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

Abstract

Tin(II) sulfide (SnS) is a promising low cost photovoltaic material due to its favorable direct optical band gap (∼1.3 eV) and high absorption coefficient (>10⁴ 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 °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 In₂S₃ as a buffer layer.