Calcium-stannous oxide solid solutions for solar devices

In this study, solid solutions formed of SnO and CaO [termed (Sn:Ca)xO] are explored as potential solar active layers. The results indicate that a ratio of x = 7 : 1 leads to a fundamental direct bandgap of 1.56 eV. In order to promote the transport of excited charge carriers from within the active layer, appropriately aligned hole/electron transport layers need to be identified. To this end, a set of results are presented for the electronic band alignment of (Sn:Ca)7:1O with a selection of oxide transport layers, with and without oxygen vacancies. From this, it is recommended that a CaO/(Sn:Ca)7:1O/TiO2 device shows the most potential for an all-oxide solar cell.