Laser-Crystallised Thin-Film Polycrystalline Silicon Solar Cells - - PowerPoint PPT Presentation

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Laser-Crystallised Thin-Film Polycrystalline Silicon Solar Cells Jonathon Dore SPREE Research Seminar - 27th June, 2013 Contents Introduction motivation for thin-film Thin-film PV technologies Diode laser crystallised thin-film

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SLIDE 1

Laser-Crystallised Thin-Film Polycrystalline Silicon Solar Cells

Jonathon Dore SPREE Research Seminar - 27th June, 2013

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SLIDE 2
  • Introduction – motivation for thin-film
  • Thin-film PV technologies
  • Diode laser crystallised thin-film pc-Si

– Material and device preparation – Intermediate layers – Stability – Other current work – Near-term priorities for future work – Long-term priorities for future work

Contents

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SLIDE 3
  • Introduction – motivation for thin-film
  • Thin-film PV technologies
  • Diode laser crystallised thin-film pc-Si

– Material and device preparation – Intermediate layers – Stability – Other current work – Near-term priorities for future work – Long-term priorities for future work

Contents

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SLIDE 4
  • 1. Introduction

GTM Research

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SLIDE 5
  • Introduction – motivation for thin-film
  • Thin-film PV technologies
  • Diode laser crystallised thin-film pc-Si

– Material and device preparation – Intermediate layers – Stability – Other current work – Near-term priorities for future work – Long-term priorities for future work

Contents

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SLIDE 6
  • Commercial

– CdTe – CIGS – a-Si/µc-Si

  • Research

– CZTS – OPV – Thin crystalline silicon

  • Wafer transfer
  • Thin polycrystalline
  • 2. Thin-Film PV Technologies
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SLIDE 7
  • Solid Phase

– SPC – AIC

  • Liquid Phase

– ZMR – EBC – LC

  • UV
  • Visible
  • IR
  • 3. Thin Polycrystalline Si
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SLIDE 8
  • Introduction – motivation for thin-film
  • Thin-film PV technologies
  • Diode laser crystallised thin-film pc-Si

– Material and device preparation – Intermediate layers – Stability – Other current work – Near-term priorities for future work – Long-term priorities for future work

Contents

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SLIDE 9
  • Introduction – motivation for thin-film
  • Thin-film PV technologies
  • Diode laser crystallised thin-film pc-Si

– Material and device preparation – Intermediate layers – Stability – Other current work – Near-term priorities for future work – Long-term priorities for future work

Contents

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SLIDE 10
  • 4. Material Preparation

808 nm CW LIMO diode laser 12 mm x 170 µm

H H H H H H

3 mm ~150 nm ~10 µm p- poly-Si Glass 5x5 cm2 diffused n+ B-doped Intermediate layer undoped a-Si

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SLIDE 11
  • Many Σ3 twin boundaries
  • Defect density < 5e7 cm-2
  • Mobility of 300-450 at ~1e16 cm-3
  • 5. Grain structure

Optical microscope TEM

30 nm

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SLIDE 12
  • 6. Device Fabrication

Intermediate layer Glass n contact pad p- n+ Resist Aluminium p contact pad Cell area = 1 cm2

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SLIDE 13
  • 7. Light IV
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SLIDE 14
  • 8. Improvement path

6 7 8 9 10 11 12 Jul-2011 Oct-2011 Jan-2012 Apr-2012 Jul-2012 Oct-2012 Jan-2013 Apr-2013 Jul-2013 Record Efficiency [%]

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SLIDE 15
  • 8. Improvement path

6 7 8 9 10 11 12 Jul-2011 Oct-2011 Jan-2012 Apr-2012 Jul-2012 Oct-2012 Jan-2013 Apr-2013 Jul-2013 Record Efficiency [%]

First devices with SiOx IL

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SLIDE 16
  • 8. Improvement path

6 7 8 9 10 11 12 Jul-2011 Oct-2011 Jan-2012 Apr-2012 Jul-2012 Oct-2012 Jan-2013 Apr-2013 Jul-2013 Record Efficiency [%]

First devices with SiOx IL SiOx/SiCx/ SiOx IL

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SLIDE 17
  • 8. Improvement path

6 7 8 9 10 11 12 Jul-2011 Oct-2011 Jan-2012 Apr-2012 Jul-2012 Oct-2012 Jan-2013 Apr-2013 Jul-2013 Record Efficiency [%]

First devices with SiOx IL SiOx/SiCx/ SiOx IL SiOx/SiNx/ SiOx IL

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SLIDE 18
  • 8. Improvement path

6 7 8 9 10 11 12 Jul-2011 Oct-2011 Jan-2012 Apr-2012 Jul-2012 Oct-2012 Jan-2013 Apr-2013 Jul-2013 Record Efficiency [%]

First devices with SiOx IL SiOx/SiCx/ SiOx IL SiOx/SiNx/ SiOx IL improved SiOx/SiNx / SiOx IL; Rear texture

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SLIDE 19
  • Introduction – motivation for thin-film
  • Thin-film PV technologies
  • Diode laser crystallised thin-film pc-Si

– Material and device preparation – Intermediate layers – Stability – Other current work – Near-term priorities for future work – Long-term priorities for future work

Contents

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SLIDE 20
  • 10. Intermediate Layer

