Photovoltaic cells with multi-band gap and applications in a low temperature polycrystalline silicon thin film transistor panel

1. A photovoltaic cell, comprising:

a first conductive layer;

a second conductive layer; and

a photovoltaic conversion layer formed between the first conductive layer and the second conductive layer, wherein the photovoltaic conversion layer has a multi-band gap, and the photovoltaic conversion layer comprises:

a first silicon-rich dielectric sub-layer formed between the first conductive layer and the second conductive layer, the first silicon-rich dielectric sub-layer having a first silicon content ratio and a first refractive index n1 corresponding to the first silicon content ratio;

a second silicon-rich dielectric sub-layer formed between the first silicon-rich dielectric sub-layer and the second conductive layer, the second silicon-rich dielectric sub-layer having a second silicon content ratio and a second refractive index n2 corresponding to the second silicon content ratio, wherein the second silicon content ratio is smaller than the first silicon content ratio, and the second refractive index n2 is smaller than the first refractive index n1; and

a third silicon-rich dielectric sub-layer formed between the second silicon-rich dielectric sub-layer and the second conductive layer, the third silicon-rich dielectric sub-layer having a third silicon content ratio and a third refractive index n3 corresponding to the third silicon content ratio, wherein the third silicon content ratio is smaller than the second silicon content ratio, and the third refractive index n3 is smaller than the second refractive index n2,

wherein the first silicon-rich dielectric sub-layer and the second silicon-rich dielectric sub-layer are substantially in contact with each other, and the second silicon-rich dielectric sub-layer and the third silicon-rich dielectric sub-layer are substantially in contact with each other; and

wherein each of the first silicon-rich dielectric sub-layer, the second silicon-rich dielectric sub-layer and the third silicon-rich dielectric sub-layer includes a plurality of silicon nanocrystals therein.

2. The photovoltaic cell of claim 1 , wherein each of the first silicon-rich dielectric sub-layer and the second silicon-rich dielectric sub-layer is formed of a material comprising silicon-rich oxide, silicon-rich nitride, silicon-rich oxy-nitride, silicon-rich carbide, or a combination of them.

3. The photovoltaic cell of claim 1 , wherein the silicon nanocrystals have a size in a range of about 1-20 nm.

4. The photovoltaic cell of claim 1 , wherein each of the first silicon-rich dielectric sub-layer, the second silicon-rich dielectric sub-layer and the third silicon-rich dielectric sub-layer is formed of a material comprising silicon-rich oxide, silicon-rich nitride, silicon-rich oxy-nitride, silicon-rich carbide, or a combination of them.

5. The photovoltaic cell of claim 1 , wherein the photovoltaic conversion layer further comprises:

(i) an amorphous silicon (a-Si) layer; and

(ii) a polycrystalline silicon (poly-Si) layer,

wherein the first silicon-rich dielectric sub-layer and the second silicon-rich dielectric sub-layer are formed between the a-Si layer and the poly-Si layer.

6. The photovoltaic cell of claim 1 , further comprising:

(i) an N-doped semiconductor layer formed between the first conductive layer and the photovoltaic conversion layer; and

(ii) a P-doped semiconductor layer formed between the second conductive layer and the photovoltaic conversion layer.

7. The photovoltaic cell of claim 1 , wherein at least one of the first and second conductive layers is formed of a transparent conductive material.

8. The photovoltaic cell of claim 1 , wherein the multi-band gap is in a range about 4.1 eV to about 1.2 eV.

9. The photovoltaic cell of claim 1 , wherein the first silicon-rich dielectric sub-layer and the second silicon-rich dielectric sub-layer substantially in contact with each other define a single junction therebetween.

