Projects

Polycrystalline Thin Films

University of South Florida

Publications

Project Objective:  The primary objective of this work is to develop a high band gap II-VI- based device that can serve as the top cell in an all-thin-film tandem structure that can achieve an efficiency of 25%. Inherent to this objective is the need to develop window layers that can serve as effective p-type contacts.  A secondary objective is to contribute to the knowledge base and understanding of this topic and provide additional contact options for single junction devices.

Approach/Background:  The Solar Cell Laboratories at USF have facilities for the complete fabrication and evaluation of thin-film solar cells.  Nevertheless, USF has provided cost sharing funds that will be used to build a new deposition system that will be specifically designed to fabricate devices for this project.  Consequently, during the initial stages of the project emphasis will be on constructing and bringing up the new deposition system.  However, during this period some materials development work will be undertaken using existing facilities.

Standard materials and evaluation procedures will be utilized throughout the course of work, including IV, CV, QE, XRD, SEM/EDS, and other specialized analytical techniques where needed.  An important new aspect of this project is the need to evaluate the optical properties of the device, especially in terms of transmitted light to the lower cell in a tandem structure.  USF has just set up a new spectrophotometer that includes an integrating sphere that will greatly enhance its capabilities in this area.

Status/Accomplishments:   During this brief period of the project the following has been accomplished:

• The design for the new deposition system supported by USF cost-sharing funds has been completed. The component parts have been ordered from various vendors, and space in the lab is being prepared.
• Modeling of device structures has been initiated using the AMPS-1D modeling code. Early models are based upon MIS structures that have exhibited the best performance to date.
• Device fabrication has been started with existing deposition equipment. Encouraging results have already been attained on transparent substrates. 

Planned FY 2002 Activities: 
Construct Deposition System
    (a) USF shall assemble the system and complete its installation.
    (b) USF shall bring the system up to its operational design
         specifications and begin utilization of the system for project work.

Fabricate Complete Device Structures
    (a) USF shall fabricate complete device structures of the best candidate films.
    (b) USF shall achieve 11% efficiency in diagnostic devices.

Characterize and Evaluate Device Performance
    (a) USF shall evaluate the sunlight performance of diagnostic devices.
    (b) USF shall evaluate the optical coupling of light to a bottom cell.
    (c) USF shall measure and characterize material properties.
    (d) USF shall measure and characterize device properties,
         including use of simulation programs such as AMPS.

University of South Florida High-Performance PV Publications:
"Development of a II-VI-Based High Performance, High Band Gap Device for Thin-Film Tandem Solar Cells," National Center for Photovoltaics Program Review Meeting, Oct. 14-17, 2001 (Lakewood, CO). (PDF 198 KB)

C. S. Ferekides and D. L. Morel