Nano solar cell integrated within optical nano resonator
Tutor / director / evaluatorVoz Sánchez, Cristóbal
Document typeMaster thesis
Rights accessRestricted access - author's decision
Photovoltaics have developed rapidly over a past decade. In the end of 2013, the total of solar PV global capacity reached 139 GW. The fast development of solar photovoltaic is mainly due to the improvement of solar cell efficiency and the decrease of the costs. The absolute cost of photovoltaic depends on the technology. The photovoltaic market is currently dominated by crystalline silicon. For crystalline silicon photovoltaic, the material cost represents 40% of the total module cost. On the other hand, the emerging technologies of photovoltaic require expensive and scarce materials. Hence, it is necessary to reduce the usage of raw materials in order to decline the cost of solar photovoltaic. One solution to save raw material is reducing the thickness of absorber solar cell. However, reducing the thickness of active layer could compromise the optical absorption. The main focus in this work is to develop nano solar cell integrated within optical nano resonator which is in the main frame of the PhD thesis work of Proise (Study and Realisation of Micro/Nano Photovoltaic Cells and Their Concentration Systems). Proise developed the simulation of the geometry of nano-resonator solar cell in order to optimise the absorber thickness while keeping a good absorption. Based on Proise’s result, the geometry of nanoresonator solar cell with a thickness of 350 nm, a width of 100 nm, and a period of 400 nm is decided to be fabricated. The semiconductor materials used in this work are based on III-V semiconductors, Indium Phosphide (InP) and InGaAs. InGaAs is expected to improve the ohmic contact between metal and InP since it has lower barrier height than InP. However, InGaAs can reduce the optical properties of nano-resonator solar cell since InGaAs can absorb the light. Therefore, the study of the contact resistance between metal and semiconductor and the influence of p-type InGaAs layer inserted between p-type InP and metal layer are performed in this work. The fabrication involves UV lithography and wet chemical etching. On the other hand, the characterization is conducted through transmission line measurement and micro-diode measurement. In this work, it is found that the InGaAs has an influence to reduce the series resistance of solar cell. As an ultimate goal in this work, the fabrication of nano solar cell integrated within optical nano resonator is performed. It involves the design of the mask for electron beam lithography, anodic bonding technique, electronic beam lithography, and dry etching. The results are observed through scanning electron microscopy. In this work, the geometry of nano-resonator solar cell has been developed successfully with a period of 400 nm.
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