SEMICONDUCTOR MATERIAL SURFACE TREATMENT WITH LASER
A photovoltaic device and its method of manufacture are disclosed. The device is formed by forming a window layer over a substrate, forming an absorber layer over the window layer, and annealing the absorber layer using a laser beam to remove contaminants from the surface of the absorber layer and/or to reduce the thickness of the absorber layer.
1 . A method of manufacturing a photovoltaic device, the method comprising:
forming a window layer over a substrate;
forming an absorber layer over the window layer; and
annealing the absorber layer using a laser beam to remove contaminants from the surface of the absorber layer and/or to reduce the thickness of the absorber layer.
2 . The method of claim 1 , wherein the absorber layer comprises cadmium telluride.
3 . The method of claim 1 , wherein the window layer comprises cadmium sulfide.
4 . The method of claim 1 , wherein the absorber layer comprises at least one of copper indium gallium (di)selenide, amorphous silicon, polysilicon, monocrystalline silicon, gallium arsenide.
5 . The method of claim 1 , wherein a top surface of the absorber layer is ablated during the laser annealing.
6 . The method of claim 1 , wherein a roughness of a top surface of the absorber layer is reduced during the laser annealing.
7 . The method of claim 1 , wherein the thickness of the absorber layer is from greater than about 1500 nm to about 10000 nm prior to the laser annealing.
8 . The method of claim 1 , wherein the thickness of the absorber layer is from about 700 nm to about 1500 nm subsequent to the laser annealing.
9 . The method of claim 1 , wherein the laser beam has a wavelength of about 495 nm to about 570 nm.
10 . The method of claim 1 , wherein the laser beam has a wavelength of about 450 nm to about 495 nm.
11 . The method of claim 1 , wherein the laser beam has a wavelength of about 200 nm to about 450 nm.
12 . The method of claim 1 , further comprising at least one of doping the absorber layer with a dopant prior to the laser annealing, and conducting a cadmium chloride treatment after the formation of the absorber layer and prior to the laser annealing.
13 . The method of claim 12 , wherein the absorber layer is doped with copper prior to the laser annealing.
14 . The method of claim 1 , wherein the laser annealing is conducted in a gas environment comprising at least one inert gas.
15 . The method of claim 1 , wherein the laser beam is pulsed.
16 . The method of claim 1 , wherein the laser beam is continuous.
17 . The method of claim 1 , further comprising forming a zinc telluride layer over the absorber layer subsequent to the laser annealing.
18 . The method of claim 17 , further comprising forming a back contact over the zinc telluride layer.
19 . The method of claim 1 , further comprising forming a back contact over the absorber layer subsequent to the laser annealing.
20 . A method of manufacturing a photovoltaic device, the method comprising:
forming a layer comprising cadmium sulfide over a substrate;
forming a layer comprising cadmium telluride over the cadmium sulfide layer;
conducting a cadmium chloride treatment on the cadmium telluride layer; and
annealing the cadmium telluride layer using a laser beam to remove contaminants from the surface of the cadmium telluride layer and/or to reduce the thickness of the cadmium telluride layer.
21 . The method of claim 20 , wherein a top surface of the cadmium telluride layer is ablated during laser annealing.
22 . The method of claim 20 , wherein a roughness of a top surface of the cadmium telluride layer is reduced during the laser annealing.
23 . The method of claim 20 , wherein the thickness of the cadmium telluride layer is from greater than about 1500 nm to about 10000 nm prior to the laser annealing.
24 . The method of claim 20 , wherein the thickness of the cadmium telluride layer is from about 700 nm to about 1500 nm subsequent to the laser annealing.
25 . The method of claim 20 , further comprising doping the cadmium telluride layer with a dopant prior to the laser annealing.
26 . The method of claim 25 , wherein the cadmium telluride layer is doped with copper prior to the laser annealing.
27 . The method of claim 20 , wherein the laser beam has a wavelength of about 495 nm to about 570 nm.
28 . The method of claim 20 , wherein the laser beam has a wavelength of about 450 nm to about 495 nm.
29 . The method of claim 20 , wherein the laser beam has a wavelength of about 200 nm to about 450 nm.
30 . A photovoltaic device comprising:
a window layer over the transparent conductive layer;
an absorber layer over the window layer, the absorber layer having a laser treated surface.
31 . The device of claim 30 , wherein the absorber layer comprises cadmium telluride.
32 . The device of claim 30 , wherein the window layer comprises cadmium sulfide.
33 . The device of claim 30 , wherein the absorber layer comprises at least one of copper indium gallium (di)selenide, amorphous silicon, polysilicon, monocrystalline silicon, gallium arsenide.
34 . The device of claim 30 , wherein the absorber layer contains a dopant.
35 . The device of claim 34 , wherein the dopant comprises copper.
36 . The device of claim 30 , further comprising a zinc telluride layer over the absorber layer.
37 . The device of claim 36 , further comprising a back contact over the zinc telluride layer.
38 . The device of claim 30 , further comprising a back contact over the absorber layer.
39 . The device of claim 30 , wherein the absorber layer is substantially free of contaminants.
40 . The device of claim 30 , wherein the absorber layer has a thickness of less than about 1500 nm and is substantially free of pinholes.