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UID:69d255c7b3216
DTSTART:20230927T140000Z
SEQUENCE:0
TRANSP:OPAQUE
LOCATION:ICFO Elements room
SUMMARY:ICFO | CATARINA FERREIRA
CLASS:PUBLIC
DESCRIPTION:To mitigate the present environmental crisis\, caused by the ex
 cessive use of fossil fuels and associated release of carbon dioxide into 
 the atmosphere\, it is necessary to significantly reduce worldwide energy 
 consumption\, to rely more strongly on clean and renewable sources of ener
 gy\, but also to maximize energy efficiency in currently existent technolo
 gies that make use of energy. To reach such maximal energy efficiency\, it
  is necessary to optimize light propagation\, harvesting\, and utilization
  in the different existent optoelectronic technologies. Given that a consi
 derable portion of the global energy consumption is dedicated to illuminat
 ion or devices incorporating illumination sources in them\, a clear path t
 o maximize energy-efficiency would imply minimizing the light losses in su
 ch kind of systems. In addition\, for maximal energy conversion efficiency
  it is essential to optimize light absorption in systems that perform an u
 nassisted sunlight transformation into other forms of energy\, such as ele
 ctrical or chemical.\nTo reach the double goal of optimizing light utiliza
 tion and transformation\, in this thesis we consider the study of optical 
 ergodic configurations\, where light rays are randomized after a few bounc
 es at the interfaces\, losing any correlation with the external incident s
 tate and giving rise to an isotropic radiation inside the material. In Cha
 pter 2 of the thesis\, we demonstrate that an ergodic geometry can be used
  to obtain homogeneously distributed polarized light emission. In the same
  ergodic system\, we also demonstrate that the light with the unwanted pol
 arization can be trapped and transformed back into electricity by using a 
 couple of perovskite solar cells. Such features are potentially useful to 
 increase energy efficiency in optoelectronic devices incorporating illumin
 ation sources in them\, as is the case of liquid crystal displays. A simil
 ar ergodic light propagation is also considered in Chapter 3 to determine 
 what the maximal light trapping and effective light absorption is in a BiV
 O4-based photoanode of a photoelectrochemical cell used for light transfor
 mation into hydrogen. The limits in the efficiency of such energy transfor
 mation are seen to be strongly linked to the weakly light-absorbing sub-ba
 ndgap states. A three-dimensional nano-structuration of the photoanode in 
 the photoelectrochemical cell is explored as a path to eventually reach er
 godicity for light propagation in the photoanode. In the final chapter of 
 the thesis\, we consider a tandem construction of two complementary light 
 absorption elements\, such as a BiVO4 photoanode and an organic solar cell
 \, to obtain an unassisted conversion of sunlight into hydrogen in photoel
 ectrochemical cells. Optical multilayers designed by implementing an inver
 se problem-solving approach are found to be an essential ingredient to pro
 perly balance light absorption among such two light-absorbing elements in 
 the tandem\, leading to an optimal solar-to-hydrogen conversion.\n&nbsp\;\
 nThesis Director: Prof Dr. Jordi Martorell\n&nbsp\;
DTSTAMP:20260405T122959Z
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