10. A photovoltaic cell, comprising:

a first conductive layer;

a second conductive layer; and

a photovoltaic conversion layer formed between the first conductive layer and the second conductive layer, wherein the photovoltaic conversion layer has a multi-band gap, and the photovoltaic conversion layer comprises:

a first silicon-rich dielectric sub-layer formed between the first conductive layer and the second conductive layer, the first silicon-rich dielectric sub-layer having a first silicon content ratio and a first refractive index n1 corresponding to the first silicon content ratio;

a second silicon-rich dielectric sub-layer formed between the first silicon-rich dielectric sub-layer and the second conductive layer, the second silicon-rich dielectric sub-layer having a second silicon content ratio and a second refractive index n2 corresponding to the second silicon content ratio; and

a third silicon-rich dielectric sub-layer formed between the second silicon-rich dielectric sub-layer and the second conductive layer, the third silicon-rich dielectric sub-layer having a third silicon content ratio and a third refractive index n3 corresponding to the third silicon content ratio,

wherein the first silicon-rich dielectric sub-layer and the second silicon-rich dielectric sub-layer are substantially in contact with each other, and wherein the second silicon-rich dielectric sub-layer and the third silicon-rich dielectric sub-layer are substantially in contact with each other,

wherein the second silicon content ratio is smaller than the first silicon content ratio, and the second refractive index n2 is smaller than the first refractive index n1, and wherein the third silicon content ratio is smaller than the second silicon content ratio, and the third refractive index n3 is smaller than the second refractive index n2.

11. The photovoltaic cell of claim 10 , wherein each of the first silicon-rich dielectric sub-layer, the second silicon-rich dielectric sub-layer and the third silicon-rich dielectric sub-layer includes a plurality of silicon nanocrystals therein.

12. The photovoltaic cell of claim 11 , wherein the silicon nanocrystals have a size in a range of about 1-20 nm.

13. The photovoltaic cell of claim 10 , wherein each of the first silicon-rich dielectric sub-layer, the second silicon-rich dielectric sub-layer and the third silicon-rich dielectric sub-layer is formed of a material comprising silicon-rich oxide, silicon-rich nitride, silicon-rich oxy-nitride, silicon-rich carbide, or a combination of them.

14. The photovoltaic cell of claim 10 , wherein the photovoltaic conversion layer further comprises:

(i) an amorphous silicon (a-Si) layer; and

(ii) a polycrystalline silicon (poly-Si) layer,

wherein the first silicon-rich dielectric sub-layer and the second silicon-rich dielectric sub-layer are formed between the a-Si layer and the poly-Si layer.

15. The photovoltaic cell of claim 10 , further comprising:

(i) an N-doped semiconductor layer formed between the first conductive layer and the photovoltaic conversion layer; and

(ii) a P-doped semiconductor layer formed between the second conductive layer and the photovoltaic conversion layer.

16. The photovoltaic cell of claim 10 , wherein at least one of the first and second conductive layers is formed of a transparent conductive material.

17. The photovoltaic cell of claim 10 , wherein the multi-band gap is in a range about 4.1 eV to about 1.2 eV.

18. The photovoltaic cell of claim 10 , wherein the first silicon-rich dielectric sub-layer and the second silicon-rich dielectric sub-layer define a single junction therebetween, and the second silicon-rich dielectric sub-layer and the third silicon-rich dielectric sub-layer define a single junction therebetween.

19. A liquid crystal display (LCD) panel operably drivable by an LCD driver and illuminable by a backlight, comprising:

(a) a display area for displaying information of interest; and

(b) a photovoltaic cell positioned in an area surrounding the display area and exposed to a light and adapted for converting the optical energy of the light into an electrical energy that is supplied to the LCD driver as a driving power, wherein the photovoltaic cell comprises:

(i) a first conductive layer;

(ii) a second conductive layer; and

(iii) a photovoltaic conversion layer formed between the first conductive layer and the second conductive layer, wherein the photovoltaic conversion layer has a multi-band gap, and the photovoltaic conversion layer comprises:

a first silicon-rich dielectric sub-layer formed between the first conductive layer and the second conductive layer; the first silicon-rich dielectric sub-layer having a first silicon content ratio and a first refractive index n1 corresponding to the first silicon content ratio;

a second silicon-rich dielectric sub-layer formed between the first silicon-rich dielectric sub-layer and the second conductive layer, the second silicon-rich dielectric sub-layer having a second silicon content ratio and a second refractive index n2 corresponding to the second silicon content ratio, wherein the second silicon content ratio is smaller than the first silicon content ratio, and the second refractive index n2 is smaller than the first refractive index n1; and

