Backside nanoscale texturing to improve IR response of silicon solar cells and photodetectors

Abstract

The absorption coefficient of silicon for infrared light is very low and most solar cells absorb very little of the infrared light energy in sunlight. Very thick cells of crystalline silicon can be used to increase the absorption of infrared light energy but the cost of thick crystalline cells is prohibitive. The present invention relates to the use of less expensive microcrystalline silicon solar cells and the use of backside texturing with diffusive scattering to give a very large increase in the absorption of infrared light. Backside texturing with diffusive scattering and with a smooth front surface of the solar cell results in multiple internal reflections, light trapping, and a large enhancement of the absorption of infrared solar energy.

1 - 20 . (canceled) 
     
     
         21 . A semiconductor solar cell or photodetector having improved incident radiation absorption of visible and infrared light wavelengths, comprising:
 a silicon substrate having a substantially planar first surface available to the incident radiation and a second surface, said second surface being textured to provide diffusive scattering at least of the infrared light wavelengths;   a first layer disposed at said first surface, said first layer being transparent to the visible light and infrared light wavelengths of the incident radiation and internally reflective to the infrared light wavelengths scattered within said silicon substrate;   a second layer disposed at said textured second surface, said second layer having a thickness in a range of 0.1 micrometers to 10 micrometers and being transparent to the visible light and infrared light wavelengths of the incident radiation; and   a reflecting layer disposed at said second layer and spaced apart from said second surface by said second layer, whereby said infrared light wavelengths are returned through said second layer toward said textured second surface of said silicon substrate.   
     
     
         22 . The semiconductor solar cell or photodetector of  claim 21  wherein said second surface is textured to provide Lambertian diffuse scattering. 
     
     
         23 . The semiconductor solar cell or photodetector of  claim 22  wherein said reflective layer returns infrared light wavelengths toward said textured second surface and said textured second surface is textured such that the reflected infrared light wavelengths is Lambertian diffuse scattered in said silicon substrate. 
     
     
         24 . The semiconductor solar cell or photodetector of  claim 21  wherein said first layer is antireflective to visible light of the incident radiation. 
     
     
         25 . The semiconductor solar cell or photodetector of  claim 21  wherein said silicon substrate further comprises single crystalline silicon or multi-crystalline silicon substrate having a thickness in a range of 5 micrometers to 500 micrometers. 
     
     
         26 . The semiconductor solar cell or photodetector of  claim 21  wherein said silicon substrate further comprises deposited microcrystalline silicon having a thickness in a range of 1 micrometer to 10 micrometers. 
     
     
         27 . The semiconductor solar cell or photodetector of  claim 21  wherein said silicon substrate further comprises deposited amorphous silicon having a thickness in a range of 1 micrometer to 10 micrometers. 
     
     
         28 . The semiconductor solar cell or photodetector of  claim 21  wherein said reflecting layer further comprises a metallic layer. 
     
     
         29 . The semiconductor solar cell or photodetector of  claim 21  wherein said reflecting layer further comprises a layer having a thickness in a range of 0.05 micrometers and 5.0 micrometers. 
     
     
         30 . A semiconductor solar cell or photodetector having improved incident radiation absorption of visible and infrared light wavelengths, comprising:
 a silicon substrate having a first surface available to the incident radiation being textured to provide Lambertian diffusive scattering at least of the infrared light wavelengths and having a second surface;   a first layer disposed at said first surface, said first layer being transparent to the visible light and infrared light wavelengths of the incident radiation; and   a reflecting layer disposed adjacent said second surface, whereby said infrared light wavelengths are returned by the reflecting layer toward said textured first surface and into said silicon substrate.   
     
     
         31 . The semiconductor solar cell or photodetector of  claim 30  wherein said first surface further comprises a Lambertian reflective diffuse scattering texture. 
     
     
         32 . The semiconductor solar cell or photodetector of  claim 30  wherein said first layer is antireflective to visible light of the incident radiation. 
     
     
         33 . The semiconductor solar cell or photodetector of  claim 30  wherein said silicon substrate second planar surface returns said infrared light wavelengths from said reflective layer through said substrate. 
     
     
         34 . The semiconductor solar cell or photodetector of  claim 30  wherein said silicon substrate further comprises single crystalline silicon or multi-crystalline silicon substrate having a thickness in a range of 5 micrometers to 500 micrometers. 
     
     
         35 . The semiconductor solar cell or photodetector of  claim 30  wherein said silicon substrate further comprises deposited microcrystalline silicon having a thickness in a range of 1 micrometers to 10 micrometers. 
     
     
         36 . The semiconductor solar cell or photodetector of  claim 30  wherein said silicon substrate further comprises deposited amorphous silicon having a thickness in a range of 1 micrometer to 10 micrometers. 
     
     
         37 . The semiconductor solar cell or photodetector of  claim 30  wherein said reflecting layer further comprises a metallic layer. 
     
     
         38 . The semiconductor solar cell or photodetector of  claim 30  wherein said reflecting layer further comprises a layer having a thickness in a range of 0.05 micrometers and 5.0 micrometers. 
     
     
         39 . A semiconductor solar cell or photodetector having improved incident radiation absorption of visible and infrared light wavelengths, comprising:
 a silicon substrate having a textured first surface available to the incident radiation being textured to provide Lambertian diffusive scattering at least of the infrared light wavelengths and having a second surface;   a first layer disposed at said first surface, said first layer being transparent to the visible light and infrared light wavelengths of the incident radiation;   a second layer disposed at said second surface, said second layer being transparent to the visible light and infrared light wavelengths of the incident radiation; and   a reflecting layer disposed at said second layer and spaced apart from said second surface by said second layer, whereby said infrared light wavelengths are returned through said second layer toward said textured first surface.   
     
     
         40 . The semiconductor solar cell or photodetector of  claim 39  wherein said first surface further comprises a Lambertian reflective diffuse scattering texture. 
     
     
         41 . The semiconductor solar cell or photodetector of  claim 39  wherein said first layer is antireflective to visible light of the incident radiation. 
     
     
         42 . The semiconductor solar cell or photodetector of  claim 39  wherein said silicon substrate second planar surface returns infrared light wavelengths returned from said reflective layer through said substrate. 
     
     
         43 . The semiconductor solar cell or photodetector of  claim 39  wherein said silicon substrate further comprises single crystalline silicon or multi-crystalline silicon substrate having a thickness in a range of 5 micrometers to 500 micrometers. 
     
     
         44 . The semiconductor solar cell or photodetector of  claim 39  wherein said silicon substrate further comprises deposited microcrystalline silicon having a thickness in a range of 1 micrometer to 10 micrometers. 
     
     
         45 . The semiconductor solar cell or photodetector of  claim 39  wherein said silicon substrate further comprises deposited amorphous silicon having a thickness in a range of 1 micrometer to 10 micrometers. 
     
     
         46 . The semiconductor solar cell or photodetector of  claim 39  wherein said reflecting layer further comprises a metallic layer and said second layer further comprises an oxide substantially transparent to infrared wavelengths of radiation. 
     
     
         47 . The semiconductor solar cell or photodetector of  claim 39  wherein said reflecting layer further comprises a layer having a thickness in a range of 0.05 micrometers and 5.0 micrometers. 
     
     
         48 . The semiconductor solar cell or photodetector of  claim 39  wherein said second layer further comprises a layer having a thickness in a range of 0.1 micrometers and 10 micrometers.