Solar cell and process for producing the same

Abstract

The present invention provides a solar cell that is useful for industry and has high photoelectric conversion efficiency and a method of manufacturing the same. A solar cell according to an aspect of the invention includes: a substrate; a buffer layer that is formed on the substrate and is composed of a group-III nitride semiconductor; and a group-III nitride semiconductor layer (p-type layer/an n-type layer) that has a p-n junction therein and is formed on the buffer layer. At least one of the buffer layer and the group-III nitride semiconductor layer having the p-n junction therein has a compound semiconductor layer formed by a sputtering method.

1 . A solar cell comprising:
 a substrate;   a buffer layer that is formed on the substrate and is composed of a group-III nitride semiconductor; and   a group-III nitride semiconductor layers (p-type layer/n-type layer) that have a p-n junction therein and is formed on the buffer layer,   wherein at least one selected from the group consisting of the buffer layer and the group-III nitride semiconductor layers having the p-n junction therein has a compound semiconductor layer formed by a sputtering method.   
     
     
         2 . The solar cell according to  claim 1 ,
 wherein a plurality of the group-III nitride semiconductor layers (p-type layer/n-type layer) having the p-n junction are comprised in a solar cell element.   
     
     
         3 . The solar cell according to  claim 1 ,
 wherein the group-III nitride semiconductor layer is formed of In x Ga (1-x) N (0≦x<1).   
     
     
         4 . The solar cell according to  claim 1 ,
 wherein the substrate is at least one selected from the group consisting of quartz, glass, sapphire, SiC, silicon, zinc oxide, magnesium oxide, manganese oxide, zirconium oxide, manganese zinc iron oxide, magnesium aluminum oxide, zirconium boride, gallium oxide, indium oxide, lithium gallium oxide, lithium aluminum oxide, neodymium gallium oxide, lanthanum strontium aluminum tantalum oxide, strontium titanium oxide and titanium oxide.   
     
     
         5 . The solar cell according to  claim 1 ,
 wherein an n-type electrode and a p-type electrode are formed on at least a portion of or the entire surface of the group-III nitride semiconductor layer.   
     
     
         6 . The solar cell according to  claim 1 ,
 wherein the buffer layer is formed of AlN or GaN.   
     
     
         7 . A method of manufacturing a solar cell, comprising:
 forming a buffer layer comprising a group-III nitride semiconductor on a substrate using a sputtering method; and   forming a group-III nitride semiconductor layer and electrodes on the buffer layer,   wherein the group-III nitride semiconductor layer is formed on the buffer layer by at least one selected from the group consisting of the sputtering method, a MOCVD method, an MBE method, a CBE method, and an MLE method, and the electrodes are formed on the group-III nitride semiconductor layer.   
     
     
         8 . The method of manufacturing a solar cell according to  claim 7 ,
 wherein at least one of group-III nitride semiconductor layers (p-type layer/n-type layer) having a p-n junction therein that are included in the group-III nitride semiconductor layers formed on the buffer layer is formed by the sputtering method.   
     
     
         9 . The method of manufacturing a solar cell according to  claim 7 ,
 wherein the sputtering method comprises reacting nitrogen in a plasma, radical, or atomic state with a group-III element, thereby forming the layer.   
     
     
         10 . The method of manufacturing a solar cell according to  claim 7 , further comprising:
 a first step of alternately repeating a process of supplying only dopant element and a process of simultaneously supplying a compound comprising group-III element and a nitrogen raw material.   
     
     
         11 . The method of manufacturing a solar cell according to  claim 10 , further comprising:
 a second step of performing a heat treatment on the layer formed by the first step.   
     
     
         12 . The method of manufacturing a solar cell according to  claim 11 ,
 wherein a heat treatment temperature is in a range of about 300° C. to about 1200° C.   
     
     
         13 . The method of manufacturing a solar cell according to  claim 11 ,
 wherein the heat treatment is performed in an atmosphere that does not contain a gas of a compound comprising hydrogen atom or hydrogen gas.   
     
     
         14 . The method of manufacturing a solar cell according to  claim 10 ,
 wherein the dopant element is at least one selected from the group consisting of Si, Ge, and Sn.   
     
     
         15 . The method of manufacturing a solar cell according to  claim 10 ,
 wherein the dopant element is at least one of Mg and Zn.