METHODS FOR MAKING THIN FILM POLYCRYSTALLINE PHOTOVOLTAIC DEVICES USING ADDITIONAL CHEMICAL ELEMENT AND PRODUCTS THEREOF
Method for making a photovoltaic device and structure thereof. The method includes providing a substrate including a glass layer, a first conductive layer on the glass layer, and a cadmium sulfide layer on the first conductive layer. Additionally, the method includes depositing one or more first materials on the cadmium sulfide layer. The one or more first materials include a first quantity of chemical element cadmium and a second quantity of chemical element tellurium. Moreover, the method includes performing a first thermal treatment to at least the first quantity of chemical element cadmium, the second quantity of chemical element tellurium, and a third quantity of chemical element chlorine, so that a polycrystalline layer composed of at least cadmium telluride is formed on the cadmium sulfide layer. Also, the method includes depositing one or more second materials on a surface of the polycrystalline layer.
1 . A method for making a photovoltaic device, the method comprising:
providing a substrate including a glass layer, a first conductive layer on the glass layer, and a cadmium sulfide layer on the first conductive layer;
depositing one or more first materials on the cadmium sulfide layer, the one or more first materials including a first quantity of chemical element cadmium and a second quantity of chemical element tellurium;
performing a first thermal treatment to at least the first quantity of chemical element cadmium, the second quantity of chemical element tellurium, and a third quantity of chemical element chlorine, so that a polycrystalline layer composed of at least cadmium telluride is formed on the cadmium sulfide layer;
depositing one or more second materials on a surface of the polycrystalline layer, the one or more second materials including a fourth quantity of chemical element chlorine;
performing a second thermal treatment to at least the one or more second materials so that at least a first part of the fourth quantity of chemical element chlorine diffuses into the polycrystalline layer;
removing at least a second part of the fourth quantity of chemical element chlorine from the surface of the polycrystalline layer; and
forming a second conductive layer on the polycrystalline layer composed of at least cadmium telluride.
2 . The method of claim 1 wherein the process for depositing one or more first materials includes:
depositing at least the first quantity of chemical element cadmium and the second quantity of chemical element tellurium; and
depositing at least the third quantity of chemical element chlorine.
3 . The method of claim 2 wherein the process for depositing at least the third quantity of chemical element chlorine is performed before the process for depositing at least the first quantity of chemical element cadmium and the second quantity of chemical element tellurium.
4 . The method of claim 2 wherein the process for depositing at least the third quantity of chemical element chlorine is performed after the process for depositing at least the first quantity of chemical element cadmium and the second quantity of chemical element tellurium.
5 . The method of claim 2 wherein the process for depositing at least the third quantity of chemical element chlorine and the process for depositing at least the first quantity of chemical element cadmium and the second quantity of chemical element tellurium overlap in time.
6 . The method of claim 5 wherein the process for depositing one or more first materials includes depositing a liquid ink composed of at least one or more cadmium telluride particles and a cadmium chloride material in a solvent.
7 . The method of claim 1 wherein the process for performing a first thermal treatment includes supplying at least the third quantity of chemical element chlorine after the process for depositing one or more first materials is performed.
8 . The method of claim 7 wherein the process for supplying at least the third quantity of chemical element chlorine comprises supplying a gas-phase flux of cadmium chloride.
9 . The method of claim 1 wherein the process for depositing one or more first materials on the cadmium sulfide layer comprises depositing a liquid ink composed of at least one or more cadmium telluride particles suspended in a solvent, the one or more cadmium telluride including the first quantity of chemical element cadmium and the second quantity of chemical element tellurium.
10 . The method of claim 1 wherein the process for depositing one or more second materials includes depositing a liquid ink composed of at least a cadmium chloride material dissolved in a solvent, the cadmium chloride material including the fourth quantity of chemical element chlorine.
11 . The method of claim 1 wherein:
the first thermal treatment is performed under the atmospheric pressure at a first temperature for a first period of time; and
the second thermal treatment is performed under the atmospheric pressure at a second temperature for a second period of time.
