Characterization of Cu2S / SnO2: F P-N Junction for Solar Cell Applications
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Date
2019
Authors
Omwoyo, Jared Gisemba
Journal Title
Journal ISSN
Volume Title
Publisher
Kenyatta University
Abstract
Due to industrialization and increase in population, there is need for clean, green and
renewable source of electrical energy. Traditional sources of electrical energy like
fossil fuels are getting depleted, on the other hand silicon based solar cells are
expensive hence the need for low cost and reliable alternative source of energy.
Photovoltaic is a reliable energy source which is renewable. Photovoltaic is a process
of conversion of solar energy to electricity directly using solar cells. For this study
Copper (I) Sulphide (Cu2S) thin films were deposited on glass substrates by Chemical
Bath Deposition (CBD) technique. Copper sulphate (CuSO4) was used as a source of
copper ions, thiourea (CS (NH2)2) as a source of sulphide ions and tartaric acid as a
complexing agent, ammonia solution was used to regulate the pH. SnO2: F thin films
were deposited using spray pyrolysis technique (SPT) on glass substrates at substrate
temperature of 3500 C using pentahydrated stannous chloride (SnCl4∙5H2O) and
ammonium fluoride (NH4F) as precursors. Optical transmittance and reflectance of all
film samples prepared in the range of 200 nm-1100 nm were measured using UVVIS-
NIR spectrophotometer. The optical measurements were simulated using
SCOUT software to obtain optical constants. Cu2S deposited at 0.15 M Cu2+ exhibited
low average transmittance of 20.91 %, high average absorbance of 51.29 % and
narrow optical band gap of 2.33 eV hence a good absorber material to be used as ptype
layer in solar cells applications. On the other hand, SnO2: F had high average
transmittance of 79.94 % and wide optical band gap of 4.04 eV at 4 % concentration
of fluorine. This shows that SnO2: F is a suitable n-type layer for solar cell
applications. Cu2S had lowest refractive index of 1.44 at 0.15 M Cu2+. The four point
probe was used to measure the sheet resistivity of all thin films. SnO2: F had lowest
resistivity of 40.3 Ω cm at 4% concentration of fluorine while Cu2S had low
resistivity of 0.40x103 Ω cm at 0.15 M Cu2+. .The Cu2S/SnO2: F p-n junction was
fabricated in phases. First the n-type layer of SnO2: F was deposited onto the glass
substrate by spray pyrolysis method and then the p-type layer of Cu2S thin films was
deposited onto SnO2: F thin film to form a p-n junction. The solar simulator was used
to measure the I-V characteristics of the fabricated cell. The fabricated cell had open
circuit voltage (Voc) of 0.4075 V, short circuit current (Isc) of 0.00219 A, fill factor
(FF) of 0.61 and efficiency (η) of 0.303 %. Therefore, Cu2S and SnO2: F thin films
are suitable materials for fabrication of Cu2S/SnO2: F p-n junction solar cell.
Description
A Thesis Submitted in Partial Fulfillment of the Requirements for the Award of a Degree of Master of Science (Physics) In the School of Pure and Applied Sciences of Kenyatta University, October, 2019