Yueli Liu

Charge generation and transfer performance enhancement of size-balanced CuInS2 quantum dots sensitized solar cells

The optical absorption and charge dynamics of different sized CuInS2 quantum dots have been investigated. Exact sizes from 2.5 to 4.1xa0nm of CuInS2 quantum dots are prepared and further deposited on the TiO2 films. The optical absorption property of CuInS2 quantum dots sensitized photo-electrodes are analyzed by UV–Vis spectra, which provides electron generation property of the photo-electrodes. And the electron–hole separation property of the photo-electrodes is characterized by photoluminescence spectra with different size of quantum dots. The electrochemical impedance spectra and time-resolved photoluminescence decay are employed to measure the charge dynamics, which indicates that better electron transfer property can be obtained by the small size of quantum dots. With the balance of charge generation and charge transfer performance, 3.6xa0nm sized CuInS2 QDs sensitized photo-electrodes achieves excellent photovoltaic performance.

Sodium vanadate nanoflowers/rGO composite as a high-rate cathode material for sodium-ion batteries

Herein, Na5V12O32 has a low conductivity, which restricts its electrochemical performance. In order to use Na5V12O32 in practical sodium-ion batteries (SIBs), nanoflowers were prepared hydrothermally to enhance the electronic conductivity with the increasing of the effective surface area. Each nanoflower has 2D nanosheets with the thickness of ca. 10xa0nm and length up to 150xa0nm. Na5V12O32 nanoflowers were then embedded with reduced graphene oxide (rGO) by solid-state reaction process, which gives rise to fast electron transfer. The cathodic behaviour of 5–15xa0wt% rGO composites with Na5V12O32 nanoflowers is investigated. As a cathode material for SIBs, Na5V12O32 nanoflowers/rGO–10xa0wt% composite has a redox potential ca. 2.9xa0V versus Na+/Na and exhibits an excellent reversible cycling with initial discharge capacity of 142 mAhxa0g−1 at a rate of 5C. In addition, Na5V12O32 nanoflowers/rGO–10xa0wt% composite has a tap density of 3xa0gxa0cm−3 and volumetric energy density 1242xa0Whxa0L−1. These preliminary results indicate that the Na5V12O32 nanoflowers/rGO–10xa0wt% composite is a promising cathode candidate for SIBs.

Morphologies controllable synthesis of MoS 2 by hot-injection method: from quantum dots to nanosheets

Layered MoS2, which is treated as an alternative candidate of graphene, has attracted great attention due to its large intrinsic band gap and relatively high carrier mobility. It is relatively convenient and inexpensive to prepare MoS2 through chemical synthesis route. Herein, a novel solution-based hot-injection method is used to prepare MoS2. Controlling the reaction time leads to the variation of MoS2 morphologies, which present as quantum dots and nanosheets. Detail studies are carried out to investigate the formation mechanism of MoS2. The results indicate that the formation of layered MoS2 nanosheets follows a bottom-up process, which includes three steps in the order of quantum dots, small pieces and large area nanosheets.

Performance enhancement of quantum dot sensitized solar cells under TiO 2 nanotube arrays membranes optimization

One-dimensional single crystalline TiO2 nanotube arrays with different length are prepared, and transferred onto the FTO glass substrate with different concentration of Ti-precursor. The relationships between the concentration of Ti-precursor and the optical properties, as well as the photovoltaic performance of the as-prepared solar cells have been investigated. The optical absorption intensity is obviously enhanced and optical absorption edge is expanded to 800 nm for the CdSe/CdS/TiO2 NTs solar cells. In addition, 20 μm - CdSe/CdS/TiO2 NTs solar cells with 0.1 M Ti-precursor have the great photovoltaic conversion efficiency of 4.18%. The excellent photovoltaic performance is attributed to the suitable TiO2 connection layer from 0.1 M Ti-precursor and length of TiO2 NTs, which greatly enhances the electron-hole generation and charge transfer performance in the solar cells. Finally, the photovoltaic efficiency of the as-fabricated solar cells can be further enhanced to 4.51% through the ZnS passivation layer deposition.