High-efficiency polycrystalline CdTe thin-film solar cells

Cadmium telluride is a promising photovoltaic material for thin-film solar cells. However, further improvements on performance and reproducibility of devices have been limited by the conventional SnO₂/poly-CdS/poly-CdTe device structure used for more than 30 years. In this paper, we review partial R&D approaches at NREL to understand the issues related to the conventional device structure and to develop several novel materials and a modified device structure for minimizing these issues. We have achieved a CdTe polycrystalline thin-film solar cell demonstrating an NREL-confirmed, total-area efficiency of 16.5% by using new materials and the modified device structure. To apply the high-efficiency CdTe cell fabrication technique, we developed two manufacturing processes for producing high-efficiency CdTe modules with the potential of high throughput and low cost.     

Contactless probing of the intrinsic carrier transport single-walled carbon nanotubes

Intrinsic carrier transport properties of single-walled carbon nanotubes have been probed by two parallel methods on the same individual tubes： The contactless dielectric force microscopy （DFM） technique and the conventional field-effect transistor （FET） method. The dielectric responses of SWNTs are strongly correlated with electronic transport of the corresponding FETs. The DC bias voltage in DFM plays a role analogous to the gate voltage in FET. A microscopic model based on the general continuity equation and numerical simulation is built to reveal the link between intrinsic properties such as carrier concentration and mobility and the macroscopic observable, i.e. dielectric responses, in DFM experiments. Local transport barriers in nanotubes, which influence the device transport behaviors, are also detected with nanometer scale resolution.     

n沟增强型InP MISFET研究

在掺Fe的<100>晶向半绝缘 InP上,用 TEOS为源的 PECVD SiO_2作为栅氧化层,以Si~+注入 S.I.InP形成源、漏区,研制成基于 InP/SiO_2界面的n沟增强型 InP MISFET.其饱和区跨导 g_m为6.4mS/mm,沟道有效电子迁移率 μ_(eff)为1400cm~2/V·S,并对 InP MISFET特性及漏电流慢漂移行为作了讨论与分析.     

Electrical conductivity of textured Sm and Nd Co-doped CeO2 thin-film electrolyte

Nanocrystalline thin-film electrolytes of Sm³⁺ and Nd³⁺ co-doped ceria have been deposited on polycrystalline alumina substrates via RF magnetron sputtering. It is found that with the increase of substrate temperature from room temperature to 600 °C, the structure of the film varies from (1 1 1) preferred orientation to random orientation, accompanied by an enhancement in electrical conductivity. It is estimated that the activation energy for oxygen ion migration along (1 1 1) orientation may be higher than other crystal orientations, resulting in a lower conductivity of the (1 1 1) barrier textured co-doped ceria film electrolyte. It also indicates that the electrical conduction is predominantly due to the oxygen ions.     

Chiral sensing system based on the formation of diastereomeric metal complex on a homocysteine monolayer using field effect transistor

A self-assembled monolayer (SAM) of l-homocysteine (l-Hcy) formed on the surface of a gold-deposited gate of a field effect transistor (FET) was used to differentiate between enantiomers of amino acids, for which the formation of diastereomeric metal complexes is fundamental for chiral discrimination. Here, we focus our attention on the dependence of the FET response on the analyte amino acids, the central metal ions involved in complex formation, and the solution pH. Using the l-Hcy SAM-modified gate with added Cu(II), notable negative FET responses were enantioselectively observed for the l-enantiomers of alanine (Ala), phenylalanine, and tryptophan, whereas differences in the FET responses between enantiomers were negligible for asparagine and aspartic acid. Regarding the enantioselectivity for Ala, the addition of Cu(II) was demonstrated to show higher selectivity as compared to other metal ions such as Co(II) and Ni(II). Moreover, for the addition of l-Ala and Cu(II), a particularly strong negative FET response was observed at pH 5.5.     

The influence of preparation conditions on electrochemical properties of LiNi0.5Mn1.5O4 thin film electrodes by PLD

LiNi_0.5Mn_1.5O₄ thin films were prepared by pulsed laser deposition (PLD) on stainless steel substrates. The growth of the films has been studied as a function of substrate temperature and oxygen partial pressure in deposition, using X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM). Electrochemical properties of LiNi_0.5Mn_1.5O₄ thin film cathodes were investigated using cyclic voltammetry and galvanostatic charge/discharge against a lithium anode. The initial capacity and capacity retention of the films are highly dependent on the crystallinity and purity of the films. LiNi_0.5Mn_1.5O₄ thin films grown at 600 °C in an oxygen partial pressure of 200 mTorr are well crystallized with high purity, exhibiting excellent capacity retention between 3 and 5 V with a LiPF₆-based electrolyte.