Evolution of High Efficiency. Silicon Solar Cell Design

Transcription

1 Australian Centre for Advanced Photovoltaics Evolution of High Efficiency Silicon Solar Cell Design Martin A. Green University of New South Wales

2 Outline Lecture 2 1. Enter the modern era 2. Principle I Dark/Light Superposition 3. Improving emitters 4. Principle II Dark/Light Reciprocity 5. Evolution of Si cell design I 6. Light trapping 7. Evolution of Si cell design II 8. Principle III PV/LED Reciprocity 9. The future -Questions-

3 Conventional space cell Vanguard I (1958)

4 Conventional space cell Efficiency, %

5 Violet cell (1972) Light top diffusion (no dead layer) 20 Efficiency, %

6 Violet cell (1972) Light top diffusion (no dead layer) 2. Photolithographically defined top contacts 20 Efficiency, %

7 Violet cell (1972) Light top diffusion (no dead layer) 2. Photolithographically defined top contacts 3. Rear Al BSF (back surface field) Efficiency, %

8 Violet cell (1972) Light top diffusion (no dead layer) 2. Photolithographically defined top contacts 3. Rear Al BSF (back surface field) 4. Higher index AR coating Efficiency, %

9 Violet cell (1972) Efficiency, % Light top diffusion (no dead layer) 2. Photolithographically defined top contacts 3. Rear Al BSF (back surface field) 4. Higher index AR coating (also less absorbing, thinner giving violet colour

10 Violet cell (1972) Efficiency, % Light top diffusion (no dead layer) 2. Photolithographically defined top contacts 3. Rear Al BSF (back surface field) 4. Higher index AR coating (also less absorbing, thinner giving violet colour 5. Higher doped substrate (2 ohm_cm)

11 Black cell (1974) Efficiency, %

12 Black cell (1974) Efficiency, %

13 Black cell (1974) Efficiency, %

14 Black cell (1974) Efficiency, %

15 Outline Lecture 2 1. Enter the modern era 2. Principle I Dark/Light Superposition 3. Improving emitters 4. Principle II Dark/Light Reciprocity 5. Evolution of Si cell design I 6. Light trapping 7. Evolution of Si cell design II 8. Principle III PV/LED Reciprocity 9. The future -Questions-

16 Can treat light & dark separately! Superposition

17 Can treat light & dark separately! emitter base Superposition

18 Outline Lecture 2 1. Enter the modern era 2. Principle I Dark/Light Superposition 3. Improving emitters 4. Principle II Dark/Light Reciprocity 5. Evolution of Si cell design I 6. Light trapping 7. Evolution of Si cell design II 8. Principle III PV/LED Reciprocity 9. The future -Questions-

19 Re-cap: pn junction theory

20 Re-cap: pn junction theory

21 surface Re-cap: pn junction theory

22 Re-cap: pn junction theory

23 Re-cap: pn junction theory

24 Re-cap: pn junction theory

25 Re-cap: pn junction theory

26 Outline Lecture 2 1. Enter the modern era 2. Principle I Dark/Light Superposition 3. Improving emitters 4. Principle II Dark/Light Reciprocity 5. Evolution of Si cell design I 6. Light trapping 7. Evolution of Si cell design II 8. Principle III PV/LED Reciprocity 9. The future -Questions-

27 Dark/Light Reciprocity Fig. 8.1 Red book Generation rate p n Depletion region n G Region 1 Region 2 p x 1 Generation only at this plane x x' (a) Distance from surface (b)

28 Dark/Light Reciprocity Fig. 8.1 Red book Depletion n region Generation rate Fig. 8.3 Red book p n Depletion region p n p Collection probability, f c e _ x'/ln G e _ x'/le Region 1 Region 2 Figure 8.3 x 1 Generation only at this plane Distance into cell, x x x' (a) x' x Distance from surface (b)

29 Dark/Light Reciprocity N p Fig. 8.1 Red book n p f c = sinh [(W P x) / L e ] sinh (W P / L e ) Generation only at this plane (a) Collection probability, f c f c = cosh [(W P x) / L e ] cosh (W P / L e ) e Depletion n W N _ x'/ln W W P x' region Generation rate G Distance into cell, x Fig. 8.3 Red book p n Depletion region x e p _ x'/le Region 1 Region 2 Figure 8.3 x Distance from surface (b) x 1 x'

30 Re-cap: pn junction theory f c = cosh [(W P x) / L e ] cosh (W P / L e ) f c = sinh [(W P x) / L e ] sinh (W P / L e )

31 Outline Lecture 2 1. Enter the modern era 2. Principle I Dark/Light Superposition 3. Improving emitters 4. Principle II Dark/Light Reciprocity 5. Evolution of Si cell design I 6. Light trapping 7. Evolution of Si cell design II 8. Principle III PV/LED Reciprocity 9. The future -Questions-

