Atomic layer deposition for photovoltaic devices

Abstract

A photovoltaic device and method include a substrate, a conductive layer formed on the substrate and an absorber layer formed on the conductive layer from a Cu—Zn—Sn containing chalcogenide material. An emitter layer is formed on the absorber layer and a buffer layer is formed on the emitter layer including an atomic layer deposition (ALD) layer. A transparent conductor layer is formed on the buffer layer.

1 . A method for forming a photovoltaic device, comprising:
 depositing a conductive layer on a substrate;   forming an absorber layer formed from a Cu—Zn—Sn containing chalcogenide material on the conductive layer;   forming a cadmium including emitter layer on the absorber layer;   depositing a buffer layer on the emitter layer by employing an atomic layer deposition (ALD) process to form the buffer layer; and   depositing a transparent conductor layer formed on the buffer layer.   
     
     
         2 . The method as recited in  claim 1 , wherein the Cu—Zn—Sn containing chalcogenide material is a compound with a kesterite structure of the formula: Cu 2−x Zn 1+y Sn(S 1−z Se z ) 4+q  wherein 0≦x≦1; 0≦y≦1; 0≦z≦1; −1≦q≦1. 
     
     
         3 . The method as recited in  claim 1 , wherein the emitter layer includes one of CdS, and CdTe. 
     
     
         4 . The method as recited in  claim 1 , wherein the buffer layer includes Al 2 O 3  and the thickness of the buffer layer is between about 8 and about 25 Angstroms. 
     
     
         5 . The method as recited in  claim 1 , wherein the conductive layer includes molybdenum and the substrate includes a glass substrate. 
     
     
         6 . The method as recited in  claim 1 , further comprising forming a passivation layer in contact with the absorber layer, the passivation layer including an atomic layer deposition (ALD) layer having a thickness of less than about 25 Angstroms. 
     
     
         7 . The method as recited in  claim 6 , wherein the passivation layer includes Al 2 O 3  and the thickness of the passivation layer is between about 8 and about 15 Angstroms. 
     
     
         8 . The method as recited in  claim 6 , wherein the passivation layer is formed between the conductive layer and the absorber layer, the method further comprising: forming a wetting layer on the passivation layer to aid in forming the absorber layer. 
     
     
         9 . The method of  claim 1 , wherein the aluminum oxide including buffer layer includes Al 2 O 3  and the thickness of the buffer layer is between about 5 and about 20 Angstroms. 
     
     
         10 . The method of  claim 9 , wherein efficiency of the photovoltaic device is about 8.5%.