| The mass production of silicon thin-film solar cells, typically deposited on cost effective ceramic substrates, depends on enhancing the performance and lowering the cost. Among other active layers inside the cell, peformance enhancement depends on a layer that separate the light absorbing layers from the emitter. Ideally this intermediate layer, also known as buffer layer should be deposited with cost effective techniques, be conductive and should feature optical confinement. Furthermore the buffer layer should withstand high temperatures and harsh chemical environments like they occur during solar cell processing. Especially stability against oxidizing solvents like nitric acid (HNO3) or inactivity during e.g., oxide removing steps with hydrofluoric (HF) is required. Semiconducting materials like SiC, InP, InSb, GaAs, etc. have the properties to be used as buffer layer. For example Silicon Carbide (SiC) particularly in crystalline form deposited by atmospheric pressure chemical vapour deposition (APCVD) can match all those requirements and additionally fits the thermal properties of crystalline silicon. Use of such intermediate layers during high temperature steps prevents diffusion of transition metals, originating from the substrates, into active silicon layers. Control doping of these layers results in specific resistivity of less than 100 ohms cm make these layers suitable for use to enhance the performance of advanced electronic devices such as solar cells and thin film transistors (TFTs). The different potentially cost-effective substrates that are used with this type of Si thinfilm solar cell are made from graphite, crystalline silicon, sintered silicon carbide, sintered zircon (ZrSiO4) and glass. . Since the formation of amorphous silicon is unavoidable in the low temperature deposition of microcrystalline silicon on a glass substrate at temperatures less than 550 0C in the plasma-enhanced chemical vapor deposition and hot wire chemical vapor deposition (HWCVD), crystalline silicon films should not be deposited directly on a glass substrate but need to be fabricated by the post treatment of amorphous silicon films, for making thin film solar cell with buffer layer. In this work, beside SiC, buffer layers made of other materials like Indium Phosphide (InP), Indiaum Antimonide (InSb) and Gallium Arsenide (GaAs) were used. Among all of ther buffer layers, solar cell with SiC buffer layes of thickness 5microm showed the best efficiency which is 20.82 %. Solar cell based on InP of thickness 3microm showed an efficiency of 19.60 %. On the other hand solar cell based on InSb of thickness 5microm showed an efficiency of 15.50 %, and based on GaAs of thickness 5microm showed an efficiency of 19.99 %. Among all of the buffer layer materials used in this study SiC appeared to be the best one. |
