Organic photovoltaic device produced from an electrochemical method for depositing nanofibrilar poly(3,4-ethylenedioxythiophene) (pedot) hole extraction layer in organic solar cells

Abstract

An electrochemical method for producing a hole extraction layer in a solar cell based on organic semiconductor materials. Conjugated polymers are used to build a hole extraction layer and a photoactive layer. Poly(3,4-ethylenedioxythiophene) (PEDOT) is used as a hole extraction layer and is deposited electrochemically from an aqueous solution on an indium tin oxide (ITO) electrode. A nanofibrilar or nanogranular morphology of the PEDOT is achieved by carrying out the polymerization in the presence of a surfactant. A photoactive layer of poly(3-hexylthiophene)/[6,6]-phenyl-C 61 -butyric acid methyl ester (P3HT/PCBM) can be deposited by spin-coating technique on top of the PEDOT layer.

What is claimed is: 
     
         1 . An organic photovoltaic device (OPVd) produced using a PEDOT layer deposited electrochemically on an ITO electrode, comprising:
 a) a transparent conductive ITO layer on a substrate;   b) a nanofibrilar or nanogranular layer of PEDOT deposited electrochemically on the ITO layer;   c) a photoactive layer of poly(3-hexylthiophene)/[6,6]-phenyl-C 61 -butyric acid methyl ester (P3HT/PCBM) deposited by spin-coating technique on top of the PEDOT layer; and   d) an aluminum layer deposited on top of the photoactive layer.   
     
     
         2 . The organic photovoltaic device according to  claim 1 , further comprising electrical contacts connected to the ITO layer and to the aluminum layer. 
     
     
         3 . The organic photovoltaic device according to  claim 1 , wherein the substrate is a transparent glass or flexible polymer film. 
     
     
         4 . The organic photovoltaic device according to  claim 1 , wherein the aluminum layer is deposited by thermal vacuum deposition, e-beam deposition, or sputtering method. 
     
     
         5 . The organic photovoltaic device according to  claim 1 , wherein the ITO layer is a coated glass slide. 
     
     
         6 . The organic photovoltaic device according to  claim 1 , wherein the device is produced by a method comprising the steps of:
 a) cleaning the ITO electrode consecutively with chloroform, isopropanol and deionized water;   b) preparing an aqueous solution of surfactant in 0.5 M NaNO 3  electrolyte;   c) solubilizing 3,4-ethylenedioxythiophene (EDOT) in the surfactant/NaNO 3  solution;   d) polymerizing the EDOT from the prepared solution on the surface of the ITO coated glass slide by applying anodic oxidative current; and   e) washing the deposited PEDOT layer with deionized water and drying the PEDOT layer at 60° C.   
     
     
         7 . The organic photovoltaic device according to  claim 6 , wherein the surfactant is anionic, cationic, zwitterionic, or nonionic. 
     
     
         8 . The organic photovoltaic device according to  claim 7 , wherein the surfactant forms cylindrical micelles, interconnected worm-like micelles or bilayers and the polymerized PEDOT layer has a nanofibrilar morphology. 
     
     
         9 . The organic photovoltaic device according to  claim 7 , wherein the surfactant forms spherical micelles and the polymerized PEDOT layer has a granular morphology. 
     
     
         10 . The organic photovoltaic device according to  claim 7 , wherein the surfactant forms micelles, and further comprising effecting the shape and the size of the surfactant micelles and hence the morphology of the PEDOT layer by changing the ionic strength of the aqueous solution. 
     
     
         11 . The organic photovoltaic device according to  claim 7 , further comprising adjusting the rate of the EDOT polymerization and hence the morphology of the PEDOT layer by changing the current density passing through the solution. 
     
     
         12 . The organic photovoltaic device according to  claim 7 , further comprising adjusting the rate of the EDOT polymerization and hence the morphology of the PEDOT layer by changing the oxidative potential of the ITO electrode. 
     
     
         13 . The organic photovoltaic device according to  claim 7 , further comprising effecting the size and the shape of the surfactant micelles and hence the morphology of the PEDOT layer by adjusting the concentration of the monomer. 
     
     
         14 . The organic photovoltaic device according to  claim 2 , wherein the ITO electrode is a coated glass slide.