Photovoltaic modeling and grain boundary recombination in poly-silicon

In the first part of this dissertation, an analytical approach to n⁺/p solar cells is developed. Based on this model, the short circuit current, open circuit voltage and energy conversion efficiency of the cells as a function of doping concentration, junction depth, minority carrier surface recombination velocity and diffusion length are discussed. This model simplifies the analysis of the solar cell, and the calculated results agree closely with both experimental results and numerical analysis. The second part of the dissertation deals with grain boundary (GB) recombination, passivation, and characterization. A simple GB model is developed, and an expression for the GB barrier height under illumination is derived by introducing a quasi Fermi-function. By using this model, the dependencies of the minority carrier transport parameters on the illumination level, grain size, depth from the surface and trap state density are derived. The model is compared to the experimental results for GB capacitance and electron lifetime measurements. Hydrogen passivation of poly-Si solar cells was accomplished experimentally by hydrogen implantation. A systematic study of implantation parameters was conducted and an optimum condition was found for the samples under examination. Under this condition, 18 % improvement in cell efficiency was achieved for the cells, with initial efficiencies of about 7%. A transmission electron microscope (TEM) study of the hydrogen-dislocation interaction and hydrogen ion bombardment effects on the surface were also conducted. The GB recombination velocity and the hydrogen passivation effect were characterized by the electron beam induced current (EBIC) technique. A nonuniform passivation depth was observed. The nature of the passivation mechanism was addressed. It was found that hydrogen saturation of dangling bonds in Si grain boundaries is not the only mechanism for hydrogen passivation.

Name thesis:degree_name

Ph. D.

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Materials Engineering Science

Department dc:contributor.department

Materials Engineering Science

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

1990

Author dc:creator

• Chen, Zhizhang

Chair dc:contributor.committeechair

• Burton, Larry C.

Committee members dc:contributor.committeemember

• Stephenson, F. William
• Elshabini-Riad, Aicha A.
• Chen, Dan Y.
• Desu, Seshu B.

• grain boundary

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en

Dc Identifier Other

etd-09162005-115034

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/39377