121.1report

8/17/2019 121.1report

1/3

Catibog, J.M.R., Mercado, A.R.T., See, A.J.G.. (2016)Page 1 of 3

Photovoltaic Effect of Copper Photovoltaic Cells

Catibog, J.M.R., Mercado, A.R.T., See, A.J.G.Department of Mining, Metallurgical, and Materials Engineering

University of the Philippines

Diliman, Quezon City, Philippines [email protected], [email protected],[email protected]

Abstract —Semiconductors are materials that are of

intermediate resistivity. They are used in numerous applications

including electricity production. An example of a semiconductor

system with this ability is the photovoltaic (PV) cell, which

utilizes the photovoltaic effect to convert solar to electrical

energy. The main objective of this experiment is to replicate the

photovoltaic effect on copper PV cells. Two cleaned and polished

copper sheets were used wherein one was heated for oxidation to

occur. The sheets were submerged in salt water. Set-ups of

different salt content were used to determine the effect of salt

solution on the amount of current produced. The clean copper

strip and the copper oxide-coated strip were used as the positive

and negative terminals, respectively. Afterwards, current

readings of each cell when exposed to sunlight and artificial light

were obtained. The produced copper PV cells were able to

produce current. It was also found that the current increases

when salt concentration is increased while solar light producesmore current than artificial light.

Index Terms — Semiconductors, Photovoltaic Cells, Photovoltaic

Effect, Copper PV cells

I. I NTRODUCTION

Semiconductors are materials that are neither good

insulators nor good conductors. Their resistivity is of

intermediate value at 10-3

to 106 !-cm and highly dependent on

temperature [1]. They may either be intrinsic, in which

semiconductivity is inherent in the pure material, or extrinsic

wherein impurity atoms or dopants dictate the electrical

properties. Extrinsic semiconductors are further divided into

two: n-type and p-type, derived through introduction of excess

electrons or holes, respectively [2].

One of the earliest materials found to have semiconductor

properties is copper oxide. The discovery occurred even before

the emergence of silicon devices. Specifically, they show p-

type conductivity [3].When a single semiconductor crystal is doped with

acceptor-type impurities on one side and donor-type impurities,

p-n junction is formed. An illustration is shown in Figure 1.

Since a large amount of holes are present in the P-region, they

diffuse towards the N-region where density of holes is small.

Similarly, the electrons from the N-region diffuse towards the

N-region. Because of this, electric current flows from the P-

region to the N-region across the junction despite the absence

of an initial electric field [4]. At thermal equilibrium, a

depletion region is formed when diffusion of the charge

carriers stop. A wall separating the two regions is formed

wherein electrons are immobile at the P-side and holes are

immobile at the N-side [5].

Fig. 1. P-n junction(Godse, Atul P., Uday A. Bakshi, and Ajay V. Bakshi. Electron

Devices.)

P-n juctions may be used to harvest energy. One way to dothis is through a thermoelectric generator wherein temperature

gradient is converted into electrical energy [6]. A more widely

used device is the photovoltaic cell. It utilizes the photovoltaic

effect wherein solar energy is converted to electricity. When

the depletion region is formed as shown in Figure 1, light

absorption in either p or n regions cause generation of charge

carriers. The excess holes formed at the junction are able to

lower their energy by moving from the N-region to the P-

region while excess electrons move the opposite way. The

potential difference at the junction causes an electric current,

which can be used to produce electricity [7].

Photovoltaic systems are currently used as source of energy

not only in commercial set-ups but also for space applicationsand marine time navigation and in telecommunications. They

are also used for cathodic protection wherein the externally-

applied counteracting current makes a metal cathodic, and

therefore corrosion-resistant [8].

The main objective of this experiment is to create a

photovoltaic cell and replicate the photovoltaic effect using

copper oxide submerged in salt solution. It also aims to

differentiate the effect of the salt concentration as well as the

type of light used on the amount of current produced of the

photovoltaic cell.

8/17/2019 121.1report

2/3


II.

METHODOLOGY

From a copper sheet, copper strips were obtained. The said

strips were then cleaned, first with soap to remove all dirt and

were further cleaned using sandpaper with 180 grit size to get

rid of possible traces of corrosion. The copper strips were

ensured to be clean since any trace of dirt or corrosion might

affect the properties of the strip, moreover, it might cause side

reactions in the later part of the study.After cleaning, one strip was heated using a hot plate at its

highest setting, while the other strip was set aside. The strip on

the hot plate was allowed to heat up until a thick black coating

was formed at its surface. Once the strip was covered with the

said coating, the hot plate was turned off and the heated

copper strip was slowly cooled. Black coatings from the

surface of copper strip were scraped off; this procedure was

done carefully to avoid damaging the oxide layer formed at

the surface.

Fig. 2. Copper Strip Oxidation Setup

The copper strips were then placed together in a 250mL

beaker; it was made sure that the strips will not touch together.

Afterwards, desired concentration of saltwater was prepared by

adding 10 mL water and varying amounts of salt. Saltwater

was then poured in the beaker together with the copper strips.

The purpose of saltwater addition is that it acted as the bridgeor connection between the two copper strips that will later on

act as cathode and anode. Clean copper strip was connected to

the positive terminal of meter via alligator clips while the

copper-oxide strip was connected to the negative terminal.

