My main research line is the development of high efficiency multijunction solar cells. In my PhD at the Instituto de Energía Solar (IES-UPM) I achieved a world record efficiency of photovoltaic conversion of GaInP/GaAs solar cells (2009, published in Applied Physics Letters, DOI: 10.1063/1.3078817, and in the Best Research Cell Efficiency Chart), and I obtained a PhD Award by UPM (2010). I worked in several projects with national and international companies (such as ISOFOTON, ABENGOA, SEMPRIUS, etc) for the transfer of this technology to the industry. To progress in the development and realization of the potential of these solar cells I was granted funding from the Fulbright and Marie Curie IOF programs for postdoctoral research at the National Renewable Energy Laboratory (NREL, Colorado, USA) from 2012 to 2015, to develop metamorphic multijunction solar cells. My work was key in the impressive progress of this technology and led to coauthoring in more than 25 publications in high impact JCR journals. I returned to IES-UPM in March 2015 to complete the return phase of my Marie Curie IOF project, successfully transferring this technology to IES-UPM in the following years and achieving a Ramon y Cajal award in 2016. Besides, this research line has provided an exceptional framework for the formation of my PhD student Manuel Hinojosa (defending January 2022) in the development of high efficiency solar cells, with emphasis in epitaxy technology. In addition, the characterization and theoretical analysis I brought from NREL and further developed at IES-UPM also constituted a large fraction of PhD student Iván Lombardero’s Thesis (2020, UPM Thesis Award, now Project Manager at Qualifying Photovoltaics). Another remarkable achievement was starting a collaboration with Dr. Ripalda from INM-CSIC to enhance the models I developed at NREL to estimate the energy production of multijunction solar cells by using machine learning methods, with several oral contributions to conferences and a paper published in Nature Communications (DOI: 10.1038/s41467-018-07431-3). I continue a close collaboration with NREL, including a 2-month research stay in 2018, which led to coauthoring in the presentation of the highest photovoltaic conversion efficiency, and a 3-month pre-doctoral stay by M. Hinojosa in 2019. Most of this work was funded through RETOS (TEC2014-54260-C3-1-P) Project and a private contract with IBERDROLA (see C.2).

Since March 2021 I am Associate Professor (Profesor Contratado Doctor I3). I perseverate on the development of high efficiency solar cells but now focusing on the achievement of virtual substrates for defect-free and low-cost fabrication of high efficiency structures, with funding from “Plan Estatal I+D RETOS” as co-IP in project RTI2018-094291-B-I00 and private contracts with companies IQE (UK) and UMICORE (Belgium) (see C.3.). This line of research has led to a collaboration with Prof. Pere Roca at LPCIM/Ecole Polytechnique since 2020, using a new type of Ge/Si virtual substrates. Besides, I have started a research line to develop and incorporate embedded porous silicon layers to these virtual substrates, aiming to achieve detachable and crack-free epitaxial layers to obtain lightweight, flexible and cost-effective high efficiency solar cells. This work is fund