题目：Upconversion Photovoltaics: Challenges and Possible Solutions from Nanophotonics
Upconversion (UC) constitutes a third-generation solar cell technology where the solar spectrum is re-shaped using optical materials in order to match the solar cell absorbance. The mechanism of UC consists of the production of one high-energy photon from the addition of two low-energy photons. This approach has the advantage that it enables the profit of a large quantity of energy of the solar spectrum that would normally be lost by transmission. These losses represent 20% of the total solar spectrum for crystalline silicon cells, and they are even larger in the case of other technologies with semiconductors with higher bandgaps. Moreover, because UC materials do not require electronic-grade purity, their cost can be low. However, UC presents different challenges that have to be overcome in order to obtain efficient devices. Moreover, UC is a non-linear optical effect that requires high power concentration. In this talk we review the state-of-art of upconversion photovoltaics, materials, mechanisms and its characterization. Next, the implementation of UC layers in solar cells will be discussed. Finally, some technologies from nanophotonics, such as the use of spectral concentration by quantum dots, plasmonic resonators or photonic crystals, shall be analyzed as possible candidates to overcome some of the challenges that UC materials present.
Jose Marques-Hueso is an assistant professor at Institute of Sensors, Signals and Systems (ISSS), Heriot-Watt University. His research focuses on the use of functional materials for optoelectronic devices, sensors and additive manufacturing. He completed MSc in physics from the University of Valencia (Spain) in 2005, and he completed his PhD in the Optoelectronic Materials and Devices Group (Materials Institute, Uni. Valencia) in 2011. He has published over 40 journals and conferences papers, 2 book chapters and holds an international patent on nanofabrication.