Determination of Cu Concentrations in CdTe/CdS Devices by High Mass Resolution Secondary Ion Mass Spectrometry

We have used secondary ion mass spectrometry (SIMS) to quantitatively determine the concentration of Cu in CdTe/CdS devices. Empirical standards were fabricated by ion implantation of Cu into single-crystal and polycrystalline CdTe and single-crystal CdS

Structural and electronic properties of Pb1-xCdxTe and Pb1-xMnxTe ternary alloys

A systematic theoretical study of two PbTe-based ternary alloys, Pb1-xCdxTe and Pb1-xMnxTe, is reported. First, using ab initio methods we study the stability of the crystal structure of CdTe - PbTe solid solutions, to predict the composition for which rock-salt structure of PbTe changes into zinc-blende structure of CdTe. The dependence of the lattice parameter on Cd (Mn) content x in the mixed crystals is studied by the same methods. The obtained decrease of the lattice constant with x agrees with what is observed in both alloys. The band structures of PbTe-based ternary compounds are calculated within a tight-binding approach. To describe correctly the constituent materials new tight-binding parameterizations for PbTe and MnTe bulk crystals as well as a tight-binding description of rock-salt CdTe are proposed. For both studied ternary alloys, the calculated band gap in the L point increases with x, in qualitative agreement with photoluminescence measurements in the infrared. The results show also that in p-type Pb1-xCdxTe and Pb1-xMnxTe mixed crystals an enhancement of thermoelectrical power can be expected.Comment: 10 pages, 13 figures, submitted to Physical Review

Cross-Section AFM and EFM Examination of Thin-Film Solar Cells

We demonstrated the feasibility of analyzing cross sections of thin-film CdTe/CdS and CIGS/CdS solar cells using atomic force microscopy (AFM)

Degradation and Capacitance-Voltage Hysteresis in CdTe Devices: Preprint

CdS/CdTe cells on CTO/ZTO TCO show greater intial performance than SnO2-gased substrates due to superior optical and electrical properties of the oxide layers and more rigorous CdCl2 processing. Performance unfiormity was a problem

Recrystallization of PVD CdTe Thin Films Induced by CdCl2 Treatment -- A Comparison Between Vapor and Solution Processes: Preprint

This paper describes the large concentration of 60..deg.. twin boundaries that was observed in every CdTe film analyzed in this work, even after recrystallization and grain growth, confirming the low energy of these interfaces

Cross-Sectional Conductive Atomic Force Microscopy of CdTe/CdS Solar Cells: Effects of Etching and Back-Contact Processes; Preprint

We investigated the effects of the etching processes using bromine and nitric-phosphoric acid solutions, as well as of Cu, in the bulk electrical conductivity of CdTe/CdS solar cells using conductive atomic force microscopy (C-AFM). Although the etching process can create a conductive layer on the surface of the CdTe, the layer is very shallow. In contrast, the addition of a thin layer of Cu to the surface creates a conductive layer inside the CdTe that is not uniform in depth, is concentrated at grains boundaries, and may short circuit the device if the CdTe is too thin. The etching process facilitates the Cu diffusion and results in thicker conductive layers. The existence of this inhomogeneous conductive layer directly affects the current transport and is probably the reason for needing thick CdTe in these devices

Advances in CdTe R&D at NREL

This paper summarizes the following R&D accomplishments at National Renewable Energy Laboratory (NREL): (1) Developed several novel materials and world-record high-efficiency CdTe solar cell, (2) Developed "one heat-up step" manufacturing processes, and (3) Demonstrated 13.9% transparent CdTe cell and 15.3% CdTe/CIS polycrystalline tandem solar cell. Cadmium telluride has been well recognized as a promising photovoltaic material for thin-film solar cells because of its near-optimum bandgap of ~1.5 eV and its high absorption coefficient. Impressive results have been achieved in the past few years for polycrystalline CdTe thin-film solar cells at NREL. In this paper, we summarize some recent R&D activities at NREL

SAMHD1 promotes DNA end resection to facilitate DNA repair by homologous recombination

DNA double-strand break (DSB) repair by homologous recombination (HR) is initiated by CtIP/MRN-mediated DNA end resection to maintain genome integrity. SAMHD1 is a dNTP triphosphohydrolase, which restricts HIV- 1 infection, and mutations are associated with Aicardi-Goutières syndrome and cancer. We show that SAMHD1 has a dNTPase-independent function in promoting DNA end resection to facilitate DSB repair by HR. SAMHD1 deficiency or Vpx-mediated degradation causes hypersensitivity to DSB-inducing agents, and SAMHD1 is recruited to DSBs. SAMHD1 complexes with CtIP via a conserved C-terminal domain and recruits CtIP to DSBs to facilitate end resection and HR. Significantly, a cancer-associated mutant with impaired CtIP interaction, but not dNTPase-inactive SAMHD1, fails to rescue the end resection impairment of SAMHD1 depletion. Our findings define a dNTPase-independent function for SAMHD1 in HR-mediated DSB repair by facilitating CtIP accrual to promote DNA end resection, providing insight into how SAMHD1 promotes genome integrity

Development strategy and lessons learned for a 10-valent pneumococcal conjugate vaccine (PNEUMOSIL®)

Pneumococcal conjugate vaccines (PCVs) have proven to be the best way to prevent severe childhood pneumococcal disease but until recently have been difficult for many countries to afford sustainably. In 2008, the Serum Institute of India, Pvt. Ltd. and PATH entered into a collaboration, funded in part by the Bill & Melinda Gates Foundation, to respond to this problem by developing a PCV designed to be affordable, accessible, and protective against the pneumococcal serotypes causing the most morbidity and mortality in low- and middle-income countries. The resulting 10-valent PCV (PNEUMOSIL®) received World Health Organization prequalification in December 2019 – making it just the third PCV to be certified as an option for Gavi, the Vaccine Alliance-eligible countries – and is being made available at a Gavi price of US$2/dose. The task of developing a state-of-the-art, yet lower-priced, PCV required public-private collaboration across geographies and yielded a variety of successes and learnings useful to the vaccine development field. Key among the learnings were factors related to manufacturing strategy and optimization, serotype selection, flexibility, early risk detection and mitigation, partner trust and continuity across similar-class products, complementary business philosophies, and early clarity of purpose