Colloidal CuInS 2 Based Nanocrystals /TiO 2 Nanotube Arrays Composite Solar Cells Fabrication and Testing
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Colloidal CuInS2 Based Nanocrystals /TiO2 Nanotube Arrays Composite Solar Cells Fabrication and Testing Vanga R. Reddy1, William Wilson1, Rick Eyi1, Jiang Wu1, M. O. Manasreh1, John Dixion2, Andrew Wang2 1
Department of Electrical Engineering, 3217 Bell Engineering Center, University of ArkansasFayetteville, AR 72701, USA 2 Ocean Nanotech, 2143 Worth Ln, Springdale, AR, 72764, U.S.A. ABSTRACT To develop alternative and low cost photovoltaic technologies we have synthesized CuInS2 nanocrystals with tunable optical properties and characterization was carried out thoroughly with TEM, SEM, EDAX and XRD. Furthermore large self-organized arrays of TiO2 nanotubes were fabricated on Ti foil followed by simple electrochemical anodization technique and characterized their structure by SEM and then for the first time coupled both the nanocrystals and nanotubes to form a p-n junction type photovoltaic device. The current-voltage (I-V) characteristics of photovoltaic cells were measured to test the proof of concept. Some preliminary experiments showed that device generates some current upon illumination. However, in our case we fabricated a device without sandwiching any buffer or barrier layers in between nanocrystals and nanotube arrays. We have been optimizing our solar cells efficiency by improving quality of nanotubes and nanocrystals. Some of the interesting finding are presented and discussed. INTRODUCTION At present, large-scale introduction of photovoltaic (PV) solar cells is hindered by the high production costs related to the involved complex technological processes. Alternative materials and new solar cell concepts need to be investigated to develop low-cost PV cells [1- 3]. To search an alternative to silicon recently research have been explored CuInS2 family materials, which seems to be very promising mainly because of theoretical prediction of efficiency about 30-40 % as well as higher absorption coefficient of those materials[2,3].So far mostly thin film deposition or chemical bath deposition based technologies have been developed. However, these techniques also somewhat costly and time consuming. As a further alternative, preparation of nanocrystals in a colloidal form followed by chemical synthesis considered to be an excellent alternative. Due to the developments in surface chemistry it is also possible to anchor CuInS2 nanocrystals to oxide materials surfaces such as TiO2 or ZnO to form thin films for device fabrication purpose. Thus expensive deposition methods can be prevented. So in recent years there is a renewed interest again to develop large quantities of ternary nanocrystals for photovoltaic applications. In this regard CuInS2 based nanocrystal synthesis is of paramount of interest and these materials are gaining much attention worldwide as alternative nontoxic colloidal materials as compared to CdS or CdSe quantum dots [4, 5]. As a matter of fact, these colloidal materials have high demand in the present photovoltaic market due to their proven ability as a absorbers in solid state solar cells or nan
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