Amorphous thin films for solar cell application. Quarterly report No. 3, October 1, 1979-December 31, 1979

The identification, content, and role of impurities in a-Si thin films are sources of speculation not only for possible device performance degradation but also for their impact on film-property diagnosis. This concern is presently shared by those using all deposition processes, with oxygen and argon receiving attention as the most commonly introduced impurities. Oxygen to some degree (and with nitrogen) might have beneficial effects on film photoconductivity; yet device performance is said to suffer when oxygen concentration approaches one percent. Argon inclusion effects on film structure, resulting post-deposition oxidation, and the nature of the defect state are indicated but unclear. Emphasis this quarter was on (1) the measurement of oxygen concentration profiles through the film using Rutherford backscattering and nuclear reaction methods; and (2) the control over oxygen inclusion in the sputtered films. Progress is reported in detail

Amorphous thin films for solar cell application. Final technical report, March 15, 1979-February 29, 1980

Magnetron sputtering, a deposition method in which magnetic confinement of a plasma encourages high deposition rates at low working gas partial pressures, is under investigation in this program as a candidate production technology for large-scale manufacture of high-efficiency, thin-film amorphous silicon solar photovoltaic cells. The approach uses two dc magnetron geometries: (1) a low-cost planar magnetron (PM) system for exploratory and detailed examination of deposition parameter space; and (2) a cylindrical magnetron (CM) system, scalable to production sizes, for deposition of homogeneous films over large areas. Detailed descriptions of these two systems are included. During this first-year effort, amorphous silicon films and device structures were sputtered in both PM and CM systems under a wide range of deposition conditions (i.e., T/sub s/, P/sub Ar/, P/sub H/sub 2//) using both doped and undoped sputter targets. Measured electrical and optical film properties indicate that control over a wide range of conductivity, photoconductivity, conductivity activation energy, and optical and infrared absorption behavior is achievable. Multiple depositions to fabricate simple MIS device structures and simultaneously to deposit monitor samples of individual constituent layers have been successful. Other program highlights are: (1) deposition rates as great as 1500 A/min were achieved in high-power dc magnetron operation at practical substrate-target spacings; (2) p-type and n-type a-Si:H consistently deposited from p- and n-type targets, respectively; (3) demonstrated correlation of argon and hydrogen partial pressure variations with optical, electronic, and structural properties of magnetron-sputtered a-Si:H films; and (4) initial depositions have achieved properties comparable to those in films made by rf sputtering and glow-discharge methods

Amorphous thin films for solar cell application. Quarterly report No. 2, July 1-September 30, 1979

Research on the fabrication of efficient amorphous silicon solar cells is reported. Work on the deposition of a-Si:H films by sputtering is described. Other areas under scrutiny include (a) degree and effect of oxygen and/or argon incorporation into the films, (b) dopant transfer from target to films, (c) dopant and alloy ion-implantation effects, and (d) film annealing behavior. Results to date are presented. (WHK

Amorphous thin films for solar cell application. Quarterly report No. 1, March 31-June 30, 1979

The prospects for generation of significant electric power using low-cost photovoltaic solar cells seem brighter with recent developments in sensitive impurity doping of glow-discharge-produced films of amorphous silicon containing large amounts of hydrogen (a-Si:H). The approach being taken to achieve the program objective centers on substituting sputtering for glow-discharge in the deposition of the a-Si:H films. Both planar and cylindrical forms of magnetron sputtering are being investigated in this program. Brief descriptions of the systems being used are presented. The planar system has the advantage that experimental costs are low; the cylindrical system is easily scalable to large product throughput. A-Si:H films are being prepared by magnetron sputtering, with reactive gases and/or doped Si targets, to achieve a reproducible and controllable process for the fabrication of solar cell devices. Ion implantation is being used for alloying and doping studies. This allows for a rapid and systematic survey of alloy materials, such as H, F and transition metals, for reducing mid-gap states, and also dopants, such as B, P and As, for conductivity control. In addition to being a flexible exploratory tool, ion implantation also has the potential for incorporation into large-scale production processes. The first quarter program plan emphasis was on film deposition, ion implantation and characterization. Progress is rported. (WHK

Cadmium sulfide/copper sulfide heterojunction cell research : final report for period February 26, 1979- May 31, 1980 /

"June 1980."Includes bibliographical references (pages 5/1-5/3).Work performed under contract no. ;Mode of access: Internet

Cadmium sulfide/copper sulfide heterojunction cell research : technical progress report for September 1 - November 30, 1979 /

"February 1980.""LMSC-D682102."Includes bibliographical references.Work performed under contract no. ;Mode of access: Internet