Conformal lens over spherical diodes in a pv panel

Abstract

A PV panel is manufactured using a monolayer of small silicon sphere diodes (10-300 microns in diameter) connected in parallel. The spheres are embedded in an uncured aluminum-containing layer on an aluminum foil substrate in a roll-to-roll process, and the aluminum-containing layer is heated to anneal the aluminum-containing layer as well as p-dope the bottom surface of the spheres. The diffusion of the p-type dopants also creates a back surface field in the spheres to improve efficiency. A dielectric layer is formed, and a phosphorus-containing layer is deposited over the spheres to dope the top surface n-type, forming a pn junction. The phosphorus layer is then removed. A conductor is deposited to contact the top surface. Conformal, index-graded lenses are then formed over each of the spheres to form a thin and flexible PV panel.

What is claimed is: 
     
         1 . A process for forming a solar cell structure comprising:
 providing a plurality of diodes on a substrate adapted to convert sunlight to electricity, the diodes having a rounded top surface portion of a first conductivity type for being exposed to the sun and having a bottom surface portion of a second conductivity type;   providing a first conductor electrically contacting the bottom surface portion;   depositing a second conductor electrically contacting the top surface portion; and   depositing a lens material over the top surface portion, wherein, only after the lens material is deposited, a bottom surface of the lens material substantially conforms to the rounded shape of the top surface portion.   
     
     
         2 . The process of  claim 1  wherein the step of depositing the lens material comprises:
 depositing a liquid lens material over the diodes, wherein the liquid lens material substantially conforms to the top surface portion of the diodes by at least surface tension; and 
 curing the liquid lens material to form a first lens. 
 
     
     
         3 . The process of  claim 2  wherein the diodes have an average diameter less than 300 microns, wherein the first conductor comprises a metal layer, and wherein the second conductor comprises a transparent conductor layer, the process further comprising:
 depositing a dielectric layer over the metal layer, the dielectric layer extending between the diodes; and 
 depositing the transparent conductor layer over the dielectric layer to electrically contact the top surface portion of the diodes and electrically interconnect the diodes, 
 wherein the step of depositing the liquid lens material comprises depositing the liquid lens material over the dielectric layer between the diodes and over the transparent conductor layer between the diodes as well as over the top surface portion of the diodes. 
 
     
     
         4 . The process of  claim 3  further comprising depositing a quantum dot layer over the dielectric layer, over the transparent conductor layer, and over the diodes prior to depositing the liquid lens material. 
     
     
         5 . The process of  claim 2  wherein the liquid lens material is deposited by one of coating or printing. 
     
     
         6 . The process of  claim 2  wherein the liquid lens material is deposited over the plurality of diodes and between the diodes without masking the diodes. 
     
     
         7 . The process of  claim 2  wherein the first lens has a first index of refraction, the process further comprising:
 depositing a second liquid lens material over the first lens, a bottom surface of the second liquid lens material conforming to a top surface of the first lens; and 
 curing the second liquid material to form a second lens, the second lens having a second index of refraction lower than the first index of refraction. 
 
     
     
         8 . The process of  claim 2  wherein the liquid lens material comprises first particles transparent to visible light and having an average diameter less than 10 microns, where the first particles are in a first liquid binder which, when cured, has a first index of refraction, the first particles having a second index of refraction higher than the first index of refraction. 
     
     
         9 . The process of  claim 8  wherein the first particles have an average diameter less than 300 nm. 
     
     
         10 . The process of  claim 8  further comprising:
 depositing a second liquid lens material over the first lens, a bottom surface of the second liquid lens material conforming to a top surface of the first lens; and 
 curing the second liquid material to form a second lens, the second lens having a third index of refraction lower than the second index of refraction. 
 
     
     
         11 . The process of  claim 10  wherein the second liquid lens material comprises second particles transparent to visible light in a second liquid binder. 
     
     
         12 . The process of  claim 11  wherein the second particles have approximately the third index of refraction, and the second liquid binder, when cured, also has approximately the third index of refraction. 
     
     
         13 . The process of  claim 8  wherein the first particles comprise glass beads. 
     
     
         14 . A solar cell structure comprising:
 a plurality of diodes on a substrate adapted to convert sunlight to electricity, the diodes having a rounded top surface portion of a first conductivity type for being exposed to the sun and having a bottom surface portion of a second conductivity type;   a first conductor electrically contacting the bottom surface portion;   a second conductor electrically contacting the top surface portion; and   a first lens, formed of a first lens material deposited over the top surface portion as a liquid, then cured, such that a bottom surface of the first lens has substantially conformed around the rounded shape of the top surface portion.   
     
     
         15 . The structure of  claim 14  wherein the diodes have a substantially spherical shape, wherein the first lens material substantially conforms to the top surface portion of the diodes by at least surface tension. 
     
     
         16 . The structure of  claim 14  wherein the diodes have an average diameter less than 300 microns, wherein the first conductor comprises a metal layer, and wherein the second conductor comprises a transparent conductor layer, the panel further comprising:
 a dielectric layer over the metal layer, the dielectric layer extending between the diodes; and 
 the transparent conductor layer being over the dielectric layer to electrically contact the top surface portion of the diodes and electrically interconnect the diodes, 
 wherein the first lens material overlies the dielectric layer between the diodes and over the transparent conductor layer between the diodes as well as over the top surface portion of the diodes. 
 
     
     
         17 . The structure of  claim 16  further comprising a quantum dot layer over the dielectric layer, over the transparent conductor layer, and over the diodes, the first lens being formed over the quantum dot layer. 
     
     
         18 . The structure of  claim 14  wherein the first lens has a first index of refraction, the panel further comprising:
 a second lens formed over the first lens, the second lens formed of a second lens material deposited over the first lens, then cured, a bottom surface of the second lens conforming to a top surface of the first lens, the second lens having a second index of refraction lower than the first index of refraction. 
 
     
     
         19 . The structure of  claim 14  wherein the first lens comprises first particles transparent to visible light, the first particles having an average diameter less than 10 microns, where the first transparent particles are in a first binder having a first index of refraction, the first transparent particles having a second index of refraction higher than the first index of refraction. 
     
     
         20 . The structure of  claim 19  wherein the first particles have an average diameter less than 300 nm. 
     
     
         21 . The structure of  claim 19  further comprising:
 a second lens formed over the first lens, the second lens formed of a second lens material deposited over the first lens, then cured, a bottom surface of the second lens conforming to a top surface of the first lens, the second lens having a third index of refraction lower than the second index of refraction. 
 
     
     
         22 . The structure of  claim 21  wherein the second lens comprises second particles transparent to visible light in a second binder, wherein the second particles have approximately the third index of refraction, and the second binder also has approximately the third index of refraction.