Solar cell and method for preparing same

Abstract

A solar cell includes a light-absorbing layer, comprising a Cu compound or Cd compound, between two electrodes facing each other, has an impurity material layer, comprising an impurity element to be provided to the Cu compound or Cd compound, formed on any one side or both sides between the two electrodes and the light absorbing layer, and has a doping layer formed on one part of the light absorbing layer by means of the impurity element being diffused on the light absorbing layer.

1 . A solar cell comprising: a light absorbing layer composed of a Cu compound or Cd compound between two electrodes facing each other;
 an impurity material layer formed on any one side or both sides between the two electrodes and the light absorbing layer and including an impurity elements to be provided to the Cu compound or Cd compound; and   a doping layer formed on a portion of the light absorbing layer by means of the impurity elements being diffused into the light absorbing layer.   
     
     
         2 . The solar cell of  claim 1 , wherein a p-n junction or an internal electric field layer is formed in the Cu compound or Cd compound by the doping layer. 
     
     
         3 . The solar cell of  claim 1 , wherein the Cu compound or Cd compound has a binary composition. 
     
     
         4 . The solar cell of  claim 3 , wherein the Cu compound is Cu x O y  (wherein, x and y are any positive numbers) or Cu x S y  (wherein, x and y are any positive numbers), and the Cd compound is Cd x Te y  (wherein, x and y are any positive numbers). 
     
     
         5 . The solar cell of  claim 1 , wherein the impurity material layer is composed of a metal oxide containing any one or more of Ti and Si. 
     
     
         6 . The solar cell of  claim 1 , exhibiting a fluctuation in current as voltage is applied in a light irradiation state. 
     
     
         7 . The solar cell of  claim 6 , wherein the fluctuation in current is a current variation of 20% or more with respect to a voltage variation of within 5%. 
     
     
         8 . The solar cell of  claim 6 , wherein the fluctuation in current can be reduced to as a current variation to be within 10% with respect to a voltage variation of within 10% through polling which intensifies an internal electric field. 
     
     
         9 . The solar cell of  claim 6 , wherein the fluctuation in current can be reduced to as the number of times a fluctuation appears decrease through polling which intensifies the internal electric field. 
     
     
         10 . A method for preparing a solar cell, comprising: forming a first electrode on a substrate; forming a light absorbing layer on the first electrode; and forming a second electrode on the light absorbing layer, wherein the method further comprises forming an impurity material layer including an impurity element on the light absorbing layer adjacent to the first electrode or the second electrode in any one side or both sides thereof, and forming a doping layer by diffusing the impurity element into a portion of the light absorbing layer. 
     
     
         11 . The method of  claim 10 , wherein the impurity material layer is formed through a thin film process, or formed by a method of attaching a film containing an impurity material. 
     
     
         12 . The method of  claim 11 , wherein the method of attaching a film comprises: preparing a solution by dispersing particles of the impurity material in an organic solvent; applying the solution on the light absorbing layer; and forming a particle layer of the impurity material by evaporating the solvent. 
     
     
         13 . The method of  claim 11 , wherein the method of attaching a film comprises: forming a film by impregnating the particles of the impurity material into a solvent of a thermoplastic resin and then curing the impregnated particles; and adhering the film on the light absorbing layer. 
     
     
         14 . The method of  claim 12 , wherein the size of the particles of the impurity material is 10 to 100 nm. 
     
     
         15 . The method of  claim 10 , wherein the impurity material layer is formed by reactive ion sputtering, and when the impurity material layer is formed, a negative voltage is applied in a range of 0 V to −5 V to accelerate the doping of the impurity element contained in impurities into the light absorbing layer. 
     
     
         16 . The method of  claim 15 , wherein the reactive ion sputtering comprises: providing a target having a component of the impurity material and injecting an inert gas and a reactive gas in a vacuum state; and forming an oxide by generating plasma to cause the impurity material emitted by means of an Ar ion colliding with the target to react with oxygen plasma. 
     
     
         17 . The method of  claim 10 , wherein the impurity material layer is composed of a metal oxide, and formed by physical vapor deposition (PVD), chemical vapor deposition (CVD), or atomic layer deposition (ALD). 
     
     
         18 . The method of  claim 17 , wherein a metal oxide layer is formed by atomic layer deposition using a precursor containing Ti. 
     
     
         19 . The method of  claim 17 , wherein the metal oxide layer comprises any one of a Ti oxide, a composite oxide of Cu and Ti, and a composite oxide of Cu and Si. 
     
     
         20 . The method of  claim 13 , wherein the size of the particles of the impurity material is 10 to 100 nm.