Enhancing photovoltaic performance of silicon solar cells by rare earth doped glass ceramic

The efficiency of semiconductor solar cells may be improved by inserting in the front or rear of the solar cell an optically active layer doped with rare earth ions which acts as "down-converter" (DC) or" up-converter "(UC). This is just one of the possibilities that involve several structures and geometries such as waveguide configuration and radiation trapping systems. Among these systems glass ceramics play a crucial role especially because they combine the optical properties of glasses with the spectroscopic properties of the crystals activated by luminescent species. In this work we will give a short review regarding the research already performed by the team in the field of down-conversion process. We will focus the attemption on the cooperative energy transfer between donor and acceptor ions taking as example the interaction among one Tb3+ ion and two Yb3+ ions allowing to cut one high energy photon at wavelength shorter than 488 nm into two low energy photons around 980 nm. The choice of the matrix is another crucial point to obtain an efficient down conversion processes with rare earth ions; we demonstrated that the Tb3+/Yb3+ energy transfer efficiency in a 70SiO2-30HfO2 glass-ceramic waveguide is effective.