Magnetron sputtered Cu doped SnS thin films for improved photoelectrochemical and heterojunction solar cells

Tin(II) sulfide (SnS) is a promising low cost photovoltaic material due to its favorable direct optical band gap (similar to 1.3 eV) and high absorption coefficient (>10(4) cm(-1)). However, SnS solar cells are reported to have low efficiency due to band misalignment that can be reduced by the proper optimization of acceptor concentration in p-SnS. This work describes the effect of extrinsic Cu doping in sprayed SnS thin films on SnO2:F glass for a possible enhancement in the photocurrent in photoelectrochemical cells and the open circuit voltage in heterojunction solar cells. The structural, morphological, optical and photoelectrochemical properties of the Cu:SnS films are studied in detail. A process temperature of 325 degrees C was found to be optimum for Cu doping at the Sn vacancies in the host lattice. An improvement in the photocurrent density from 1.1 mA cm (2) to 1.8 mA cm (2) was observed in the photoelectrochemical cell prepared by this doping process. A further enhancement in photocurrent of up to 3.2 mA cm(-2) was shown when the residual surface Cu was removed by HCl etching. The developed Cu:SnS heterojunction solar cell showed a record open circuit voltage of 462 mV with ln(2)S(3) as a buffer layer.