Optical properties and conductivity of PEDOT:PSS films treated by polyethylenimine solution for organic solar cells

Abstract We report on conductivity and optical property of three different types of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) films [pristine PH1000 film ( PH1000-p ), with 5 wt.% ethylene glycol additive ( PH1000-EG ) and with sulfuric acid post-treatment ( PH1000-SA )] before and after polyethylenimine (PEI) treatment. The PEI is found to decrease the conductivity of all the PEDOT:PSS films. The processing solvent of 2-methoxyethanol is found to significantly enhance the conductivity of PH1000-p from 1.1 up to 744 S/cm while the processing solvent of isopropanol or water does not change the conductivity of PH1000-p much. As for the optical properties, the PEI treatment slightly changes the transmittance and reflectance of PH1000-p and PH1000-EG films, while the PEI leads to an substantial increase of the absorptance in the spectral region of 400–1100 nm of the PH1000-SA films. Though the optical property and conductivity of the three different types of PEDOT:PSS films vary with the PEI treatment, the treated PEDOT:PSS films exhibit similar low work function. We demonstrate solar cells with a simple device structure of glass/low-WF PEDOT:PSS/P3HT:ICBA/high-WF PEDOT:PSS cells that exhibit good performance with open-circuit voltage of 0.82 V and fill factor up to 0.62 under 100 mW/cm 2 white light illumination.

[1]  Jianyong Ouyang,et al.  "Secondary doping" methods to significantly enhance the conductivity of PEDOT: PSS for its application as transparent electrode of optoelectronic devices , 2013, Displays.

[2]  Zaifang Li,et al.  Polyethylenimine aqueous solution: a low-cost and environmentally friendly formulation to produce low-work-function electrodes for efficient easy-to-fabricate organic solar cells. , 2014, ACS applied materials & interfaces.

[3]  Jong-Hyun Ahn,et al.  Effect of PEDOT Nanofibril Networks on the Conductivity, Flexibility, and Coatability of PEDOT:PSS Films. , 2014, ACS applied materials & interfaces.

[4]  X. Crispin,et al.  Poly(ethylene imine) Impurities Induce n‐doping Reaction in Organic (Semi)Conductors , 2014, Advanced materials.

[5]  Markus Hösel,et al.  Roll-to-roll fabrication of polymer solar cells , 2012 .

[6]  Shangfeng Yang,et al.  High-efficiency ITO-free polymer solar cells using highly conductive PEDOT:PSS/surfactant bilayer transparent anodes , 2013 .

[7]  Yang Yang,et al.  On the mechanism of conductivity enhancement in poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) film through solvent treatment , 2004 .

[8]  Olle Inganäs,et al.  Conductivity of de-doped poly(3,4-ethylenedioxythiophene) , 2002 .

[9]  K. Ho,et al.  Highly conductive PEDOT:PSS electrode by simple film treatment with methanol for ITO-free polymer solar cells , 2012 .

[10]  Bernard Kippelen,et al.  High performance polymeric charge recombination layer for organic tandem solar cells , 2012 .

[11]  Mm Martijn Wienk,et al.  Double and triple junction polymer solar cells processed from solution , 2007 .

[12]  K. Cai,et al.  Enhanced thermoelectric properties of poly(3,4-ethylenedioxythiophene) thin films treated with H2SO4 , 2014 .

[13]  Wenjing Tian,et al.  Investigation on polymer anode design for flexible polymer solar cells , 2008 .

[14]  Bernard Kippelen,et al.  All-plastic solar cells with a high photovoltaic dynamic range , 2014 .

[15]  Ji-hoon Kim,et al.  Thieno[3,2-b]thiophene-Substituted Benzo[1,2-b:4,5-b′]dithiophene as a Promising Building Block for Low Bandgap Semiconducting Polymers for High-Performance Single and Tandem Organic Photovoltaic Cells , 2014 .

[16]  Jianyong Ouyang,et al.  Solution‐Processed Metallic Conducting Polymer Films as Transparent Electrode of Optoelectronic Devices , 2012, Advanced materials.

[17]  Y. Kim,et al.  Highly Conductive PEDOT:PSS Electrode with Optimized Solvent and Thermal Post‐Treatment for ITO‐Free Organic Solar Cells , 2011 .

[18]  N. E. Coates,et al.  Efficient Tandem Polymer Solar Cells Fabricated by All-Solution Processing , 2007, Science.

[19]  Yongfang Li,et al.  Fluorinated Benzoselenadiazole-based Low-Band–Gap Polymers for High Efficiency Inverted Single and Tandem Organic Photovoltaic Cells , 2014 .

[20]  D. Zahn,et al.  Chemical post-treatment and thermoelectric properties of poly(3,4-ethylenedioxylthiophene):poly(styrenesulfonate) thin films , 2014 .

[21]  Jan Obrzut,et al.  Influence of a water rinse on the structure and properties of poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) films. , 2005, Langmuir : the ACS journal of surfaces and colloids.

[22]  Talha M. Khan,et al.  A Universal Method to Produce Low–Work Function Electrodes for Organic Electronics , 2012, Science.

[23]  Yu Xuan,et al.  An all-polymer-air PEDOT battery , 2012 .

[24]  Zaifang Li,et al.  PEDOT:PSS top electrode prepared by transfer lamination using plastic wrap as the transfer medium for organic solar cells , 2014 .

[25]  Bernard Kippelen,et al.  Optimization of a polymer top electrode for inverted semitransparent organic solar cells , 2011 .

[26]  Paolo Lugli,et al.  Efficient indium-tin-oxide (ITO) free top-absorbing organic photodetector with highly transparent polymer top electrode , 2011 .

[27]  Chuan Yi Tang,et al.  A 2.|E|-Bit Distributed Algorithm for the Directed Euler Trail Problem , 1993, Inf. Process. Lett..

[28]  H. J. Yeh,et al.  Blending of poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) with poly(ethyleneimine) as an active layer in depletion-mode organic thin film transistors , 2007 .

[29]  P. Wang,et al.  Highly conductive PEDOT:PSS treated with formic acid for ITO-free polymer solar cells. , 2014, ACS applied materials & interfaces.

[30]  Yang Yang,et al.  A polymer tandem solar cell with 10.6% power conversion efficiency , 2013, Nature Communications.

[31]  Y. H. Kahng,et al.  Transparent Electrodes: Highly Conductive PEDOT:PSS Nanofibrils Induced by Solution‐Processed Crystallization (Adv. Mater. 14/2014) , 2014 .