC compared to the TNP-based cell are explained as follows. The 1D CTNP photoanode has large pores and a relatively high specific surface area, facilitating the loading of CdSe QDs and, most importantly, providing an efficient electron transport pathway, which effectively facilitates electron transport and prolongs electron lifetime. The excellent properties of the 1D CTNPs make them an optimal candidate as a photoanode material for highly efficient QDSSCs.