AVS 61st International Symposium & Exhibition
    Vacuum Technology Monday Sessions
       Session VT-MoA

Invited Paper VT-MoA10
VTD Early Career Award: Novel Vacuum Processing of Thin-Film Photovoltaic Materials

Monday, November 10, 2014, 5:00 pm, Room 303

Session: Vacuum Measurement, Applications of UHV and Ultraclean Processes
Presenter: Jason D. Myers, U.S. Naval Research Laboratory
Authors: J.D. Myers, U.S. Naval Research Laboratory
J.A. Frantz, U.S. Naval Research Laboratory
R.Y. Bekele, U.S. Naval Research Laboratory
V.Q. Nguyen, U.S. Naval Research Laboratory
C.C. Baker, U.S. Naval Research Laboratory
S.C. Erwin, U.S. Naval Research Laboratory
N.D. Bassim, U.S. Naval Research Laboratory
A. Bruce, Sunlight Photonics
S.V. Frolov, Sunlight Photonics
J.S. Sanghera, U.S. Naval Research Laboratory
Correspondent: Click to Email
In this presentation, two different avenues of research into thin film photovoltaics will be discussed. The first part of the talk will be focused on quaternary-sputtered Cu(In,Ga)Se2 (CIGS) thin film photovoltaic devices. Current state-of-the-art CIGS devices are produced using a multistage thermal coevaporation process that has resulted in laboratory efficiencies in excess of 20%, but this process is difficult to implement at a commercial scale. Our work has instead focused on developing a scalable deposition technique using RF magnetron sputtering of quaternary CIGS. The resulting films do not require post-selenization, reducing processing time and cost. We have fabricated devices above 10% efficiency using this approach, showing its promise as a production method for high-performance CIGS.

The second part of the talk will be focused on an emerging thin film photovoltaic system, FeS2. Based on its favorable bandgap, high absorption coefficient, and immense earth abundancy, FeS2 is a highly promising material for grid-scale energy production. However, no successful thin-film photovoltaic devices have been realized due to surface defect states that arise due to the cubic pyrite structure, where sulfur atoms are differentially bonded at the surface compared to the bulk; this leads to extremely low open circuit voltages and poor diode characteristics. To solve this issue, we are developing vacuum-deposited inorganic capping films to heal these defects by providing bulk-like coordination at the FeS2 surface. FeS2 films with ZnS capping layers show a significant decrease in surface state character, an important step towards efficient FeS2 photovoltaics.