Abstract
We report a new architecture for high efficiency polymer solar cells introducing a new concept of 'optical spacer' with new material. By implementing a novel solution-based titanium oxide ($TiO_{x}$) layer between the active layer and the electron collecting Al electrode, we invented a way to increase ${\sim}50\;%$ in power conversion efficiency compared to conventional polymer solar cells. Now the new devices exhibit ${\sim}6\;%$ power conversion efficiency, which is the highest value reported to date for a polymer based photovoltaic cell. The $TiO_{x}$ layer increases the efficiency by modifying the spatial distribution of the light intensity inside the device, thereby creating more photogenerated charge carriers in the bulk heterojunction layer.