Low-cost Extremely Thinlayer Absorber (ETA) Solar Cell: A Novel approach to make the conformal ETA Layers

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The Extremely Thin Absorber-layer (ETA) solar cell is a relatively new PV configuration. In materials viewpoint, there are a large number of semiconductor materials available that are suitable to employ in ETA cell configuration. Most of them are yet to be tested in ETA cell. The first part of the project will be aimed at screening semiconductor material combinations to find out novel material combinations (high band gap n-type semiconductor/low band gap light absorbing semiconductor/high band gap p-type semiconductor) for ETA cells. This will be done by aligning the band gap and band edges of semiconductors. The next part of the project is the construction of the integrated ALD and CVD deposition system. The main advantage of constructing this deposition system is that it will give us the capability of depositing conformal layers of light absorbing low band gap semiconductor materials on high aspect ratio of microstructures. The system will also be capable of deposition of pin-hole free compact layers and deposition of p-type high band gap semiconductors on high aspect ratio microstructures. Initially, a compact high band gap metal oxide semiconductor thin film will be deposited on FTO substrates using spray pyrolysis (to be used as a blocking layer). For the comparison the integrated deposition system will also be employed to make compact blocking layers. Then a microstructured porous film of the same high band gap semiconductor will be deposited on the compact layer. For this, a suitable deposition method will be selected from a range of methods (i.e. screen printing of sol-gel colloid, doctor-blading of sol-gel colloid, template assisted electrodeposition, spray pyrolysis). Then a conformal layer of light absorbing semiconductor material (i.e. CuInS2, Bi2S3, Cu2S, In2S3) will be deposited by using the integrated ALD and CVD deposition system. A high band gap p-type semiconductor (i.e. CuI, CuCNS, CuAlO2) will be deposited on the conformal layer by a suitable method (i.e. spray pyrolysis, dip coating, electrodeposition, integrated ALD/CVD method, or a combination of these methods). This will follow the deposition of a Au back contact. The completed cells will be characterised by a range of techniques (i.e. photocurrent spectroscopy, steady-state current-voltage plots, intensity modulated photocurrent spectroscopy and charge extraction technique) to study the limiting factors of cells. The resulting information will be fed into cell fabrication in order to improve light harvesting efficiency, photovoltage, and overall conversion efficiency. The project will be carried out by a postdoctoral research assistant who has the necessary skills over a period of three years. He will be supported by a dedicated PhD student (fully-funded by the Faculty of Science, Loughborough University) throughout the project. Regular meetings will be held with our industrial partners (Bac2 Ltd and PolySolar Ltd). The keen interest of industrial partners and their regular input is a key advantage for the project. Based on this work, new ideas, collaborations, and interdisciplinary projects will emerge and further funding will be applied for. In overall, the project will bring new capabilities to UK next generation solar cell research.