The Treatment And Doping Of PEDOT:PSS And Its Application In Organic Solar Cells

Photovoltaic technology has been considered as one of the most efficient approaches to energy demand and environmental protection.Organic solar cells have been attracting great attention due to their advantage of easy fabrication,light weight,and excellent mechanical flexibility.Most of organic solar cells reported in the literature are fabricated on indium tin oxide(ITO)glass substrates and using vacuum-deposited metals used as the top electrodes.However,the problems that ITO possesses high mechanically brittleness and high price limit its application in optoelectronic devices.Simultaneously,the vacuum deposition of top metal electrodes is high energy-consuming and requires expensive deposition facilities.So,it has become important for organic solar cell to develop novel low-price and flexible electrode.In this dissertation,we focused on the research of transparent conductive polymer PEDOT:PSS.The conductivity of the PEDOT:PSS films were enhanced and the work function of PEDOT:PSS was decreased by dipping method or post treatment,and the films were used to fabricated solar cells as top electrode or bottom electrode.Specific work as follows:1.We report a nonionic surfactant(polyethylene glycol 2,5,8,11-tetramethyl-6-dodecyne-5,8-diolether,PEG-TmDD)that can improve the wetting property of PEDOT:PSS aqueous solution on the organic photoactive layer and simultaneously enhance the electrical conductivity of PEDOT:PSS film up to 526 S/cm.Furthermore,the conductivity enhancement is significantly dependent on the thermal annealing,which is different from the conductivity behavior of PEDOT:PSS film prepared from the formulation added with ethylene glycol(EG)where the conductivity is almost independent of the thermal annealing.The temperature dependence of the conductivity of PEDOT:PSS by PEG-TmDD is possibly ascribed to decomposition of PEG-TmDD into EG and TmDD during thermal annealing.With the high conductivity and good wetting on the active layer,PEDOT:PSS mixed with PEG-TmDD is used as the top electrode for organic solar cells.The cells exhibit a fill factor of 60% and a power conversion efficiency of 4.1% using poly(3-hexylthiophene):indene-C60 bis-adduct as the active layer.The results indicate that the new formulation of PEDOT:PSS mixed with PEG-TmDD is suitable for preparing a top electrode for vacuum-free organic solar cells.2.We report the conductivity of poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate)(PEDOT:PSS)can be enhanced to 1460 S/cm via phosphoric acid(H3PO4)treatment.The conductivity enhancement is associated with the partial removal of PSS from the film.The H3PO4 treatment is compatible with plastic substrates,while sulfuric acid(H2SO4)can easily damage the plastic substrate.The PEDOT:PSS film with low work function can be fabricated by spin coated a thin layer of PEI on the surface of the film.With the PEDOT:PSS films as the top and bottom electrode,we have demonstrated ITO-free,metal-free and flexible all-plastic solar cells(PES/ PEDOT:PSS/PEI/P3HT:ICBA/PEDOT:PSS).The cells exhibit a VOC of 0.84 V and a high FF of 60%.The cells have the advantage of light weight and excellent flexibility.The device could help power the coming wave of flexible electronics.