a third silicon-rich dielectric sub-layer formed between the second silicon-rich dielectric sub-layer and the second conductive layer, the third silicon-rich dielectric sub-layer having a third silicon content ratio and a third refractive index n3 corresponding to the third silicon content ratio, wherein the third silicon content ratio is smaller than the second silicon content ratio, and the third refractive index n3 is smaller than the second refractive index n2,

wherein the first silicon-rich dielectric sub-layer and the second silicon-rich dielectric sub-layer are substantially in contact with each other, and the second silicon-rich dielectric sub-layer and the third silicon-rich dielectric sub-layer are substantially in contact with each other; and

wherein each of the first silicon-rich dielectric sub-layer, the second silicon-rich dielectric sub-layer and the third silicon-rich dielectric sub-layer includes a plurality of silicon nanocrystals therein.

20. The LCD panel of claim 19 , wherein the photovoltaic conversion layer further comprises:

(i) an amorphous silicon (a-Si) layer formed between the first conductive layer and the first silicon-rich dielectric sub-layer; and

(ii) a polycrystalline silicon (poly-Si) layer formed between the second silicon-rich dielectric sub-layer and the second conductive layer.

21. The LCD panel of claim 20 , wherein each of the-first silicon-rich dielectric sub-layer and the second silicon-rich dielectric sub-layer is formed of a material comprising silicon-rich oxide, silicon-rich nitride, silicon-rich oxy-nitride, silicon-rich carbide, or a combination of them.

22. The LCD panel of claim 21 , wherein the silicon nanocrystals have a size in a range of about 1-20 nm.

23. The LCD panel of claim 19 , wherein the display area comprises a plurality of low temperature polycrystalline silicon thin film transistors (LTPS-TFTs).

24. A display panel having a plurality of pixels arranged in the form of matrix, each pixel comprising:

(a) an active area for displaying information of interest;

(b) a switch area having one or more switch elements; and

(c) a photovoltaic cell formed between the active area and the switch area, wherein the photovoltaic cell has a photovoltaic conversion layer with a multi-band gap, and the photovoltaic conversion layer comprises:

a first silicon-rich dielectric sub-layer formed between the first conductive layer and the second conductive layer; the first silicon-rich dielectric sub-layer having a first silicon content ratio and a first refractive index n1 corresponding to the first silicon content ratio;

a second silicon-rich dielectric sub-layer formed between the first silicon-rich dielectric sub-layer and the second conductive layer, the second silicon-rich dielectric sub-layer having a second silicon content ratio and a second refractive index n2 corresponding to the second silicon content ratio, wherein the second silicon content ratio is smaller than the first silicon content ratio, and the second refractive index n2 is smaller than the first refractive index n1; and

a third silicon-rich dielectric sub-layer formed between the second silicon-rich dielectric sub-layer and the second conductive layer, the third silicon-rich dielectric sub-layer having a third silicon content ratio and a third refractive index n3 corresponding to the third silicon content ratio, wherein the third silicon content ratio is smaller than the second silicon content ratio, and the third refractive index n3 is smaller than the second refractive index n2,

wherein the first silicon-rich dielectric sub-layer and the second silicon-rich dielectric sub-layer are substantially in contact with each other, the second silicon-rich dielectric sub-layer and the third silicon-rich dielectric sub-layer are substantially in contact with each other, and define a single junction therebetween; and

wherein each of the first silicon-rich dielectric sub-layer, the second silicon-rich dielectric sub-layer and the third silicon-rich dielectric sub-layer includes a plurality of silicon nanocrystals therein.

25. The display panel of claim 24 , wherein the photovoltaic conversion layer comprises:

(i) an amorphous silicon (a-Si) layer formed between the first conductive layer and the first silicon-rich dielectric sub-layer; and

(ii) a polycrystalline silicon (poly-Si) layer formed between the second silicon-rich dielectric sub-layer and the second conductive layer.

26. The display panel of claim 25 , wherein the silicon nanocrystals have a size in a range of about 1-20 nm.