Effects Of Doped PEDOT:PSS On Performance Of Polymer Solar Cells

Polymer solar cell is a new kind of solar cells, which has been one of the researchfocus in solar cell field at present as its many advantages. However, polymer solar cell hasmany disadvantages, such as low power conversion efficiecy (PCE) and poor stability,those disadvantages make polymer solar cells be not commercialized as traditionalinorganic solar cells.The conducting poly (3,4ethylenedioxy-thiophene):poly(styrene sulfonate)(PEDOT:PSS) has been widely used as an interfacial layer or a polymer electrode inpolymer solar cells. PEDOT:PSS layer has many advantages such as high transmission,excellent stability and flexibility. Using dopants is one of the key methods to optimize thequality of PEDOT:PSS because of the improvement of conductivity. This thesis is focusedon the study of doped PEDOT:PSS films and the films as anode buffer layer of polymersolar cells.The main purpose of this research is to improve the performance of polymer solarcells by doping to optimize the PEDOT:PSS films. The work is mainly divided into twoparts, including the study of various doped PEDOT:PSS films, and the study of the relatedpolymer solar cells. Here, acetonitrile as a dopant of PEDOT:PSS has never been reportedbefore.In this thesis, the optical properties, electrical properties and surface roughness of thePEDOT:PSS films, which were treated with different volume fraction of DMSO orglycerol or acetonitrile, were studied, respectively. In order to find out the mechanism ofoptimization of the doped PEDOT:PSS films, the fourier transform infrared(FT-IR)spectrometer was used to measure the infrared spectrum of doped PEDOT:PSS. Then,polymer solar cells with doped PEDOT:PSS films as anode buffer layer were investigated.In this experiment, the structure of polymer solar cells isITO/PEDOT:PSS/P3HT:PCBM/Ca/Al. This thesis also introduces the preparation of dopedPEDOT:PSS blend solution in detail and the preparation of the polymer solar cells.Experimental results show that the transmittance of doped-PEDOT:PSS films isslightly increased and the electrical conductivity of doped-PEDOT:PSS films issignificantly increased. According to the Fourier Transform infrared spectra ofPEDOT:PSS, DMSO-doped PEDOT:PSS, glycerol-doped PEDOT:PSS andacetonitrile-doped PEDOT:PSS, it can be found that DMSO or acetonitrile doesn’t changethe molecular structure of PEDOT:PSS, while glycerol does. Thus, the mechanism of theincreasing in the conductivity of DMSO or acetonitrile-doped PEDOT:PSS films is notrelated to conformational changes.In the experiments of DMSO doped-PEDOT:PSS,0%,3%,5%,10%,15%,20%DMSO were doped into PEDOT:PSS and the spin-coated PEDOT:PSS films and deviceswere studied. The results show that the conductivity of the undoped PEDOT:PSS films is0.28S/cm, the PCE of the corresponding device is0.66%; the conductivity of3%DMSO-doped PEDOT:PSS films was the highest, namely41.52S/cm, the PCE of the corresponding device is3.79%, Jscis18.31mA/cm2，Vocis0.53V，FF is39.1%, which arethe best results.In this paper,0%,3%,5%,10%,15%,20%glycerol and acetonitrile-doped PEDOT:PSS films and the polymer solar cells were also study. For these two dopants, theconductivity of doped PEDOT:PSS films is significantly increased, and then, decreasedwith the volume. The conductivity of the3%glycerol-doped PEDOT:PSS and the3%acetonitrile-doped PEDOT:PSS is also increased obviously. The highest PCE values of2.70%and1.27%are obtained by useing3%glycerol-doped PEDOT:PSS and3%acetonitrile-doped PEDOT:PSS as anode buffer layers, respectively.Consequently, the highest PCE values of the devices fabricated by the three dopantstreated PEDOT:PSS reach at3%, respectively. The device of3%DMSO-dopedPEDOT:PSS prepared device is the best one.