Study of Optical Properties of Zinc Oxide Nanostructures Thin Solid Films Using Spin Coating Technique: APrecursor Organic for Electronics Devices Applications

In this research work we synthesized Zinc oxide [ZnO] Nanostructures using plant extracts. Zinc oxide [ZnO] nanostructures were synthesized by solution method and deposited by spincoating technique. The samples were characterized by UV-Vis spectrophotometer and Fourier-transform infrared spectroscopy (FTIR).The maximum absorption peaks occurred at 235.0 nm, 250.0 nm, 270.0 nm, and 300.0 nm respectively but lower when compared with the bulk size that occurred at 350.0 nm and in the visible spectrum of the wave length band. Band gap energy of zinc oxide nanostructures at 500.0 rpm was 3.8 eV. FTIR spectrum was recorded in the range of 4000.0 cm-1 to 500.0 cm1. FTIR Observation shows that the bands of ZnO Nanostructures occur at 3903.4 cm1, 2802.2 cm-1, 2195.9 cm-1, 1963.2 cm-1, 1834.5 cm-1, 1194.7 cm-1, and 682.6 cm-1. The synthesis ZnO Nanostructures FTIR results how ZnO functional group was found at low wave number. The result can be used for performance enhancement of solar cell and to develop guide line for fabrication of organic solar cells.


Introduction
The branch of technology that studies different materials at a nanometric scale is referred to as nanotechnology and it is also defined as science of production, manipulation and use of materials at subatomic level that find sits application in materials science, engineering, and electronics. Recently, transparent conducting oxides (TCOs) have been widely studied. ZnO thin solid films are one of the most prominent transparent conducting oxides for the fabrication of the next generation advanced applications such as window layer in heterojunction solar cells ZnO is an inorganic material with high electron mobility and easy to prepare as electron acceptor to dissociate excitons formed in conjugated polymer as the active material of solar cells. Zinc oxide is an inorganic material that has found it suspension many applications and can be prepared as a nanostructure [1][2][3][4][5][6][7][8][9][10]. Zinc oxide nanostructures have been widely used as donor material due to its superior optoelectronic properties and it is relatively easy to be synthesized by using the following methods: ultrasound, anodization, co-precipitation, solgel method, chemical vapor deposition and mechano-chemical activation thermal synthesis. Ramesh, et al., in their research reported that the synthesized ZnO nanostructures are moderately stable, roughly spherical with maximum particles in size range with in nm in diameter [10].  [14]. Zinc oxide nanostructures have been widely developed as donor material due to its superior optoelectronic properties and it is relatively easy to be synthesized by using solution methods. Taufiq, et al., used a sol-gel method to synthesis and study ZnO Nanostructures [15]. Fakhari, et al., carried out green synthesis of nanostructures by biological systems they reported peaks absorption around 350.0 nm due to large excitation binding energy at room temperature≈23.0 °C [16].

Laboratory Instruments and Materials
The materials used were bashful leaves (Mimosa Pudica). The leaves are bipinnately compound, with one or two pinnae pairs, and

Substrates Cleaning Procedure
The cleaning procedure for soda-lime glass substrates is explained in the following lines:

Synthesis of Zinc Oxide Nanostructures
In this procedure 0.

Analysis of the Samples
The materials were analyzed using a UV-VIS spectrophotometer

Deposition of Synthesized of Zinc Oxide Nanostructures
Zinc oxide solution was prepared and deposited onsoda-lime glass substrate at different spin coating speed using spinning coating (model The Process Station Etching, SPS-Europe B.V., Netherlands).
Spin coating is one of the most common techniques for applying thin films to substrates (Figure 1). It is used in a wide variety of industries and technology sectors. The advantage of spin coating is its ability to quickly and easily produce very uniform thin solid films, ranging from a few nanometers to a few microns in thickness.
The use of spin coating in organic electronics and nanotechnology is widespread and has built upon many of the techniques used in other semiconductor industries. It also has some differences due to the relatively thin solid films and high uniformity required for effective device preparation, as well as the need for self-assembly and organization to occur during the casting process. Spin coating speeds of 3000 revolution per minute (rpm), 2000 rpm, 1500 rpm, 1000 rpm, 750 rpm, and 500 rpm were considered respectively for 2 log(% ) . .
where A is the absorbance, %T is the percentage transmittance.
The following relational expression proposed by Tauc, Davis, and Mott is used: The value of the exponent n denotes the nature of the sample transition. For direct allowed transition where (hʋ) is the photon energy the values were determined from the inverse relationship between energy in electron volts [eV] and wavelength of the UV-visible spectrum using the equation (5).
where E is the photon energy, h is planck's constant (6.626× The energy band gap was obtained from straight line plot of (αhʋ) 2 vs. hʋ by extrapolating of the line to baseline. The absorption coefficient (α) of thin film was calculated using the equation (6) [22].

2.3
FTIR spectrum of ZnO nanostructures was obtained from sample deposited at 500 rpm corresponding to 120 nm thickness. the absorption spectrum of the ZnO nanostructures that were made to 500 rpm lies at 230 nm to 300 nm in UV spectrum of wavelength band in agreement as reported by Gupta, et al., [23]. The maximum absorption peaks occurred at 230 nm, 250 nm, 270 nm, and 300 nm respectively but lower when compared with the bulk size that occurred at 350 nm and in the visible spectrum of the wavelength band. Figure 5 shows band gap energy graph of zinc oxide nanostructures at 500 rpm, the obtained band gap energy was 3.8 eV which is similar to the research study reported by Taufiq, et al.,

UV-Vis Spectra Analysis of Zinc Oxide Nanostructures
and Preethi, et al., [15,24]. This shows thickness of plant extract and ZnO nanostructures composites has effect on photon energy absorption.

Conclusion
The research of this scientific work focuses on the ZnO nanostructures thin solid films based on UV-Vis and FTIR spectrums analysis. UV-Vis spectrum analysis shows ZnO nanostructures thin solid film has arrange of absorption that occurs from 235 nm to 300 nm and 350 nm upward invisible spectrums. The synthesis ZnO nanostructures FTIR result shows Zn-O functional group was found at low wave number similar to results reported [7,11,15,[33][34][35][36][37][38][39][40]. The main result of this research work can be used to develop guideline for fabrication of solar cells for performance enhancement. It should be noted that future research will be done in order to improve, further refine and understand the full performance of this material.