A tandem photovoltaic device includes a first cell and a second cell arranged in tandem. The first cell is configured to receive incident electromagnetic radiation and includes a first charge separating layer having a first semiconducting polymer adapted to create electric charge carriers generated by electromagnetic radiation. A second cell is configured to receive electromagnetic radiation passing out of the first cell in a light propagation path. The second cell includes a second charge separating layer having a second semiconducting polymer adapted to create electric charge carriers generated by electromagnetic radiation. A first titanium oxide layer is interposed between the first and second cells, wherein the first titanium oxide layer is substantially amorphous and has a general formula of TiOx where X being a number of 1 to 1.96.
STATEMENT REGARDING GOVERNMENT SUPPORT
 This invention was made in part during the course of work under grant numbers DE-FG02-06ER46324 from the United States Department of Energy. The United States Government has certain right in this invention.