Solar cell and solar-cell module

Abstract

A solar cell has: an emitter layer formed on a light-receiving-surface side of a crystalline silicon substrate, with a dopant of the opposite conductivity type from the silicon substrate added to the emitter layer, a passivation film formed on the surface of the silicon substrate, an extraction electrode and a collector electrode. The extraction electrode extracts photogenerated charge from the silicon substrate and the collector electrode collects the charge collected at the extraction electrode. The extraction electrode contains a first electrode that consists of a sintered conductive paste. The first electrode, at least, is formed so as to pass through the passivation layer. The collection electrode contains a second electrode that has a higher conductivity than the first electrode. This solar cell reduces contact-resistance losses between the silicon and the electrodes, resistance losses due to electrode resistance, and optical and electrical losses in the emitter layer.

1 . A solar cell comprising a crystalline silicon substrate of one conductivity type having a light-receiving surface, an emitter layer formed on the light-receiving surface side of the substrate and having a dopant of opposite conductivity type added thereto, a passivation film formed on the surface of the substrate, an extraction electrode for extracting photogenerated charge from the silicon substrate, and a collector electrode in contact with at least a portion of the extraction electrode for collecting the charge drawn in the extraction electrode, characterized in that
 the extraction electrode includes a first electrode in the form of a sintered conductive paste containing a dopant for imparting conductivity to silicon, at least the first electrode is formed so as to penetrate through the passivation layer, and the collector electrode includes a second electrode having a higher conductivity than the first electrode.   
     
     
         2 . The solar cell of  claim 1  wherein below the interface between the emitter layer of the silicon substrate and the first electrode, a self-doped region is formed as a result of the dopant in the first electrode being diffused during the sintering step. 
     
     
         3 . The solar cell of  claim 1  wherein the self-doped region has a lower resistivity than the emitter layer disposed adjacent thereto. 
     
     
         4 . The solar cell of  claim 1  wherein the first electrode is formed of a conductive paste based on Ag and containing B, Al, Ga, P, As, In or Sb alone or a compound thereof or a combination thereof as the dopant. 
     
     
         5 . The solar cell of  claim 1  wherein the first electrode is partially contacted or entirely overlaid with the second electrode. 
     
     
         6 . The solar cell of  claim 1  wherein the extraction electrode has a laminate structure consisting of the first and second electrodes, and the collector electrode has a monolayer structure consisting of the second electrode. 
     
     
         7 . The solar cell of  claim 1  wherein the extraction electrode and the collector electrode each have a laminate structure consisting of the first and second electrodes. 
     
     
         8 . The solar cell of  claim 1  wherein the extraction electrode consists of the first electrode, and the collector electrode consists of the second electrode. 
     
     
         9 . The solar cell of  claim 1  wherein the passivation film comprises silicon oxide, silicon nitride, silicon carbide, aluminum oxide, amorphous silicon, microcrystalline silicon or titanium oxide or a combination thereof. 
     
     
         10 . A solar cell comprising a crystalline silicon substrate having a non-light-receiving surface, a passivation film formed on the non-light-receiving surface of the substrate, an extraction electrode for extracting photogenerated charge from the silicon substrate, and a collector electrode disposed at least partially in contact with the extraction electrode for collecting the charge collected in the extraction electrode, characterized in that
 the extraction electrode includes a first electrode in the form of a sintered conductive paste containing a dopant for imparting conductivity to silicon, at least the first electrode is formed so as to penetrate through the passivation layer, and the collector electrode includes a second electrode having a higher conductivity than the first electrode.   
     
     
         11 . The solar cell of  claim 10  wherein at the interface between the silicon substrate and the first electrode, a self-doped region is formed as a result of the dopant in the first electrode being diffused during the sintering step. 
     
     
         12 . The solar cell of  claim 10  wherein the self-doped region has a lower resistivity than a non-self-doped region disposed adjacent thereto. 
     
     
         13 . The solar cell of  claim 10  wherein the first electrode is formed of a conductive paste based on Ag and containing B, Al, Ga, P, As, In or Sb alone or a compound thereof or a combination thereof. 
     
     
         14 . The solar cell of any  claim 10  wherein the first electrode is partially contacted or entirely overlaid with the second electrode. 
     
     
         15 . The solar cell of  claim 10  wherein the extraction electrode has a laminate structure consisting of the first and second electrodes, and the collector electrode has a monolayer structure consisting of the second electrode. 
     
     
         16 . The solar cell of  claim 10  wherein the extraction electrode and the collector electrode each have a laminate structure consisting of the first and second electrodes. 
     
     
         17 . The solar cell of any  claim 10  wherein the extraction electrode consists of the first electrode, and the collector electrode consists of the second electrode. 
     
     
         18 . The solar cell of  claim 10  wherein the passivation film comprises silicon oxide, silicon nitride, silicon carbide, aluminum oxide, amorphous silicon, microcrystalline silicon or titanium oxide or a combination thereof. 
     
     
         19 . A solar cell module comprising electrically connected solar cells according to  claim 1 .