Ziqing Lu

The electronic properties of ultra-narrow armchair MoS 2 nanoribbons

Single-layer ultra-narrow MoS₂ armchair nano-ribbons (AMoS₂NRs) are studied by density functional theory (DFT) in this paper. The width of AMoS₂NRs is classified by the number of dimer lines (N) across the ribbons. Ultra-narrow bare AMoS₂NRs with N=4, 5, 6 and 7 are indirect band gap semiconductors, different from cases where AMoS₂NRs with N>7 and N=3. The reason is ascribed to the different ratio of states provided by d-orbitals of Mo atoms to states by p-orbitals of S atoms for AMoS₂NRs with different widths. After passivation of edge atoms by hydrogen, most AMoS₂NRs become direct band gap semiconductors except for AMoS₂NR with N=4.

High performance of large-sized dye sensitized solar cells based on a novel low-cost metal grids manufactured process

In this study, a novel low-cost fabrication process of Al-based metal gr ids for large-sized dye sensitized solar cells (DSSCs) was developed. The Al-based metal grids layer is introduced by sputtering deposition on FTO glass to collect current and reduce the RTCO of large area DSSCs. With the Al-based metal gr ids technology, we achieved 4.8% conversion efficiency in the active area of 12.8cm2, an improvement by 120% in contrast with the counterpart without using the Al-based metal grids technology.

Application of Pre-corrected FFT in Statistical Power Analysis considering spatial correlations

In this paper, we introduce the Pre-corrected FFT (PFFT) algorithm in Statistical Power Analysis of CMOS ICs. We implemented PFFT to compute the Matrix Vector Product (MVP), resulted from the process of deducing the standard deviation of leakage current. To analyze power consumption statistically in a chip of N gates, the application of PFFT can reduce the computation complexity from O(N2)to O(Nlog2N). While maintaining an acceptable errors (less than 1%), the proposed method can dramatically accelerating the computation.

Thickness effect of nanocrystal TiO 2 photoanodes on Dye Sensitized Solar Cells (DSSC) performances

In this paper, the thickness effect of TiO₂ photoanodes on Dye Sensitized Solar Cells (DSSCs) is investigated. The optimization thickness of 12~15μm nanocrystal TiO₂ is experimentally demonstrated and reproduced by simulation for the large-size DSSCs (4cm-4cm). The simulation shows that thinner TiO₂ electrodes lead to smaller current due to the shortage of the absorbed dye molecular but thicker TiO₂ electrodes also cause the same effect due to the enhanced dark reaction between electrons in the TiO₂ and the electrolytes and the loss of the electrons during transportation in TiO₂ electrodes.

Properties of oxygen vacancy in W-doped monoclinic HfO2 based on the first principle calculations

In this paper, density functional theory (DFT) calculations of formation energy and relaxed structure were performed in W-doped HfO2 system, and electrical levels of oxygen vacancy and vacancy chain were also compared in monoclinic HfO2. The simulation shows that the formation energy of threefold and fourfold oxygen vacancy in the vicinity of W atom is lower compared to dopant-free monoclinic HfO2. However, the formation energy of oxygen vacancy far from dopant keeps the same. The dopant W atom makes the oxygen vacancy states shifted downward, and at the same time, the shallow level of 5d states may cause the electrons more easily to be thermally activated to be free conduction carriers.

Design and optimization of larger-sized dye sensitized solar cell (DSSC)

This paper addressed several critical issues that impact the performance of the larger-sized dye sensitized solar cells (DSSCs). We have demonstrated that the photoanode has the significant effect on the performances of DSSCs including the short current, open voltage, fill factor and conversion efficiency. Several novel structure designs on the photoanode are proposed to improve the performance of the larger-sized dye sensitized solar cells (DSSCs).