Transparent Conducting Oxide As Top-Electrode In Perovskite Solar Cell By Non-Sputtering Process

Abstract

Techniques for forming a transparent conducting oxide (TCO) top contact using a low temperature process are provided. In one aspect of the invention, a method of forming a TCO on a substrate is provided. The method includes the steps of: generating a source gas of the TCO using e-beam evaporation; generating atomic oxygen using RF plasma; and contacting the substrate with the TCO source gas and the atomic oxygen under conditions sufficient to form the TCO on the substrate. A photovoltaic device is also provided which includes a bottom cell; and a perovskite-based top cell on the kesterite-based bottom cell. The perovskite-based top cell includes a top electrode formed from a TCO.

What is claimed is: 
     
         1 . A photovoltaic device, comprising:
 a bottom cell; and   a perovskite-based top cell on the bottom cell,   wherein the perovskite-based top cell comprises a top electrode formed from a transparent conducting oxide (TCO).   
     
     
         2 . The photovoltaic device of  claim 1 , wherein the TCO is selected from the group consisting of: indium-tin-oxide (ITO), indium-zinc-oxide (IZO), and combinations thereof. 
     
     
         3 . The photovoltaic device of  claim 1 , wherein the bottom cell comprises:
 a substrate;   a kesterite absorber on the substrate;   a buffer layer on the kesterite absorber; and   a transparent contact on the buffer layer.   
     
     
         4 . The photovoltaic device of  claim 3 , wherein the kesterite absorber comprises copper, zinc, tin and one or more of sulfur and selenium. 
     
     
         5 . The photovoltaic device of  claim 3 , wherein the perovskite-based top cell comprises:
 a hole transporting layer on the transparent contact;   a perovskite absorber on the hole transporting layer;   an electron transporting layer on the perovskite absorber; and   the top electrode on the electron transporting layer.   
     
     
         6 . The photovoltaic device of  claim 5 , wherein the hole transporting layer comprises a material selected from the group consisting of: poly(3,4-ethylenedioxythiophene) (PEDOT), poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS), and molybdenum trioxide (MoO 3 ). 
     
     
         7 . The photovoltaic device of  claim 5 , wherein the electron transporting layer comprises a material selected from the group consisting of: phenyl-C61-butyric acid methyl ester (PCBM), C60, and bathocuproine (BCP). 
     
     
         8 . The photovoltaic device of  claim 5 , wherein the top electrode comprises:
 a first TCO layer on the electron transporting layer; and   a second TCO layer on the first TCO layer.   
     
     
         9 . The photovoltaic device of  claim 8 , wherein the first TCO layer and the second TCO layer differ from one another in thickness. 
     
     
         10 . The photovoltaic device of  claim 8 , wherein the first TCO layer and the second TCO layer differ from one another in composition. 
     
     
         11 . The photovoltaic device of  claim 10 , wherein the first TCO layer comprises ITO and the second TCO layer comprises IZO. 
     
     
         12 . The photovoltaic device of  claim 10 , wherein the first TCO layer comprises IZO and the second TCO layer comprises ITO. 
     
     
         13 . The photovoltaic device of  claim 8 , wherein the first TCO layer and the second TCO layer differ from one another in both thickness and composition. 
     
     
         14 . The photovoltaic device of  claim 8 , wherein the first TCO layer has a thickness of from about 10 nanometers to about 20 nanometers, and ranges therebetween. 
     
     
         15 . The photovoltaic device of  claim 8 , wherein the second TCO layer has a thickness of from about 100 nanometers to about 320 nanometers, and ranges therebetween. 
     
     
         16 . The photovoltaic device of  claim 8 , wherein the second TCO layer has an oxygen deficiency of from about 0.5% to about 5%, and ranges therebetween. 
     
     
         17 . A photovoltaic device, comprising:
 a bottom cell comprising:
 a substrate; 
 a kesterite absorber on the substrate; 
 a buffer layer on the kesterite absorber; 
 a transparent contact on the buffer layer; 
   a perovskite-based top cell, on the bottom cell, comprising:
 a hole transporting layer on the transparent contact; 
 a perovskite absorber on the hole transporting layer; 
 an electron transporting layer on the perovskite absorber; and 
 a top electrode on the electron transporting layer, wherein the top electrode comprises: a first TCO layer on the electron transporting layer and a second TCO layer on the first TCO layer, and wherein the first TCO layer and the second TCO layer differ from one another in one or more of thickness and composition. 
   
     
     
         18 . The photovoltaic device of  claim 17 , wherein the first TCO layer comprises ITO and the second TCO layer comprises IZO. 
     
     
         19 . The photovoltaic device of  claim 17 , wherein the first TCO layer comprises IZO and the second TCO layer comprises ITO. 
     
     
         20 . The photovoltaic device of  claim 17 , wherein the first TCO layer has a thickness of from about 10 nanometers to about 20 nanometers, and ranges therebetween, and wherein the second TCO layer has a thickness of from about 100 nanometers to about 320 nanometers, and ranges therebetween.