Fabrication and characterization of porous silicon photovoltaic devices

Dissertant

Jafar, Ayyub Hasan

Thesis advisor

Nayif, Adi Muhsin

University

University of Technology

Faculty

-

Department

Applied Sciences Department

University Country

Iraq

Degree

Master

Degree Date

2012

English Abstract

Porous silicon (PS) layers have been prepared in this work by electrochemical etching (ECE) technique of a (111) p-type silicon wafer with resistivity (1.5-4 Ω.cm) in hydrofluoric (HF) acid of 20% concentration.

Various affecting parameters were studied such as the current density (10, 20, 40, and 50 mA/cm2), and etching time (10, 20, and 40 min).

We have studied the optical properties (Reflectivity), vibration properties (Raman), surface properties (FTIR), structural properties (XRD), morphological properties (AFM), and electrical properties (I-V, C-V, photocurrent, and photosensitivity).

Also we prepared PS layers by ECE for p-n silicon at different current densities (5, 10, and 40 mA/cm2) with fixed etching time at 20 min, in 20% HF acid, in order to study the photovoltaic measurements for solar cell.

The PS surface showed lower reflectance values compared with bulk silicon.

Raman spectra measurements showed a broadened peak and shifted below 520 cm-1 for PS layers.

In freshly prepared PS layer, the FTIR studies demonstrated the presence of siliconhydrogen bonds, related to groups formed at the extended PS surface.

As the PS layers were stored, various silicon-oxygen vibrational modes became apparent.

X-ray diffraction showed when crystal size was reduced toward nanometric scale, then a broadening of diffraction peaks (111) were observed and the width of the peak was directly correlated to the size of the nanocrystalline domains.

AFM images showed the PS layer had sponge like structure, and average diameter of pore and thickness of PS layer increased with increasing the current density and etching time.

The electrical properties of prepared PS; namely current density voltage characteristics in dark, showed that the pass current through the PS layer decreased by increasing the current density and etching time, due to increase the resistivity of PS layer.

The PS layer showed a rectifying behaviour with different rectification ratio.

CV measurements demonstrated that the charge carries decrease and width of depletion layer increase by increasing the current density and etching time.

The photosensitivity measurements of prepared PS layer showed the peak value in visible region at (400- 600nm) increased with increasing the current density and etching time.

Main Subjects

Physics

Topics

• Optical properties

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-418913