Research On The Modification Of PEDOT:PSS For Organic/Silicon Heterojunction Solar Cells

Solar cells has received extensive attention all over the world as an important choice to solve energy and environmental problems.The PEDOT:PSS/Si heterojunction solar cell has many unique properties of Silicon（Si）,simple device structure,advantages of economic processing and high theoretical photon-to-electron conversion efficiency（PCE）.The key for fabricating PEDOT:PSS/Si solar cells is the material properties of the PEDOT:PSS layer,which governs key steps in light harvesting,charge carrier separation and extraction,and carrier transport.Although numerous works have confirmed modifying the PEDOT:PSS film capable of enhancing the efficiency for PEDOT:PSS/Si heterojunction solar cells,it is not clear what the dominant origin for the improvement of conductivity of PEDPT:PSS film.The working mechanism of the heterojunction and the relationship between the material properties of the PEDOT:PSS layer and the device performances are poorly understood,Therefore,fundamental understanding of the working mechanism of the heterojunction and the relationship between the material properties of the PEDOT:PSS layer is the key to further improve the efficiency and stability of PEDOT:PSS/Si heterojunction solar cells.In the present thesis,a lot of PEDOT:PSS/Si heterojunction solar cells are fabricated,and the mechanisms of PEDOT:PSS film modification and the heterojunction formation are studied.The detailed research content is as follows:（1）The highly conductive and wettable PEDOT:PSS films were fabricated by combing solvent treatment and additive doping.Specifically,the carrier concentration of the PEDOT:PSS films is found to be boosted from 10¹⁸to 10²¹ cm^-3,this is the major factor for improvement of film conductivity.Such a huge change in carrier concentration not only leads to formation of an inversion layer near the surface of Si absorbers but also extend the width of the built-in electric fields in Si absorbers.（2）The PEDOT:PSS/Si heterojunction solar cells with extremely high V_OCare fabricated,and the correlations between the HOMO of PEDOT:PSS film and the formation of the heterojunction are revealed.The PG modified-PEDOT:PSS solar cell present the largest V_OC,reached to 0.659V.（3）Based on PEDOT:PSS/Si heterojunction solar cells,here we report that color rendering can be made by controlling the thickness and modifying the optical refractive index of the PEDOT:PSS films.The key to achieving the desired refractive index of the PEDOT:PSS layer for a specific color is to select proper doping material.Guided by theoretical modeling analysis,we have developed 1x1cm² silicon heterojunction solar cells with colors across the entire visible spectrum while simultaneously achieving a competitive PCE of 13.2%.