Print Email Facebook Twitter Thin-film silicon triple junction solar cell for solar fuels Title Thin-film silicon triple junction solar cell for solar fuels Author Hamoen, Victor (TU Delft Electrical Engineering, Mathematics and Computer Science) Contributor Perez Rodriguez, P. (mentor) Smets, A.H.M. (graduation committee) Isabella, O. (graduation committee) Ghaffarian Niasar, M. (graduation committee) Degree granting institution Delft University of Technology Programme Electrical Engineering | Sustainable Energy Technology Date 2017-12-21 Abstract The ever increasing installed capacity of renewable, sustainable energy is essential in order to keep the earthhabitable. However, the intermittent nature of solar and wind energy do not strictly follow human energydemands. Therefore an energy of sufficient magnitude buffer is essential to provide a constant supply ofenergy that matches the demand as closely as possible. Chemical energy shows high potential in terms ofclean, long-term energy storage with efficient conversion to electricity.The DEMO project intends on manufacturing a monolithic photovoltaic device for the production of hydrogengas and hydrocarbon products by the electrochemical splitting of water and carbon dioxide. an aSi:H/a-SiGe:H/nc-Si:Htriple junction device is proposed to generate a combination of voltage and currentto drive the electrochemical reactions efficiently, while simultaneously addressing scalability by using earthabundantmaterials.In this thesis, efforts were made to optimise the a-SiGe:H subcell as well as finding the optimal combinationof materials to use as tunnel recombination junctions as intermediate layers between subcells of themulti-junction device.The best performing a-SiGe:H p-i-n single-junction device achieved a VOC = 719 mV, JSC =17.2 mA/cm2,F F = 0.63 and η = 7.85% as processed on an Asahi VU superstrate. This performance was observed show astrong decline with increasing intrinsic layer thickness and increasing deposition rate. Although a conclusiveoptimal device structure was not obtained, it is believed that bandgap profiling by adjusting the germaniumcontent in the intrinsic layer as well as applying buffer layers can substantially improve the performance ofthe a-SiGe:H single-junction solar cell.To assess long-term stability, an a-SiGe:H single-junction device was subdued to 1000h light soaking.Meta-stable defects induced by recombination of photo-generated charge carriers resulted is a strong degradationin F F of 20% relative. VOC and JSC showed similar relative decreases in performance with 9.0% and8.6%, respectively. The resulting relative drop in conversion efficiency for the degraded solar cell is observedto be 34%.The best tunnel recombination junction for an a-Si:H/a-SiGe:H double junction consists of a 5 nm highlydoped n+-type nc-SiOx :H layer with a 2 nm nc-Si:H p-layer, placed between 25 nm nc-SiOx :H n-layer anda 16 nm nc-SiOx :H p-layer that resulted in good combination of F F, VOC and JSC by improved tunnelling,charge separation and better light management.The best tunnel recombination junction for an a-SiGe:H/nc-Si:H double-junction consists of a highlydoped n+ nc-SiOx :H layer with a 2 nm nc-Si:H p-layer. These layers are sandwiched between an 50 nm ncSiOx:H n-layer, of which the first half has linearly increasing oxygen content, and a 16 nm nc-SiOx :H p-layerof the a-SiGe:H subcell and nc-Si:H subcell, respectively.These tunnel recombination junctions were used to further develop a p-i-n a-Si:H/a-SiGe:H/nc-Si:H triplejunctionsolar cell on a wet-etched glass superstrate with ZnO:Al as both sacrificial layer for texturing andas transparent conductive oxide. The best performing triple-junction device achieved a VOC = 1.96 V, JSC =6.21 mA/cm2, F F = 0.63 and η = 7.63% with respective intrinsic layer thicknesses of 175 nm/120 nm/3000 nm.The conversion efficiency of this current mismatched device is throttled by the current limiting a-SiGe:H middlecell. Enhancing the a-SiGe:H material quality allows for thicker absorber layer to increase current generationwithout compromising the electrical performance, which can significantly improve the performance thetriple-junction device.This device is able to achieve an estimated solar-to-fuels efficiency of 4.9% for producing hydrogen witha high performance electrode and an an IrOx counter electrode. Assuming similar electrode performance,the solar-to-fuels efficiency for producing both hydrogen and methane is expected to be 2.4%. Hydrocarbonswith higher electrochemical potential are not likely to be produced with such a device due to the higherelectrochemical potentials.Using the measured degraded performance of the a-SiGe:H subcell, a relative decrease in water splittingefficiency of 21% is expected for the triple-junction device. Subject Triple junctionThin-filmSolar cellSilicon germaniumTunnel recombination junctionTRJSiGeLight-induced degradationLIDStaebler-Wronski effectSWE To reference this document use: http://resolver.tudelft.nl/uuid:2e3290cd-48c3-443d-8f49-1a80c06da7e5 Part of collection Student theses Document type master thesis Rights © 2017 Victor Hamoen Files PDF Master_thesis_Victor_Hamo ... _fuels.pdf 9.1 MB Close viewer /islandora/object/uuid:2e3290cd-48c3-443d-8f49-1a80c06da7e5/datastream/OBJ/view