1. Microenergy Sources and Sensor Integration group, Institute of Microelectronics of Barcelona (IMB-CNM-CSIC),Barcelona,Spain
2. Instituto Nacional de Astrofisica, Óptica y Electrónica (INAOE),Electronics Department,Puebla,México
3. Swiss Nanoscience Institute, University of Basel,Basel,Switzerland
4. Catalonia Institute for Energy Research (IREC),Department of Advanced Materials for Energy Applications,Barcelona,Spain