High-throughput printing of semiconductor precursor layer from chalcogenide microflake particles
Methods and devices are provided for high-throughput printing of semiconductor precursor layer from microflake particles. In one embodiment, the method comprises of transforming non-planar or planar precursor materials in an appropriate vehicle under the appropriate conditions to create dispersions of planar particles with stoichiometric ratios of elements equal to that of the feedstock or precursor materials, even after settling. In particular, planar particles disperse more easily, form much denser coatings (or form coatings with more interparticle contact area), and anneal into fused, dense films at a lower temperature and/or time than their counterparts made from spherical nanoparticles. These planar particles may be microflakes that have a high aspect ratio. The resulting dense film formed from microflakes is particularly useful in forming photovoltaic devices. In one embodiment, at least one set of the particles in the ink may be inter-metallic flake particles (microflake or nanoflake) containing at least one group IB-IIIA inter-metallic alloy phase.
1. A method comprising:
formulating an ink of particles wherein about 50% or more of all the particles are microflakes each containing at least one element from group IB, IIIA and/or VIA and having a non-spherical, planar shape, wherein overall amounts of elements from group IB, IIIA and/or VIA contained in the ink are such that the ink has a desired stoichiometric ratio of the elements;
coating a substrate with the ink to form a precursor layer; and
processing the precursor layer in a suitable atmosphere to form a dense film; wherein at least one set of the particles in the ink are inter-metallic microflake particles containing at least one group IB-IIIA inter-metallic alloy phase.
2. The method of claim 1 wherein the dense film is used in the formation of a semiconductor absorber for a photovoltaic device.
3. The method of claim 2 wherein the planar shape of the microflakes results in grain sizes of at least about 2.0 μm in at least one dimension in the semiconductor absorber of a photovoltaic device.
4. The method of claim 2 wherein the planar shape of the microflakes results in grain sizes of at least about 1.0 μm in at least one dimension in the semiconductor absorber of a photovoltaic device.
5. The method of claim 2 wherein the planar shape of the microflakes results in grain sizes of at least about 0.5 μm in at least one dimension in the semiconductor absorber of a photovoltaic device.
6. The method of claim 1 wherein substantially all of the particles have a non-spherical, planar shape.
7. The method of claim 1 wherein the particles comprise of microflakes and nanoflakes.
8. The method of claim 1 wherein at least about 75% or more of a total weight of all the particles are microflakes.
9. The method of claim 1 wherein the microflakes are of random planar shape and/or a random size distribution.
10. The method of claim 1 wherein the microflakes are of a non-random planar shape and/or a non-random size distribution.
11. The method of claim 1 wherein the microflakes each have a length less than about 5 microns and greater than about 0.5 microns.
12. The method of claim 1 wherein the microflakes each have a length between about 3 microns and 0.5 microns.
13. The method of claim 1 wherein the microflakes each have a thickness less than about 100 nm.
14. The method of claim 1 wherein the microflakes each have a thickness less than about 20 nm.
15. The method of claim 1 wherein the microflakes have length of less than about 2 microns and a thickness of less than 100 nm.
16. The method of claim 1 wherein the microflakes have length of less than about 1 microns and a thickness of less than 50 nm.
17. The method of claim 1 wherein the microflakes have an aspect ratio of at least about 10 or more.
18. The method of claim 1 wherein the microflakes have an aspect ratio of at least about 15 or more.
19. The method of claim 1 wherein the microflakes are substantially oxygen-free.
20. The method of claim 1 wherein the particles include chalcogenide particles.
21. The method of claim 1 wherein the particles include selenide particles.
22. A method comprising:
formulating an ink of particles wherein a majority of the particles are microflakes each containing at least one element from group IB, IIIA and/or VIA and having a non-spherical, planar shape, wherein the overall amounts of the elements from group IB, IIIA and/or VIA contained in the ink are such that the ink has a desired stoichiometric ratio of the elements;
coating a substrate with the ink to form a precursor layer; and
processing the precursor layer to form a dense film for growth of a semiconductor absorber of a photovoltaic device;
wherein at least one set of the particles in the ink are inter-metallic microflake particles containing at least one group IB-IIIA inter-metallic alloy phase.