Up-conversion emission of aluminosilicate and titania films doped with Er3+/Yb3+ by ion implantation and sol-gel solution doping

A key challenge in second generation solar cell development is to overcome major energy losses and to obtain high efficiency homogeneous films. In order to take advantage of the major portion of the solar spectrum, minimizing transparency losses, the use of frequency converting phosphors is a promising solution. From this viewpoint, the development of up-conversion (UC) materials for improving the light harvesting efficiency is a demanding task. Here, we report a low cost sol-gel (SG) spin-coating deposition technique which allows scalability to deposit SiO2 - Al2O3 and TiO2 films doped with the Erbium/Ytterbium lanthanide pair to obtain functional coatings with efficient near-infrared (NIR) to visible UC photoluminescence (PL) at room temperature. An alternative direct incorporation of the lanthanide ions into the solar cell material was also achieved by ion implantation. Comparison of both methods indicates that, although ion implantation is an accurate and controllable doping method, UC emission is superior at present from the films obtained by solution doping. However, this is the first time, to the best of the authors' knowledge, that UC properties have been studied for the Er/Yb pair in this system by this route. Therefore, the results reported here provide an additional approach for better understanding the doping parameters needed to obtain high PL performance.