Interface Optimization And Performance Improvement Of Silicon/Organic Hybrid Solar Cells

To date, conventional crystalline silicon (c-Si) solar cells play a dominate role in the photovoltaic industry. However, the highly-energy-consuming p-n junction forming process greatly limits the future application of c-Si solar cells. Meanwhile, organic solar cells have been intensively studied due to its merits like easy-to-fabricated and low-cost. The major factor which limits the further development of organic solar cells is its poor spectral response in visible light. Si/organic hybrid solar cells have been increasingly studied as a combination of the good spectral response of Si and the low-temperature synthesis of organics. This paper focuses on the device physics of Si/poly (3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hybrid solar cells. The photovoltaic performance of Si/PEDOT:PSS hybrid solar cells has been improved through the formation of a doping-free selective emitter structure by a tungsten tri-oxide (WO3) thin film, as well as a optimization of back contact by cesium chloride (CsCl). A simpler way to effectively reduce the leakage current has been developed using an edge insulate treatment by PMMA. The main work of this paper includes:1) The fundamental working mechanism of Si/PEDOT:PSS hybrid solar cells has been studied, which is an inversion-layer-based p-n junction solar cell. Meanwhile, an edge insulate treatment has been carried out by Polymethyl Methacrylate (PMMA), which greatly reduces leakage current of the hybrid solar cells. As a result, the fill factor (FF) and open-circuit voltage (Voc) of the hybrid solar cells is largely improved, yielding a power converse efficiency (PCE) of 11.04%.2) A doping-free selective emitter structure is formed by inserting a WO3 interlayer between PEDOT:PSS and silver electrodes, which significantly suppresses the carrier recombination. Besides, the contact resistance between PEDOT:PSS and silver electrodes is also reduced. Therefore, FF and Voc of the hybrid solar cells increases, resulting in better performance.3) Through optimizing back contact of Si/PEDOT:PSS hybrid solar cells by cesium chloride (CsCl), an efficiency as high as 11.81% is obtained, a) Current density versus voltage (J-V) characteristic of the hybrid solar cells in dark circumstance show that carrier recombination of the solar cells is suppressed after the insertion of cesium chloride. A smaller ideal factor (n) indicates better diodes rectification characteristic of the solar cells with cesium chloride, b) The series resistance of solar cells is reduced after the insertion of cesium chloride between aluminum electrode and Si. All above indicate larger FF and Voc of the Si/PEDOT:PSS hybrid solar cells.