Nanostructure Cu2ZnSnS4 thin film prepared by sol–gel for optoelectronic applications

doi:10.1016/j.solener.2011.07.012

Solar Energy

Volume 85, Issue 10, October 2011, Pages 2518-2523

https://doi.org/10.1016/j.solener.2011.07.012 Get rights and content

Abstract

Thin film of Cu₂ZnSnS₄ (CZTS) has been successfully deposited by sol–gel technique on n-type silicon and glass substrates to fabricate a heterojunction photodiode. The structural properties of the film were investigated by atomic force microscopy. The AFM image of the Cu₂ZnSnS₄ film reveals that the film is a nanostructure material formed from nanoparticles with the particle size of 50–90 nm. The optical band gap, E_g of the Cu₂ZnSnS₄ film was found to be 1.48 eV and the obtained optical band gap suggests that CZTS is very suitable for photovoltaic and optoelectronic applications. The current–voltage characteristics of the Al/n-Si/Cu₂ZnSnS₄/Al diode exhibit a good rectification behavior with ideality factor of 2.84 and barrier height of 0.738 eV. The interface states of the diode were analyzed by series resistance and conductance-voltage methods. The presence of interface states in series resistance–voltage plots was confirmed by the illumination. The interface state density D_it for the diode was found to be 3.63 × 10¹² eV⁻¹ cm⁻². The obtained results indicate that the Al/n-Si/Cu₂ZnSnS₄/Al diode is a photosensor based on controlling of interface states by illumination.

Highlights

► Thin film of Cu₂ZnSnS₄ (CZTS) was successfully prepared by sol–gel method. ► Al/n-Si/Cu₂ZnSnS₄/Al diode exhibits a good rectification behavior. ► Al/n-Si/Cu₂ZnSnS₄/Al diode can be used as a photosensor for electronic applications.

Introduction

Cu₂ZnSnS₄ (CZTS) thin film is one of the promising materials for low-cost thin film solar cell and it exhibits a suitable band-gap energy of 1.4–1.5 eV for solar cells (Ito and Nakazawa, 1988, Jimbo et al., 2007, Moholkar et al., 2011, Rajeshmon et al., 2011).

For cost-effective photovoltaic technology, it is necessary to investigate new materials like Cu₂ZnSnSe₄, Cu₂ZnSnS₄ (Rajeshmon et al., 2011). The constituent elements of CZTS are nontoxic and inexpensive because they are abundant elements in the earth’s crust, although those of CIGS are toxic (Se) and expensive (In and Ga) (Tanaka et al., 2007). The several research groups have been used low-cost deposition techniques such as spray-pyrolysis, photochemical deposition, sol–gel, and electrodeposition for preparation of CZTS films (Scragg et al., 2008, Nakayama and Ito, 1996, Moriya, 2006, Kamoun et al., 2007, Sebastian et al., 2009).

In present study, the sol–gel method was used for preparation CZTS film to fabricate a heterojunction diode, because, this method is a very simple and low-priced process without requiring vacuum system. The CZTS thin film was prepared by the sol–gel method and it is evaluated that the sol–gel method is very simple and inexpensive method for preparing CZTS thin films.

Section snippets

Experimental details

For preparation of Cu₂ZnSnS₄ (CZTS) film, the precursors, copper (II) acetate monohydrate, zinc (II) acetate dihydrate, tin (II) chloride dihydrate, thiourea SC(NH₂)₂, 2-methoxyethanol (2-metho) and monoethanolamine (MEA) were used. The solution of the precursors was dissolved in 2-metho and it was stirred at 45 °C for 1 h to dissolve metal compounds completely. MEA was used as the stabilizer. The CZTS film was prepared using the sol solution dropped onto the silicon and glass substrates rotating

Structural and optical properties of the Cu₂ZnSnS₄ film

The atomic force image of the Cu₂ZnSnS₄ film is shown in Fig. 1. As seen in Fig. 1, the Cu₂ZnSnS₄ film is a nanostructure material formed from nanoparticles. The particle size was determined to be 50–90 nm. The surface roughness of the Cu₂ZnSnS₄ film was determined to be 15.56 nm using a PARK system AFM XEI software programming. For determination of optical band gap of the Cu₂ZnSnS₄ film, we used the following relation (Pankove, 1975): $α h ν = B (h ν - E_{g})^{m}$ where B is an energy-independent constant and E_g

Conclusions

Thin film of Cu₂ZnSnS₄ (CZTS) was prepared by sol–gel technique. The AFM image of the Cu₂ZnSnS₄ film reveals that the film is a nanostructure material formed from nanoparticles with the particle size of 50–90 nm. The obtained optical band gap of 1.48 eV of the film is very suitable for solar cells. Al/n-Si/Cu₂ZnSnS₄/Al diode exhibits a good rectification behavior with ideality factor of 2.84, barrier height of 0.738 eV and the interface state density D_it of 3.63 × 10¹² eV⁻² cm⁻². The obtained results

Acknowledgements

This work was supported by Feyzi AKKAYA Scientific Activates Supporting Fund (FABED) and Global Research Network for Electronic Devices & Biosensors (GRNEDB) and KING Saud University.

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Nanostructure Cu2ZnSnS4 thin film prepared by sol–gel for optoelectronic applications

Abstract

Highlights

Introduction

Section snippets

Experimental details

Structural and optical properties of the Cu2ZnSnS4 film

Conclusions

Acknowledgements

Journal of Non-Crystalline Solids

Solid State Electron

Thin Solid Films

Thin Solid Films

Solar Energy Materials & Solar Cells

Solar Energy

Applied Surface Science

Solar Energy

Electrochemistry Communications

Solar Energy

Nanostructure Cu₂ZnSnS₄ thin film prepared by sol–gel for optoelectronic applications

Structural and optical properties of the Cu₂ZnSnS₄ film