Hybrid window layer for photovoltaic cells

Abstract

A novel photovoltaic solar cell and method of making the same are disclosed. The solar cell includes: at least one absorber layer which could either be a lightly doped layer or an undoped layer, and at least a doped window-layers which comprise at least two sub-window-layers. The first sub-window-layer, which is next to the absorber-layer, is deposited to form desirable junction with the absorber-layer. The second sub-window-layer, which is next to the first sub-window-layer, but not in direct contact with the absorber-layer, is deposited in order to have transmission higher than the first-sub-window-layer.

1 - 94 . (canceled) 
     
     
         95 . A method for manufacturing a solar cell comprising the steps of:
 (i) providing a transparent substrate;   (ii) depositing a transparent conducting oxide layer on the transparent substrate;   (iii) depositing a second nano-crystalline silicon sub-p-layer on the transparent conducting oxide layer substrate at a second temperature;   (iv) depositing a first nano-crystalline silicon sub-p-layer on the second sub-p-layer at a first temperature that is different from the second temperature;   (v) depositing an i-layer on the first nano-crystalline silicon sub-p-layer; and   (vi) depositing an n-type semi-conductor layer on the i-layer substrate.   
     
     
         96 . The method of  claim 95 , wherein during the i-layer deposition, a GeH 4  to Si 2 H 6  ratio provides a Ge content sufficient to forming a high efficiency single-junction solar cell. 
     
     
         97 . The method of  claim 95 , wherein a ratio of hydrogen dilution to a deposition gas of about 5-100 is used to form the i-layer. 
     
     
         98 . The method of  claim 95 , wherein the transparent substrate comprises glass or plastic. 
     
     
         99 . The method of  claim 95 , wherein the first and second nano-crystalline silicon sub-p-layers are deposited by a chemical vapor deposition process. 
     
     
         100 . The method of  claim 99 , wherein the chemical vapor deposition process comprises a plasma enhanced chemical vapor deposition process. 
     
     
         101 . The method of  claim 100 , in which the plasma enhanced chemical vapor deposition comprises a radio frequency plasma enhanced chemical vapor deposition process. 
     
     
         102 . The method of  claim 95 , wherein the i-layer comprises hydrogenated amorphous silicon germanium having a bandgap ranging from about 1.4 e-V to about 1.6 e-V, and wherein the first and second nano-crystalline sub-p-layers have a bandgap of around 1.6 e-V. 
     
     
         103 . The method of  claim 100 , wherein the plasma enhanced chemical vapor deposition includes at least one of the following: cathodic direct current glow discharge, anodic direct current glow discharge, radio frequency glow discharge, very high frequency (VHF) glow discharge, alternate current glow discharge, or microwave glow discharge at a pressure ranging from about 0.5 to about 5 TORR with a dilution ratio of diluent to feedstock (deposition gas) ranging from about 5:1 to about 200:1. 
     
     
         104 . The method of  claim 95 , wherein the second temperature at which the second nano-crystalline silicon sub-p-layer is deposited is lower than the first temperature at which the first nano-crystalline silicon sub-p-layer is deposited. 
     
     
         105 . The method of  claim 95 , wherein a junction formed between the first nano-crystalline silicon sub-p-layer and the i-layer has a current-voltage relationship where the rate of change of the current-voltage relationship is one of at least a constant or an increasing rate of change. 
     
     
         106 . The method of  claim 95 , wherein the i-layer comprises at least one of amorphous silicon germanium (a-Si (1−x )Ge x ) and hydrogenated amorphous silicon germanium (a-Si (1−x) Ge x :H). 
     
     
         107 . A method for manufacturing a solar cell comprising the steps of:
 (i) providing a transparent substrate;   (ii) depositing a transparent conducting oxide layer on the transparent substrate;   (iii) depositing a second nano-crystalline silicon sub-p-layer on the transparent conducting oxide layer at a second temperature;   (iv) depositing a first nano-crystalline silicon sub-p-layer on the second nano-crystalline silicon sub-p-layer at a first temperature that is different from the second temperature, wherein the second nano-crystalline silicon sub-p-layer is formed from the same material as the first sub-p-layer;   (v) depositing an i-layer on the first sub-p-layer; and   (vi) depositing an n-type layer on the i-layer.   
     
     
         108 . The method of  claim 107 , wherein the second nano-crystalline silicon sub-p-layer has a transparency greater than the first nano-crystalline silicon sub-p-layer. 
     
     
         109 . The method of  claim 107 , wherein there is a minimal mismatch between the bandgap of the first nano-crystalline silicon sub-p-layer and the bandgap of the i-layer. 
     
     
         110 . The method of  claim 107 , wherein the first nano-crystalline silicon sub-p-layer has a first thickness and the second nano-crystalline silicon sub-p-layer has a second thickness that is different from the first thickness. 
     
     
         111 . The method of  claim 110 , wherein the first thickness is in the range of about 0.001 microns to about 0.004 microns, and the second thickness is in the range of about 0.005 microns to about 0.02 microns. 
     
     
         112 . A method for manufacturing a solar cell comprising:
 (i) providing a transparent substrate;   (ii) depositing a transparent conducting oxide layer on the transparent substrate;   (iii) depositing a second sub-p-layer comprised of nano-crystalline silicon on the transparent conducting oxide layer at a second temperature, the second sub-p-layer being doped with a boron-containing compound;   (iv) depositing a first sub-p-layer comprised of nano-crystalline silicon on the second sub-p-layer at a first temperature that is different from the second temperature, the first sub-p-layer being doped with a boron-containing compound;   (v) depositing an i-layer on the first sub-p-layer; and   (vi) depositing an n-type layer on the i-layer.   
     
     
         113 . The method of  claim 112 , wherein the second temperature at which the second nano-crystalline silicon sub-p-layer is deposited is lower than the first temperature at which the first nano-crystalline silicon sub-p-layer is deposited. 
     
     
         114 . The method of  claim 112 , wherein the second nano-crystalline silicon sub-p-layer has a transparency greater than the first nano-crystalline silicon sub-p-layer. 
     
     
         115 . The method of  claim 112 , wherein there is a minimal mismatch between the bandgap of the first nano-crystalline silicon sub-p-layer and the bandgap of the i-layer. 
     
     
         116 . The method of  claim 112 , wherein the first nano-crystalline silicon sub-p-layer has a first thickness and the second nano-crystalline silicon sub-p-layer has a second thickness that is different from the first thickness. 
     
     
         117 . The method of  claim 116 , wherein the first thickness is in the range of about 0.001 microns to about 0.004 microns, and the second thickness is in the range of about 0.005 microns to about 0.02 microns. 
     
     
         118 . The method of  claim 112 , wherein a junction formed between the first nano-crystalline silicon sub-p-layer and the i-layer has a current-voltage relationship where the rate of change of the current-voltage relationship is one of at least a constant or an increasing rate of change.