Chalcogenide Glass Thin Films for Nanodipole Junctionless Photovoltaics
- PDF / 267,916 Bytes
- 6 Pages / 432 x 648 pts Page_size
- 92 Downloads / 150 Views
Chalcogenide Glass Thin Films for Nanodipole Junctionless Photovoltaics Sakina Junaghadwala1, Daniel G. Georgiev1, Victor G. Karpov2, Rossen Todorov3, Nanke Jiang1 1
Department of Electrical Engineering and Computer Science, University of Toledo, Toledo, OH 43606, U.S.A. 2 Department of Physics and Astronomy, University of Toledo, Toledo, OH 43606, U.S.A. 3 Institute of Optical Materials and Technologies “Acad. J. Malinowski”, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., bl.109, 1113 Sofia, Bulgaria ABSTRACT We examine the potential of Bi-Ge-Se chalcogenide glass films as materials for a new type of photovoltaic devices, referred to as junctionless nanodipole PV. Glasses of a chemical composition providing a significant optical absorption were synthesized in quartz ampoules from high-purity Bi, Ge, and Se elements by a conventional melt quenching technique. This material was then used to deposit thin films with different thicknesses on various substrates by thermal evaporation under high-vacuum conditions. The original bulk glasses and the films were characterized by electron microscopy with EDS, XRD, Raman spectroscopy, differential scanning calorimetry, and spectrophotometry. Open-circuit voltage (Voc) readings under incandescent illumination were obtained from the as-deposited and annealed films. Results from this characterization work are presented and discussed. Although the efficiency of nanodipole PV material structures, based on this material remains of no practical interest, our initial results indicate a possible path for the implementation of the nanodipole PV concept. INTRODUCTION Junctionless photovoltaic (PV) devices that employ the electric field of aligned nanodipoles, instead of junctions, for the separation of photogenerated carriers were proposed recently [1]. The active PV material consists of nano particles that possess uncompensated electric dipole moment and are embedded in a photoconductive host. Such PV material structures would offer potential benefits in terms of simplicity of fabrication, environmental friendliness, and cost. While various combinations of nanocrystals and host materials, and related fabrication methods could be explored, chalcogenide glass systems are among the most promising. These materials have been studied for decades, and a substantial amount of information has been accumulated. In particular, the chalcogenide glass systems offer optical bandgap energy close to the optimum values needed in PV applications. The composition of such glasses can be tuned and also modified with other elements in order to change their electrical properties in a desirable way. In this work, we present results from an initial study of the potential of chalcogenide glass films as materials for these new PV devices. The idea was to obtain films consisting of a dispersed nanocrystalline phase in a glassy host material that has suitable optical and electrical properties. This approach is based on observations that most nano-particles possess significant dipole moments related to their
Data Loading...
