SOLUTION-BASED FABRICATION OF PHOTOVOLTAIC CELL
An ink for forming CIGS photovoltaic cell active layers is disclosed along with methods for making the ink, methods for making the active layers and a solar cell made with the active layer. The ink contains a mixture of nanoparticles of elements of groups IB, IIIA and (optionally) VIA. The particles are in a desired particle size range of between about 1 nm and about 500 nm in diameter, where a majority of the mass of the particles comprises particles ranging in size from no more than about 40% above or below an average particle size or, if the average particle size is less than about 5 nanometers, from no more than about 2 nanometers above or below the average particle size. The use of such ink avoids the need to expose the material to an H 2 Se gas during the construction of a photovoltaic cell and allows more uniform melting during film annealing, more uniform intermixing of nanoparticles, and allows higher quality absorber films to be formed.
1 . A method for fabricating a liquid containing intermixed elements of groups IB and IIIA, and optionally VIA, comprising the steps of:
forming non-oxide nanoparticles containing elements from group IB; and forming non-oxide nanoparticles containing elements from group IIIA; and optionally forming non-oxide nanoparticles containing elements from group VIA;
combining the non-oxide nanoparticles with a liquid to form an ink;
wherein the nanoparticles comprise pyridine-capped binary nanoparticles prepared according to a reaction of the type:
(IIIA)(Hal)+Na 2 (VIA)→IIIA-VIA+Na(Hal).
where IB refers to an element of group IB, IIIA refers to an element of group IIIA, VIA refers to an element of group VIA and Hal refers to a halogen.
2 . The method of claim 1 wherein the reaction may be of the type:
2InI 3 +3Na 2 Se→In 2 Se 3 +6NaI
3 . The method of claim 1 wherein there is no Cu ion involved in the reaction.
4 . The method of claim 1 wherein depositing the liquid ink on a substrate; and heating the liquid ink in one or more steps to form a photovoltaic absorber layer.
5 . The method of claim 4 , wherein the substrate comprises a metal foil up to 2 meters wide.
6 . The method of claim 4 , wherein the substrate comprises of at least one material from the group consisting of: stainless steel molybdenum, and aluminum.
7 . The method of claim 4 , wherein the substrate comprises a metallized film.
8 . The method of claim 4 , wherein applying the liquid ink comprises spreading a thin film of the liquid ink over the substrate using solution based coating techniques selected from the group consisting of: web coating, spray coating, spin coating, doctor blade coating, printing techniques including contact printing, gravure printing, microgravure printing, ink-jet printing, jet deposition, and combinations thereof.
9 . The method of claim 4 , wherein applying the liquid ink comprises spreading a thin film of the liquid ink over the substrate in a roll-to-roll manner using a web coating system.
10 . The method of claim 1 wherein the non-oxide nanoparticles are added to a solvent to form a suspension.
11 . The method of claim 1 wherein the non-oxide nanoparticles are added to a solvent to form a colloidal suspension.
12 . A photovoltaic device precursor material comprising:
a liquid ink comprising:
non-oxide metal nanoparticles containing elements from group IB, non-oxide metal nanoparticles from group IIIA; and adding one or more liquid metals containing one or more elements of group IIIA, wherein the nanoparticles comprise pyridine-capped binary nanoparticles prepared according to a reaction of the type:
(IIIA)(Hal)+Na 2 (VIA)→IIIA-VIA+Na(Hal).
where IB refers to an element of group IB, IIIA refers to an element of group IIIA, VIA refers to an element of group VIA and Hal refers to a halogen;
a dispersant; and
a solvent.