12 . The method of claim 11 wherein:
the first temperature is higher than the second temperature; and
the first period of time is longer than the second period of time.
13 . The method of claim 1 wherein the process for providing a substrate comprises:
providing at least the first conductive layer located indirectly on the glass layer through a diffusion barrier layer; and
providing at least the cadmium sulfide layer located indirectly on the first conductive layer through a buffer layer.
14 . A method for making a photovoltaic device, the method comprising:
providing a substrate including a glass layer, a first conductive layer on the glass layer, and a cadmium sulfide layer on the first conductive layer;
depositing a first liquid ink composed of at least one or more cadmium telluride particles and a first cadmium chloride material in a first solvent;
performing a first thermal treatment to at least the one or more cadmium telluride particles and the first cadmium chloride material, so that a polycrystalline layer composed of at least cadmium telluride is formed on the cadmium sulfide layer;
depositing a second liquid ink composed of at least a second cadmium chloride material in a second solvent;
performing a second thermal treatment to at least the second cadmium chloride material so that at least a first part of the second cadmium chloride material diffuses into the polycrystalline layer;
removing at least a second part of the second cadmium chloride material from the surface of the polycrystalline layer; and
forming a second conductive layer on the polycrystalline layer composed of at least cadmium telluride.
15 . The method of claim 14 wherein:
the first thermal treatment is performed under the atmospheric pressure at a first temperature for a first period of time; and
the second thermal treatment is performed under the atmospheric pressure at a second temperature for a second period of time.
16 . The method of claim 15 wherein:
the first temperature is higher than the second temperature; and
the first period of time is longer than the second period of time.
17 . The method of claim 14 wherein the process for providing a substrate comprises:
providing at least the first conductive layer located indirectly on the glass layer through a diffusion barrier layer; and
providing at least the cadmium sulfide layer located indirectly on the first conductive layer through a buffer layer.
18 . The method of claim 14 wherein the first solvent and the second solvent are the same.
19 . A photovoltaic device, the device comprising:
a substrate including a glass layer, a first conductive layer on the glass layer, and a cadmium sulfide layer on the first conductive layer;
a polycrystalline layer composed of at least cadmium telluride on the cadmium sulfide layer, the polycrystalline layer being doped with chemical element chlorine;
a second conductive layer on the polycrystalline layer; and
an encapsulation layer on the second conductive layer;
wherein the photovoltaic device is characterized by a photovoltaic conversion efficiency that is greater than 9% under standard test conditions, an open circuit voltage that is greater than 750 mV, and a short circuit current that is greater than 20 mA/cm 2 .
20 . The photovoltaic device of claim 19 wherein the encapsulation layer includes at least a polymer layer.
21 . The photovoltaic device of claim 19 wherein:
the first conductive layer is located indirectly on the glass layer through a diffusion barrier layer; and
the cadmium sulfide layer is located indirectly on the first conductive layer through a buffer layer.
22 . A photovoltaic device, the device comprising:
a substrate including a glass layer, a first conductive layer on the glass layer, and a cadmium sulfide layer on the first conductive layer;
a polycrystalline layer composed of at least cadmium telluride on the cadmium sulfide layer, the polycrystalline layer being doped with chemical element chlorine;
a second conductive layer on the polycrystalline layer; and
an encapsulation layer on the second conductive layer;
wherein:
the polycrystalline layer includes a first surface and a second surface;
the polycrystalline layer is characterized by a porosity;
the porosity of the polycrystalline layer close to the first surface is larger than the porosity of the polycrystalline layer close to the second surface.
23 . The photovoltaic device of claim 21 wherein:
the porosity of the polycrystalline layer close to the first surface is less than 10%;
the porosity of the polycrystalline layer close to the second surface is larger than 10% but smaller than 50%.
24 . The photovoltaic device of claim 21 wherein the photovoltaic device is characterized by a photovoltaic conversion efficiency that is greater than 9% under standard test conditions, an open circuit voltage that is greater than 750 mV, and a short circuit current that is greater than 20 mA/cm 2 .