Influence of etching parameters on optoelectronic properties of c-Si/porous silicon heterojunction – application to solar cells

Laboratoire de Microscopie Electronique & Sciences des Matériaux (LME&SM), Université des Sciences et de la Technologie d’Oran (USTO), BP 1505, El MNaouer, 31100 Oran, Algeria

^a e-mail: FatihaBechiri@gmail.com

Received: 23 April 2012
Revised: 30 September 2012
Accepted: 15 January 2013
Published online: 8 March 2013

Abstract

Thin layers of nanoporous silicon PS were synthesized by anodic etching, in order to develop photovoltaic cells. We proposed a diluted concentration of hydrofluoric acid with different etching current densities (1, 3, 5 mA/cm²) on a fairly short time anodization. Observations by scanning electron microscope, electrical measurements and optical measurements revealed that the structural properties of PS layers depended on strong conditions of prints. The reverse and forward component of the I-V characteristics showed an appropriate method to explore and extract the parameters of the diode ideality factor n. The optimum conditions of formation of PS were: HF concentration of 1% and an etching current density of mA/cm². Unlike silicon, which has a low absorption of short visible wavelengths, it was shown that the PS had wide energy gap of ≈ 2 eV, and a marked improvement in the absorption between 400 and 600 nm. This property has been used to optimize the response of the solar cell Ni/PS/c-Si. Efficiency performance close to 4.2% was obtained with a V_oc of 400 mV, and fill factor of 46%. The solar cell exhibited better response than the reference cell Ni/c-Si. These results show that PS/c-Si heterojunction has a potential for photovoltaic applications.