Afterwards, an artificial light was radiated to the assembled

photovoltaic cell and reading from the meter was recorded.

Then, the cell was placed outdoors facing the sun (solar light),

meter was also obtained. All obtained data were tabulated, and

were then analyzed-determining the relationships of the

different parameters, such as: which parameters affect the

amount of current.

Fig. 1. Assembled Photovoltaic Cell (Artificial Light)

III.

R ESULTS A ND DISCUSSION

The artificial photovoltaic cells (copper sheets) were

submerged in the salt solution and were exposed to both

artificial and solar light. The table below shows the current

readings of the same copper sheet in different salt solution

concentrations. It can be observed that as the concentration of

salt solution increases, the recorded current also increases.

Furthermore, comparing the current recoded under the naturallight and the artificial light, it can be observed that the current

induced by the photovoltaic cell under the sunlight is

significantly larger than that of the artificial light by around

5%.

TABLE I. CURRENT R EADING IN ARTIFICIAL AND NATURAL LIGHTFOR PHOTOVOLTAIC CELLS UNDER DIFFERENT CONCENTRATIONS OF

SALT SOLUTION

Salt

(g)Water(L)

Salt

(mol)

Concentration

(M)

Artificial

Light

(!A)

Sunlight

(!A)

5 0.01 0.085558 8.55578371 56.4 608

10 0.01 0.171116 17.11156742 132.5 686

15 0.01 0.256674 25.66735113 146.9 700

20 0.01 0.342231 34.22313484 165.7 754

25 0.01 0.427789 42.77891855 204 789

30 0.01 0.513347 51.33470226 275 790

Based on the table above, it can also be concluded that the

copper sheets used as solar cells can still emit an ample

amount of current even under an artificial light (incandescent

and fluorescent lamp). Sunlight’s and incandescent lamp’s

spectrum do not differ much since they are both categorized to

have continuous spectrum as shown in the figures below,

though the light emitted by the sun is much brighter in color

compared to that of the incandescent lamp. The amount of

current generated by the solar cell is affected by the intensity

and wavelength of the light it was exposed to, thus the

recorded current for the solar cells under sunlight are higher

than that of the artificial light since sunlight has higher

intensity than any artificial light because of the presence of

UV and gamma rays. [9]

Fig. 3. Incandescent VS Sunlight Spectrum(http://www.chemistryland.com/CHM107Lab/Exp7/Spectroscope/

Spectroscope.html)

The current and voltage reading depends on the light

absorbed and the surface condition of the photovoltaic cell.

8/17/2019 121.1report

3/3


More accurate higher readings will be obtained if the solar

cells are exposed to direct light without any shade or

hindrance. There is also a need for a clean surface for the light

to interact with the cell. Accumulation of contaminants on the

surface of the cell will extremely affect its efficiency. [10]

Photovoltaic cells can be characterized as thin-film or

crystalline type. Thin-films are less expensive compared to the

bulk/crystalline type. On the other hand, though crystalline-

type photovoltaic cells are costly than the thin-film ones, they

are most efficient in converting renewable energy. The table

below summarizes in detail the advantages and disadvantages

of each type of photovoltaic cells. [11]

TABLE II. CRYSTALLINE AND THIN-FILM SOLAR CELLS

(http://www.ni.com/white-paper/7229/en/)

IV. CONCLUSION

Artificial photovoltaic cell made from copper strip, oxidized

copper strip and saltwater solution were able to produce

current. Furthermore, relationships among the parameters were

established wherein, it is observed that increasing the saltsolution also increases the current produced. Add to that,

comparing the two light sources, solar light produces more

current as compared to artificial light.

V. R EFERENCES

[1] Balkanski, Minko, and R. F. Wallis. Semiconductor

Physics and Applications. Oxford: Oxford University

Press, 2000.

[2]

Callister, William D. Materials Science and Engineering:

An Introduction. New York: John Wiley & Sons, 2007.

[3] Barquinha, Pedro. Transparent Oxide Electronics: From

Materials to Devices. Chichester, West Sussex: Wiley,

2012.

[4] Achuthan, M. K., and K. N. Bhat. Fundamentals of

Semiconductor Devices. New Delhi: Tata McGraw-Hill,

2007.

[5] Godse, Atul P., Uday A. Bakshi, and Ajay V. Bakshi.

Electron Devices. Pune, India: Technical Publications

Pune, 2007.

[6] Sazonov, Edward, and Michael R. Neuman. Wearable

Sensors: Fundamentals, Implementation and Applications .

[7] Besançon, Robert M. The Encyclopedia of Physics. New

York: Van Nostrand Reinhold, 1974.

[8] Wenham, S. R. Applied Photovoltaics. London:

Earthscan, 2007.

[9] Knier, Gil. "How Do Photovoltaics Work?" - NASA

Science. Web. 20 Mar. 2016.

[10] "6 Ways to Improve Solar Cell

Efficiency." DoItYourself.com. Web. 20 Mar. 2016.

[11] "Part I – Photovoltaic Cell Overview." - National

Instruments . 4 Dec. 2009. Web. 20 Mar. 2016.

Documents

121.1report