Abstract
Annealing treatment of transparent conducting oxide (TCO) thin films plays a great role in enhancing the optoelectronic properties of the material. Changes in morphological, optical and electrical properties of indium tin oxide (ITO) thin films deposited by RF sputtering were investigated after exposing the films to Nd:YAG laser radiation. ITO thin films of 158 nm thickness were irradiated with different laser energy; 25 mJ, 75 mJ, 120 mJ and 165 mJ respectively. Atomic force microscopy (AFM) results reveal a smooth surface morphology and enhance grain size as the laser energy increases. Highest optical transmittance value of 96.5 % at 620 nm wavelength was obtained by film treated with 165 mJ laser energy as determined by UV-Vis spectrophotometer. Electrical resistivity measurements as determined by four-point probe show a significant decrease in resistivity and sheet resistance with respect to increasing laser energies. The ITO films optoelectronics properties were enhanced with the film annealed at 165 mJ exhibiting the highest calculated figure of merit. This laser treatment method has effectively fine turned the ITO films properties toward TCO functional properties required for solar cell application.
Highlights
Incorporation of transparent conducting oxides (TCO) thin layers in silicon (Si) solar cells is one of the progresses so far achieved in the development of photovoltaic devices
A careful study of these images in Fig. 1 and Table 1 indicates the dependance of indium tin oxide (ITO) films surface morphology on the amount of laser energy exposed on their respective surfaces
Laser annealing treatment of ITO thin films by Neodymium-doped Yttrium Aluminium Garnet (Nd):YAG laser system has been investigated as an approach to improve the ITO optoelectronics properties
Summary
Incorporation of transparent conducting oxides (TCO) thin layers in silicon (Si) solar cells is one of the progresses so far achieved in the development of photovoltaic devices. TCO layers serve as an anti-reflection coating (ARC), junction rectifiers and transparent electrode for the extraction of separated charge carriers from the absorbing region of semiconductor material[1,2,3]. Other applications like organic light-emitting device (LED)[4] and flat panel display (FPD) [5] employed TCO films as transparent conductive contact. ITO thin film is the most widely applied TCO due to its excellent electrical conductivity (104 Ω-1 cm-1) and high optical transmittance (> 80 %) in the visible region of light spectrum[9, 10]. ITO high transparency is as a result of its wide bandgap, whereas the presence of oxygen vacancies and extrinsic defect of tin dopant contributed to its high electrical conductivity [3, 13, 14]
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