Interface Property Control In Si/PEDOT:PSS For High Performance Hybrid Solar Cells Via Chemical Bonding

Solar energy, as a green and clean energy source, is one of the effective ways to solve the problems such as energy crisis and environment pollution nowadays, therefore, solar cells have attracted wide interests. Among all kinds solar cells, hybrid organic-inorganic solar cells combine the advantages of organic and inorganic have emerged as a promising candidate for cost-effective photovoltaics. For Si/organic hybrid solar cell, one of the common methods to improve power conversion efficiency (PCE) is to introducing Si nanostructures on substrates, which provide a low reflectivity over a broad range of solar spectrum and enhance light harvesting. However, the light-trapping nanostructures significantly enlarge the surface area of Si substrates and result in additional surface trap states. Moreover, those nanostructured Si substrates provide poor contact with organic layer, all these problems could lead to a high surface recombination velocity and display negative effect on device performance. Aimed at this, this thesis focuses on improving contact between organic layer and nanostructured Si substrates. The work consist the following parts:1.High-density silicon nanowire arrays (SiNWs) were prepared by metal ion-assisted aqueous etching method. The SiNWs were further etched by TMAH (tetramethylammonium hydroxide) solution to tune the surface/volume ratio. By optimizing TMAH treating time, suitable nanostructured Si morphology can be obtained to achieve the best electrical properties.2. The organic-inorganic hybrid solar cells have been fabricated using double-side etching nanostructured Si substrates. By etching the unpolished side of Si to reduce roughness of wafer, the contact between back electrode (Al) and unpolished side has been improved, which is beneficial for electrons collection. The PCE of this kind of device has increased to 12.44%.3. PEDOT:PSS solution with GOPS was applied to organic-inorganic hybrid solar cells to improve PCE of devices. By adjusting the concentrations of GOPS and the spin coating speed, the highest open circuit voltage reached to 640 mV and the PCE of hybrid solar cell was optimized to 14.2%. The improvement of device performance was attributed to better contact between PEDOT:PSS layer and nanostructured Si substrate, which formed a better quality junction of two materials and have good effects to hole transmission and collection.