Title :
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
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, Eopt 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 Eopt 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;
Conference_Titel :
Photovoltaic Specialists Conference, 1990., Conference Record of the Twenty First IEEE
Conference_Location :
Kissimmee, FL
DOI :
10.1109/PVSC.1990.111884
