Fabrication of (GeS2)‎100-x Gax n,p-Si& p-Ge heterojunction solar cell

Other Title(s)

تصنيع (GeS2)‎100-x Gax n,p-Si& p-Ge مفرق هجين خلية شمسية

Dissertant

Kazim, Muhammad Abd al-Hurr

Thesis advisor

Hasan, Bushra Abbas
al-Haddad, Rad Muhammad Salih

Comitee Members

Yahya, Khalid Z.
Abd al-Majid, Inam Muhammad
Suhayl, Mahdi Hasan
Shaban, Salma Mahdi
Ali, Salih M.
Hasan, Nahidah Bakhit

University

University of Baghdad

Faculty

College of Science

Department

Department of Physics

University Country

Iraq

Degree

Ph.D.

Degree Date

2013

English Abstract

Bulk (GeS2)100-xGax samples were prepared with different Ga contents (0, 6, 12 and 18%) by quenching technique.

Thin films prepared by using thermal evaporation under vacuum of 10-5 mbar on glass, n-Si , p-Si and p-Ge single crystals substrates at different substrate temperature (303, 373 and 473)K with deposition rate (10-15nm/min) at 300 nm thickness.

The structures of (GeS2)100-xGax bulk and films have been studied by X–ray diffraction technique.

The results showed that all alloys have polycrystalline structures and the peaks at Ga content =0 and 6% were identical with the GeS2 standard peaks, except at 12 and 18% another peaks appeared corresponding to Ga2S3 and Ga phases, while all thin films have amorphous structures.

AFM measurements showed the increasing in both average grain size and average surface roughness with the increasing of substrate temperature, while showed a non systematic behavior with the increase Gallium content.

The optical measurements show that the (GeS2)100-xGax films have indirect energy gap Eg opt decreases with the increase of substrate temperatures and Ga content for all samples, But the optical constants such as refractive index (n), extinction coefficient (k) and dielectric constant (εr, εi) have a regular increase with the increase of substrate temperatures and Ga content.

The D.C measurements appears that there is one activation energy for GeS2 transport to two activation energy Ea1 and Ea2 as the gallium introduces into GeS2 system.

The values of activation energies are VI decrease with the increase of both the Ga contents and substrate temperatures.

While the conductivity increased with increasing of substrate temperatures and with Ga contents.

Hall Effect measurements showed that all the (GeS2)100-xGax thin films are p-type semiconductors for different Ga contents at Ts=303K, but the increase of substrate temperature led to appeared an alternative change to n-type with increasing the Ga content.

Concentration of charge carriers nH having a maximum value for samples prepared at (303) K with Ga content12% and increasing with Ga content at (373 and 473) K.

The mobility μH showed a change in opposite manner to that for nH .

It is clear that the μH decreases with the increasing of Ga content then reaches the maximum value at 18% Ga content for as deposited samples and at 12% Ga content for samples prepared at temperatures of 373 and 473, respectively.

The capacitances at reverse bias voltage of measurements of (GeS2)100-xGax/n-Si,(GeS2)100-xGax/p-Si and (GeS2)100-xGax/p-Ge heterojunctions at frequency (1kHz) showed that both the built–in potential and concentration of charge carriers NB increases while the depletion region decrease with the increasing of substrate temperatures and Ga content.

The current–voltage characteristics of heterojunctions show that the forward current at dark condition varies approximately exponentially with applied voltage and the junctions are coinciding with recombination–tunneling model.I-V characteristics under illumination showed that the heterojunctions prepared from (GeS2)100-xGax on the basis of n-Si have a high efficiency as the Ga content and substrate temperatures increase.

The junctions prepared on the basis of p-Ge, showed high efficiency with the increasing of substrate temperatures while they are showing a decrease in efficiency with increasing the Gallium content.

The efficiency of junctions were improved for (GeS2)100-xGax prepared with thickness ≈50 nm at room temperature on different substrates (p-Si ,n-Si and p-Ge).

Optical properties (energy gap and optical constants) of (GeS2)100-xGax films with thickness of ≈ 50 deposited at room temperature with different gallium content have studied.

It was found that the optical energy gap are wide and exceeded that for samples with higher thickness , also Eg opt showed decrease with increase of content x .

The electrical measurements included (I-V) and (C-V) showed that the junctions p-GeS2/n-Si, p(GeS2)94Ga6/n-Si and p-(GeS2)88Ga12/n-Si were the best as solar cells

Main Subjects

Physics

No. of Pages

120

Table of Contents

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Language

English

Data Type

Arab Theses

Record ID

BIM-607730