The mobility gaps in a-Si:H and its effects on solar cell performance

Author

Lee, S. ; Arch, J.K. ; Fonash, S.J. ; Wronski, C.R.

Author_Institution

Dept. of Electr. Eng., Pennsylvania State Univ., University Park, PA, USA

fYear

1990

fDate

21-25 May 1990

Firstpage

1624

Abstract

Internal photoemission of both electrons and holes was used to investigate the movement of mobility edges in a-Si:H. Shifts of the electron mobility edges were observed with changes in the optical gap, E_opt due to temperature and incorporation of hydrogen. Mobility gaps of 1.8 to 1.9 eV were measured for plasma-assisted CVD (chemical-vapor-deposited) films with optical gaps from 1.73 to 1.76 eV. The large effects of the differences between E _opt and the mobility gap in a-Si:H on solar cell performance are demonstrated using detailed numerical modeling of the maximum open-circuit voltage. The results obtained show that, for the commonly used a-Si:H materials with E_opt from 1.70 to 1.75 eV, the maximum open-circuit voltage that can be obtained, even with p-i-n homojunction cells, is 1.0 eV. This indicates that the V _oc in present solar cells is not limited by the intrinsic properties of the a-Si:H

Keywords

amorphous semiconductors; carrier mobility; elemental semiconductors; hydrogen; silicon; solar cells; amorphous Si:H solar cells; electron mobility edges; electron photoemission; hole photoemission; mobility gaps; open-circuit voltage; optical gaps; p-i-n homojunction cells; plasma-assisted CVD; Charge carrier processes; Electron mobility; Electron optics; Optical films; Optimized production technology; Photoelectricity; Photovoltaic cells; Plasma measurements; Plasma temperature; Voltage;

fLanguage

English

Publisher

ieee

Conference_Titel

Photovoltaic Specialists Conference, 1990., Conference Record of the Twenty First IEEE

Conference_Location

Kissimmee, FL

Type

conf

DOI

10.1109/PVSC.1990.111884

Filename

111884