Chad Kamler

Formation of pyrite (FeS2) thin films by thermal sulfurization of dc magnetron sputtered iron

Iron films deposited by direct current magnetron sputtering onto glass substrates were converted into FeS2 films by thermal sulfurization. Experiments were carried out to optimize the sulfurization process, and the formation of FeS2 thin films was investigated under different annealing temperatures and times. High quality FeS2 films were fabricated using this process, and single phase pyrite films were obtained after sulfurization in a sulfur and nitrogen atmosphere at 450 °C for 1 h. Film crystallinity and phase identification were determined by using x-ray diffraction. The cubic phase pyrite films prepared were p-type, and scanning electron microscopy studies exhibited a homogeneous surface of pyrite. The authors have found that the best Ohmic contact for their pyrite thin films, using inexpensive metals, was Ni. The following were chosen for the study: Al, Mo, Fe, and Ni, and the one that led to the lowest resistance, 333 Ω, was Ni.

Self assembled nanoparticle aggregates from line focused femtosecond laser ablation

In this paper we present the use of a line focused femtosecond laser beam that is rastered across a 2024 T3 aluminum surface to produce nanoparticles that self assemble into 5-60 micron diameter domed and in some cases sphere-shaped aggregate structures. Each time the laser is rastered over initial aggregates their diameter increases as new layers of nanoparticles self assemble on the surface. The aggregates are thus composed of layers of particles forming discrete layered shells inside of them. When micron size aggregates are removed, using an ultrasonic bath, rings are revealed that have been permanently formed in the sample surface. These rings appear underneath, and extend beyond the physical boundary of the aggregates. The surface is blackened by the formation of these structures and exhibits high light absorption.

Chemical bath deposition (CBD) of iron sulfide thin films for photovoltaic applications, crystallographic and optical properties

A low temperature chemical deposition method has been developed to deposit iron/sulfur thin films onto soda lime glass substrates. The chemical bath deposition (CBD) consists of aqueous solution ferrous sulphate, disodium salt of ethylenediaminetetra-acetic acid (Na2EDTA), sodium thiosulphate and organic solutions of ethylenediamine and methanol. The experiments were performed at room temperature and under two different conditions. The films were uniform and adhered well to the soda lime glass substrates. The deposited films were additionally processed in a sulfur and nitrogen atmosphere at a variety of different temperatures to form the pyrite phase of FeS2. The as-deposited and annealed thin films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), optical absorption, auger electron spectroscopy (AES), and resistivity. The optimization of the FeS2 pyrite growth parameters was determined using XRD. Although both methods appeared to form FeS2 the second method is the preferable one where additional sulfurization at 450 °C for one hour yielded the films with the maximum crystalline order and stoichiometry.

Reaction pathway insights into the solvothermal preparation of CuIn 1−x Ga x Se 2 nanocrystalline materials

Reaction pathway investigations of the solvothermal preparation of nanocrystalline CuIn<inf>1−x</inf>Ga<inf>x</inf>Se<inf>2</inf> in triethylenetetramine reveal the early formation of a previously unreported Cu<inf>2−x</inf>Se(s) intermediate. Over 24 hours, this reacts with In and Se species to form CuInSe<inf>2</inf>(s). If Ga is present, the reaction proceeds over an additional 48 hours to form CuIn<inf>1−x</inf>Ga<inf>x</inf>Se<inf>2</inf>. Adding ammonium halide salts reduces the CuInSe<inf>2</inf> formation time to as little as 30 minutes. It is proposed that in these cases, Cu<inf>2−x</inf>Se particle growth is limited via a competitive Cu-halide complex formation. The smaller Cu<inf>2−x</inf>Se particles may react and form CuInSe<inf>2</inf> more rapidly. A reaction pathway scheme consistent with experimental results and previous literature reports is proposed.

Copper-Indium-Boron-Diselenide Absorber Materials

ABSTRACT Attempts to fabricate new CuIn 1-x B x Se 2 (CIBS) and CuBSe 2 (CBS) thin-film materials have been complicated by the formation of interfering crystallites and by the loss of boron from the magnetron sputtered precursor alloys during the selenization and annealing processes. Raman and Auger spectroscopic analysis as well as X-ray diffraction studies show that the formation of boron selenide may be contributing to the difficulty in creating these new materials. INTRODUCTION While much progress has been made in photovoltaic cell development, the United States still does not have a cost-competitive version of a solar cell for domestic or industrial applications except in very remote areas of the country. In order for photovoltaic systems to be competitive, a 15% module efficiency with an installed efficiency of 12% at a cost of

Problems with Synthesis of Chalcopyrite CuIn1-xBxSe2

1/Wp and a 20 year lifetime must be achieved. Broad-based U.S. government-supported research has determined that this goal can most likely be met by thin-film solar cells [1]. Of these thin film materials, the CuInSe

Ex-situ and in-situ selenization of copper-indium and copper-boron thin films

Thin films of CuIn1-xBxSe2 (CIBS) as absorption layer in single-junction solar cells can potentially grant a higher band gap in comparison with other studied chalcopyrite materials like CuIn1-xGaxSe2 (CIGS) and CuIn1-xAlxSe2 (CIAS). The higher band gap near optimum value ~ 1.4 eV can help to achieve higher efficiency (today 19.5% for CuIn0.74Ga0.26Se2). In this paper are described first results of experiments with effort to produce CIBS films by selenization of CuInB precursor alloy in Se vapors. Resulting material was analyzed by Raman spectroscopy, X-ray diffraction, and Auger electron spectroscopy. Measurements show that formation of CIBS layer is complicated by forming of pure CuInSe2 layer with unwanted Cu2-xSe phases and by accumulation boron near to the substrate.

A non-vacuum process for preparing nanocrystalline CuIn1−xGaxSe2 materials involving an open-air solvothermal reaction

It has recently been established that the ideal bandgap for terrestrial photovoltaics is 1.37 eV and the bandgap for CuInSe2 is only around 1.04 eV. Thus, a larger bandgap is needed. However, neither the substitution of Ga nor of Al has made a high efficiency solar cell absorber with a band gap of 1.37 eV possible. B, an even smaller atom, should require less atomic substitution than either Ga or Al to achieve a wider bandgap. In order to fabricate a thin film of CuInxB1-xSe2 (CIBS), Cu, In and B were deposited from a variety of sputtering targets which were pure Cu, In, and B; a Cu.45In.55; and a Cu3B2 target. Films were deposited simultaneously and sequentially. After deposition these films were post selenized in another vacuum chamber. Analysis of these films was accomplished using Raman spectroscopy, X-ray diffraction (XRD), and Auger electron spectroscopy (AES). With the difficulties encountered, materials were also deposited in a selenium atmosphere.