Organic thin-film photoelectric conversion element and method of manufacturing the same

Abstract

The objectives of the present invention are to enable the manufacturing of an organic thin-film photoelectric conversion element under normal atmosphere, improve the photoelectric conversion efficiency of the element, and enhance its durability. A hole-blocking TiO2 layer is created between the photoelectric conversion layer and the electrode by a wet process. In the manufacturing process, the hole-blocking TiO2 layer is air-dried so that it will be an amorphous layer. It is possible to provide a concentration gradient layer of PCBM/P3HT in which the PCBM concentration is higher in a region close to the hole-blocking TiO2 layer. This structure will reduce the electric resistance of that region and minimize the current loss within the photoelectric conversion element. In the vicinity of the hole-blocking TiO2 layer, the PCBM concentration is increased, which in turn makes it easier for electrons to flow into the TiO2 layer since PCBM is electrically conductive. Due to these features, the organic thin-film photoelectric conversion element having the gradient structure of the present embodiment has a high level of photoelectric conversion efficiency and good durability.

1 . A method of manufacturing an organic thin-film photoelectric conversion element, wherein a photoelectric conversion layer is created using a solution in which 1 to 30 mg of PCBM as an n-type organic semiconductor component and 0.2 to 20 mg of P3HT as a p-type organic semiconductor component are dissolved in 1 ml of a mixed solvent consisting of 1 to 20% by volume of a poor solvent added to a good solvent, where the poor solvent is one of NMP, benzonitrile and anisole, or a mixture of two or more of them, and the good solvent is chlorobenzene. 
     
     
         2 . The method of manufacturing an organic thin-film photoelectric conversion element according to  claim 1 , wherein:
 the poor solvent is NMP; and   the photoelectric conversion layer is created using the solution in which 1 to 30 mg of PCBM as the n-type organic semiconductor component and 0.2 to 20 mg of P3HT as the p-type organic semiconductor component are dissolved in 1 ml of the mixed solvent consisting of 1.5 to 3% by volume of the poor solvent added to the good solvent.   
     
     
         3 . A method of manufacturing an organic thin-film photoelectric conversion element, comprising:
 preparing a solution by dissolving PCBM as an n-type organic semiconductor component and P3HT as the p-type organic semiconductor component in a mixed solvent containing chlorobenzene as a good solvent and one of NMP, benzonitrile and anisole, or a mixture of two or more of them as a poor solvent; and   applying the solution by spin-coating at a speed of 500 to 10000 rpm to create a photoelectric conversion layer of 20 to 200 nm in thickness.   
     
     
         4 . An organic thin-film photoelectric conversion element, comprising a hole-blocking layer made of amorphous TiO2 produced by wet process without heating between a photoelectric conversion layer and an electrode after the photoelectric conversion layer is created. 
     
     
         5 . The organic thin-film photoelectric conversion element according to  claim 4 , the photoelectric conversion layer has a bulk heterojunction structure consisting of an n-type organic semiconductor and a p-type organic semiconductor and has a concentration gradient along a thickness direction, where the concentration of the n-type organic semiconductor is higher in a region closer to the hole-blocking layer. 
     
     
         6 . The organic thin-film photoelectric conversion element according to  claim 5 , wherein the n-type organic semiconductor component is a fullerene derivative and the p-type organic semiconductor component is a conductive polymer. 
     
     
         7 . The organic thin-film photoelectric conversion element according to  claim 6 , wherein the fullerene derivative is PCBM and the conductive polymer is P3HT. 
     
     
         8 . The method of manufacturing an organic thin-film photoelectric conversion element according to  claim 1 , further comprising an annealing process carried out after the photoelectric conversion layer is created. 
     
     
         9 . The method of manufacturing an organic thin-film photoelectric conversion element according to  claim 3 , further comprising an annealing process carried out after the photoelectric conversion layer is created.