Title
Challenges and opportunities of electron beam evaporation in the preparation of poly-Si thin film solar cells
Date Issued
20 December 2010
Access level
metadata only access
Resource Type
conference paper
Author(s)
Sontheimer T.
Becker C.
Ruske F.
Klimm C.
Bloeck U.
Gall S.
Kunz O.
Young T.
Egan R.
Hüpkes J.
Helmholtz-Zentrum Berlin für Materialien und Energie
Abstract
Electron-beam (e-beam) evaporation provides both exciting opportunities and challenges for the preparation of poly-crystalline silicon (poly-Si) thin film solar cells. A conversion efficiency of 6.7% was recently achieved for solid phase crystallized poly-Si mini-modules on planar SiN-coated glass deposited at a deposition rate of 600 nm/min, demonstrating the excellent electronic quality of e-beam evaporated silicon. Even at significantly increased background pressures of 5×10-6 mbar, the photovoltaic performance of the mini-modules was considerably high, showing a decline in open circuit voltage of 17 mV per cell. The implementation of light trapping structures into the device led to an efficiency increase of 1.1%, yielding module efficiencies of 7.8%. By systematically studying the implementation of ZnO:Al as a front contact layer into the poly-Si solar cell device structure, we unraveled novel features that prove the supreme suitability of ZnO:Al for poly-Si thin film solar cells. Not only can etched ZnO:Al be utilized as a front side texture, but its electrical properties can also improve during the crystallization process of the Si layer, showing a record charge carrier mobility of 67 cm2/Vs after thermal annealing. In addition, ZnO:Al drastically modifies the crystallization kinetics of the Si on ZnO:Al, enabling us to control the crystallization process by adjusting the deposition temperature. The nucleation process of Si on ZnO:Al was found to be influenced by a variation of the deposition temperature of the amorphous Si in a critical temperature regime of 200 °C to 300 °C. The nucleation rate decreased significantly with decreasing deposition temperature, while the activation energy for nucleation increased from 2.9 eV at a deposition temperature of 300 °C to 5.1 eV at 200 °C, resulting in poly-Si which comprised grains with features sizes of several μm. © 2010 IEEE.
Start page
614
End page
619
Language
English
OCDE Knowledge area
Ingeniería del Petróleo, (combustibles, aceites), Energía, Combustibles Recubrimiento, Películas
Scopus EID
2-s2.0-78650133433
ISSN of the container
01608371
ISBN of the container
9781424458912
Conference
Conference Record of the IEEE Photovoltaic Specialists Conference: 35th IEEE Photovoltaic Specialists Conference, PVSC 2010
Sources of information: Directorio de Producción Científica Scopus