32 MINP cell (1983) First 20% cell Efficiency, %

33 PESC cell (1984) First 20% cell Efficiency, %

34 µg-pesc cell (1985) First 20% cell Efficiency, %

35 Improved efficiency: 20% and beyond 25 Efficiency, % First 20% cell Front side fixed

36 Improved efficiency: 20% and beyond Tech Transfer Trina, Solarfun CTO Suntech/ Sunergy/ JA Solar/ Sunrise Global ANU CoE PV CoE/ Suntech CTO China Sunergy CTO CSG Solar CEO PV Centre of Excellence (PV CoE)

37 Outline Lecture 2 1. Enter the modern era 2. Principle I Dark/Light Superposition 3. Improving emitters 4. Principle II Dark/Light Reciprocity 5. Evolution of Si cell design I 6. Light trapping 7. Evolution of Si cell design II 8. Principle III PV/LED Reciprocity 9. The future -Questions-

38 Light trapping

39 Outline Lecture 2 1. Enter the modern era 2. Principle I Dark/Light Superposition 3. Improving emitters 4. Principle II Dark/Light Reciprocity 5. Evolution of Si cell design I 6. Light trapping 7. Evolution of Si cell design II 8. Principle III PV/LED Reciprocity 9. The future -Questions-

40 Improved efficiency: 22% cells 25 Stanford Uni Rear Junction Cell 20 First 20% cell Efficiency, %

41 Improved efficiency: 22% cells First 20% cell Efficiency, %

42 Improved efficiency: 25% PERL cells First 20% cell Efficiency, %

43 Outline Lecture 2 1. Enter the modern era 2. Principle I Dark/Light Superposition 3. Improving emitters 4. Principle II Dark/Light Reciprocity 5. Evolution of Si cell design I 6. Light trapping 7. Evolution of Si cell design II 8. Principle III PV/LED Reciprocity 9. The future -Questions-

44 Shockley-Queisser Shockley-Queisser Limit η max = 31% (global) = 41% (direct) Ω P = qv E G {N BB (6000K) exp(qv/kt) N BB (300K)} dedω

45 Other recombination paths

46 Black bodies (Planck) Energy distribution (kw/µm 2 /micron). E S. S S. E C. S C 2.5 Hemispherical emissive power (10 8 W-m 2 /µm) K T A. W T c K black body Q 4500 K AM0 (3X) radiation.. S = Q/T A AM1.5 radiation 3000 K (10 X) Wavelength (µm) microns

47 Shockley-Queisser η max = 31% (global) = 41% (direct) Ω P = qv E G {N BB (6000K) exp(qv/kt) N BB (300K)} dedω

48 Blackbody 300K

49 Blackbody 300K

50

51 Actual efficiency: Si cells First 20% cell Efficiency, %

52 Blackbody LED Photon Flux Emission = EQE(PV) * BB * exp(qv/kt) IQE EQE 80 Uwe Rau Physical 60 Review B 76, , 2007 EQE, IQE, R (%) Uwe Rau Physical Review B 76, , Wavelength, nm R Wavelength, nm

53 Blackbody LED 10 9 Emission = EQE(PV) * BB * exp(qv/kt) IQE EQE 80 Uwe Rau Physical Review B 76, , EQE, IQE, R (%) Photon Flux R Wavelength, nm Wavelength, nm

54 Blackbody LED 10 9 Emission = EQE(PV) * BB * exp(qv/kt) IQE EQE 80 Uwe Rau Physical Review B 76, , EQE, IQE, R (%) Photon Flux R Wavelength, nm Wavelength, nm

55 Outline Lecture 2 1. Enter the modern era 2. Principle I Dark/Light Superposition 3. Improving emitters 4. Principle II Dark/Light Reciprocity 5. Evolution of Si cell design I 6. Light trapping 7. Evolution of Si cell design II 8. Principle III PV/LED Reciprocity 9. The (near)future -Questions-

56 Improved efficiency: LDSE p- type substrate

57 Improved efficiency: 20.3% Pluto cell p- type substrate

58 Other approaches: HIT cell

59 Other approaches: EWT cell

60 Other approaches: MWT cell

61 Outline Lecture 2 1. Enter the modern era 2. Principle I Dark/Light Superposition 3. Improving emitters 4. Principle II Dark/Light Reciprocity 5. Evolution of Si cell design I 6. Light trapping 7. Evolution of Si cell design II 8. Principle III PV/LED Reciprocity 9. The (not so near)future -Questions-

62 Thermodynamic efficiency limits η (1-T A S s /E s ) = 93.3% (direct) = 73.7% (global)

63 Third generation options

64 Auger recombination c-si tandem Exp Free choice or Si

65 Si wafer-based tandem stack

66 Outline Lecture 2 1. Enter the modern era 2. Principle I Dark/Light Superposition 3. Improving emitters 4. Principle II Dark/Light Reciprocity 5. Evolution of Si cell design I 6. Light trapping 7. Evolution of Si cell design II 8. Principle III PV/LED Reciprocity 9. The future -Questions-