Research On Polymer Solar Cells Based On Metal Electrode

The importance of solar cells has gone beyond people’s expectation after it has been discovered. Its’research has not been limited to the academic field, highly efficient solar cells can grow into an industry that can improve the quality of human beings’survival and affect the future of human beings deeply. Reducing the cost of silicon solar cells is very difficult due to the high cost of silicon.. Compared with silicon solar cells, organic solar cells take advantage of large manufacturing area, low cost, simple, flexible benefits, are a kind of promising cell. Although it owns many advantages, its efficiency is still low, there are some main factors affecting its efficiency including the ability of exciton generation, exciton dissociation, carrier collection and so on.ITO is a commonly used anode material in organic solar cells because of its high transmittance. However, acidic PEDOT would corrode ITO, and resulting in a degradation of the solar cell performance. Our idea is to use metal electrode replacing ITO. Through optimizing the Ag thickness, organic solar cells with comparable performance to that of the ITO-based cells have been obtained.Ag film with various thickness of12nm,14nm,16nm,18nm and30nm has been fabricated by thermal evaporation. Transmission, conductive properties and surface roughness of the Ag films has been measured, which indicates that transmittance decreases as thickness increases, while conductivity becomes better with the increasing of the thickness. Film surface roughness increases as the thickness increased. Solar cell with the structure of Ag/PEDOT:PSS (35nm)/P3HT:PCBM (120nm)/Ca (3nm)/Ag (80nm) was fabricated. The efficiency of solar cell is about3.6%, when the thickness of the Ag anode is16nm.Surface-plasmon enhanced absorption of solar cells has been studied. Grating with different period has been directly fabricated onto the functional layer of the solar cell by laser ablation. Four devices with different structure of Glass/Ag (50nm) n Glass/P3HT:PCBM(90nm)^Glass/P3HT:PCBM (90nm)/Ag (50nm) Glass/P3HT:PCBM with Grating/Ag (50nm) were fabricated and absorption measurements were performed. The device containing the grating structure shows enhanced absorption and exhibits an absorption peak corresponding to surface plasmon resonance. The absorption spectra of devices with different periodic of grating were compared, which indicates that as the grating period decreases, a blueshift of the plasmon resonance can be observed. These results demonstrated that through the introduction of the grating with appropriate period into the organic solar cell, enhanced efficiency can be expected by the surface plasmon enhanced absorption.