• “Low-cost solar cells with nanocomposites of TiO2 and CuInSe2 obtained with electrodeposition”. Autores: Matías Valdes, Alejandra Frontini, Marcela Vazquez, and

VALDES, MATÍAS; FRONTINI, MARÍA ALEJANDRA; VAZQUEZ, MARCELA; GOOSSENS, ALBERT

San Carlos de Bariloche, Argentina

Congreso; Sólidos 06; 2006

CNEA

Low-cost solar cells with nanocomposites of TiO2 and CuInSe2 obtained with electrodeposition Matías Valdes1, 2, Alejandra Frontini1, Marcela Vazquez1, Albert Goossens2 1 División Corrosión INTEMA Universidad Nacional de Mar del Plata - CONICET,  J. B. Justo 4302, B7608FDQ Mar del Plata, Argentina.  2 Opto-electronic Materials, Faculty of Applied Sciences, Delft University of Technology Julianalaan 136, 2628 BL Delft, The Netherlands.                   In order to reduce the production cost of solar cells, new architectures based on nanomaterials need to be developed. Towards this end we prepared nanoporous TiO2 and filled the pores with CuInSe2 using electrodeposition. Titanium dioxide is an n-type wide bandgap semiconductor. CuInSe2 is a p-type semiconductor with a direct bandgap of 1.0 eV. When CuInSe2 is applied onto TiO2 a pn junction is formed by which sunlight can be converted into electricity. In a nanocomposite of TiO2 and CuInSe2 the pn junction is distributed in space, which allows reduction of the minority carrier diffusion length down to a few tens of nanometers.                 Thin CuInSe2 films have been prepared by electrodeposition from a single bath solution on both dense and nanoporous TiO2. The films have been deposited potentiostatically using a deareated electrolyte at different potentials. Also the deposition time, temperature, and solution composition have been varied.     The effect of annealing in air and in argon at different temperatures and times is also investigated.                 Thin films and nanocomposites of TiO2 and CuInSe2 have been studied with electron microscopy, X-ray Raman, and optical absorption spectroscopy. Indeed after a thermal anneal in Ar at 400OC for 30 minutes the quality of CuInSe2 is excellent. In particular the nominal crystal structure and the bandgap of 1.0 eV are found.                 Although pinholes are found occasionally, good samples with diode curves showing a rectification ratio at ± 1 V of 100. Upon irradiation with simulated solar light of 1000 W m-2 a clear photoconductivity response is obtained. Furthermore, also photovoltaic energy conversion is found in TiO2 | CuInSe2 nanocomposites. Although the conversion efficiency needs improvement, this result is without precedent and encourages us to elaborate on this new solar cell concept. Most likely the efficiency is limited by fast electron-hole recombination at the TiO2 | CuInSe2 interface, which can be suppressed by applying a so-called buffer film at the interface. The role of this buffer film is to aid the electron injection process by matching the conduction bands and suppressing the backflow of electrons.                  Current investigations are focussed on electrodeposition of buffer films and on further optimisation of the thermal anneal in a controlled environment. Indeed, a new horizon for solar cell science and technology will be offered when electrodeposited solar cells enter the market.