Solar cells formed via aluminum electroplating

Abstract

Electroplating of aluminum may be utilized to form electrodes for solar cells. In contrast to expensive silver electrodes, aluminum allows for reduced cell cost and addresses the problem of material scarcity. In contrast to copper electrodes which typically require barrier layers, aluminum allows for simplified cell structures and fabrication steps. In the solar cells, point contacts may be utilized in the backside electrodes for increased efficiency. Solar cells formed in accordance with the present disclosure enable large-scale and cost-effective deployment of solar photovoltaic systems.

What is claimed is: 
     
         1 . A method for electroplating of aluminum onto silicon, comprising:
 preparing an ionic liquid comprising aluminum chloride (AlCl 3 ) and an organic halide (RX), the ionic liquid having a molar ratio of AlCl 3 : RX greater than 1;   cleaning a silicon substrate with at least one of hydrogen fluoride, hydrogen chloride, hydrogen peroxide, or ammonia hydroxide;   depositing aluminum onto the silicon substrate via an electroplating process incorporating the ionic liquid;   cleaning the silicon substrate with alcohol and deionized water; and   annealing the silicon substrate to reduce the resistivity of the electroplated aluminum.   
     
     
         2 . The method of  claim 1 , wherein the molar ratio is 3:2. 
     
     
         3 . The method of  claim 1 , wherein the organic halide is 1-ethyl-3-methylimidazolium. 
     
     
         4 . The method of  claim 1 , wherein the deposition of aluminum is performed galvanostatically. 
     
     
         5 . The method of  claim 1 , wherein the electroplating process utilizes a 2-electrode cell. 
     
     
         6 . The method of  claim 1 , wherein the electroplating process utilizes a 3-electrode cell. 
     
     
         7 . The method of  claim 1 , wherein the depositing is performed with the ionic liquid at a temperature of between 100 degrees Celsius and 150 degrees Celsius. 
     
     
         8 . An n-type back-emitter solar cell, comprising:
 a front finger electrode comprising aluminum and formed by electroplating of aluminum onto silicon over a patterned SiNx layer; and   a rear electrode comprising aluminum and formed by at least one of electroplating or screen printing,   wherein an electrical contact between the front finger electrode and the n-type front surface field of the solar cell is formed by firing at a temperature between about 100 degrees Celsius and about 500 degrees Celsius.   
     
     
         9 . The solar cell of  claim 8 , wherein the electroplating of aluminum onto silicon is performed at a temperature of between 100 degrees Celsius and 150 degrees Celsius. 
     
     
         10 . An n-type back-emitter point-back-contact solar cell, comprising:
 a front finger electrode comprising aluminum electroplated over a patterned SiNx layer; and   a rear electrode comprising aluminum over a layer of at least one of SiO 2  or Al 2 O 3 .   
     
     
         11 . The solar cell of  claim 10 , wherein the rear electrode comprises a screen-printed aluminum layer, and wherein point contacts were formed through the SiO 2  or Al 2 O 3  layer via laser annealing. 
     
     
         12 . The solar cell of  claim 10 , wherein the rear electrode comprises a screen-printed aluminum layer, and wherein point contacts were formed in the aluminum layer upon annealing due to patterns in the SiO 2  or Al 2 O 3 . 
     
     
         13 . The solar cell of  claim 10 , wherein the solar cell is configured with efficiency above 15%. 
     
     
         14 . The solar cell of  claim 10 , wherein the front finger electrode was electroplated galvanostatically. 
     
     
         15 . The solar cell of  claim 14 , wherein the front finger electrode was electroplated at a temperature of between 100 degrees Celsius and 150 degrees Celsius.