Intermediate layer Glass n contact pad p- n+ Resist Aluminium p contact pad Cell area = 1 cm2

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SLIDE 21
  • 10. Intermediate Layer
  • Wetting layer
  • Dopant source
  • Contamination barrier
  • Stable > 1414C
  • Transparent anti-reflection coating (ARC)
  • Passivation layer

Intermediate layer

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SLIDE 22
  • 11. Materials of Interest
  • SiCx
  • SiNx
  • SiOx
  • Layers deposited by RF sputtering or PECVD
  • 10-200 nm thick
  • Either alone or in stacks
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SLIDE 23

Intermediate Layer

  • Wetting layer
  • Dopant source
  • Contamination barrier
  • Stable > 1414C
  • Transparent anti-reflection coating (ARC)
  • Passivation layer

Intermediate layer

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SLIDE 24
  • 12. Wetting and crystallisation
  • Laser energy
  • Int. layer

Process range None

13 J/cm²

SiOx

194 J/cm²

SiNx

220 J/cm²

SiOx/SiCx stack

246 J/cm²

Too low (nc regions) Just right Too high (dewetting)

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SLIDE 25
  • 13. Wetting and crystallisation
  • Laser energy
  • Int. layer

Process range None

13 J/cm²

SiOx

194 J/cm²

SiNx

220 J/cm²

SiOx/SiCx stack

246 J/cm²

  • SiNx layers result in pinholes in Si at

high laser energies Transmission micrograph

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SLIDE 26

Intermediate Layer

  • Wetting layer
  • Dopant source
  • Contamination barrier
  • Stable > 1414C
  • Transparent anti-reflection coating (ARC)
  • Passivation layer

Intermediate layer

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SLIDE 27
  • 14. Dopant source

p- poly-Si Glass 5x5 cm2 B-doped Intermediate layer SiOx/SiNx/SiOx stack undoped a-Si

B B B B B B

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SLIDE 28
  • 15. Dopant source
  • Uniform region created during molten phase

1.E+15 1.E+16 1.E+17 1.E+18 1.E+19 1.E+20 6 7 8 9 B conc. (cm-3) Depth (µm) 80nm SiOx lowly doped Si marker (arbitrary units)

IL/Glass Silicon

  • p+ region at interface?
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SLIDE 29
  • 16. Dopant source
  • p+ region at interface?
  • Spreading resistance shows no p+
  • Inversion layer?
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SLIDE 30

Intermediate Layer

  • Wetting layer
  • Dopant source
  • Contamination barrier
  • Stable > 1414C
  • Transparent anti-reflection coating (ARC)
  • Passivation layer

Intermediate layer

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SLIDE 31
  • 17. Contamination Barrier
  • Problem is blocking B from glass!
  • SiOx best barrier
  • Can use SiOx/SiCx or SiOx/SiNx stacks

0.1 1.0 10.0 100.0 1000.0 No IL SiOx (10nm) SiOx (80nm) SiOx (200nm) SiNx (80nm) SiCx (14nm) SiCx (140nm) Sheet conductance (mS)

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SLIDE 32

1.E+14 1.E+15 1.E+16 1.E+17 1.E+18 3 4 5 6 7 8 9 Fe conc. (cm-3) Depth (µm) Grain boundary, no IL

IL/Glass

1.E+14 1.E+15 1.E+16 1.E+17 1.E+18 3 4 5 6 7 8 9 Fe conc. (cm-3) Depth (µm) Grain boundary, SiOx IL

IL/Glass

1.E+14 1.E+15 1.E+16 1.E+17 1.E+18 3 4 5 6 7 8 9 Fe conc. (cm-3) Depth (µm) Crystal grain, no IL

IL/Glass

  • 18. Contamination Barrier
  • Iron can also diffuse from glass
  • Iron found at silicon grain boundary when no IL used
  • No iron when SiOx IL used

32

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SLIDE 33

Intermediate Layer

  • Wetting layer
  • Dopant source
  • Contamination barrier
  • Stable > 1414C
  • Transparent anti-reflection coating (ARC)
  • Passivation layer

Intermediate layer

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SLIDE 34
  • 19. Stability
  • Thick SiCx or SiNx layers cause wrinkling at the glass

surface

  • Visible in reflection micrographs at IL interface viewed

through the glass 140nm SiCx 80nm SiNx 80nm SiOx 14nm SiCx No IL

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SLIDE 35
  • 20. Stability
  • Nitrogen from SiNx layer diffuses into Si during crystallisation
  • N conc in Si when SiCx and SiOx used likely from atmosphere
  • No excess C from SiCx or O from SiOx
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SLIDE 36

Intermediate Layer

  • Wetting layer
  • Dopant source
  • Contamination barrier
  • Stable > 1414C
  • Transparent anti-reflection coating (ARC)
  • Passivation layer

Intermediate layer

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SLIDE 37
  • 21. Transparent ARC

20 40 60 80 300 500 700 900 1100 Absorption (%) Wavelength (nm) SiCx (47 nm, n=2.9) SiCx (14 nm, n=2.9) SiNx (80 nm, n=2.1) SiOx (70 nm, n=1.5) BSG (n=1.5)

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SLIDE 38
  • 22. Transparent ARC

20 40 60 80 300 500 700 900 1100 Absorption (%) Wavelength (nm) SiCx (47 nm, n=2.9) SiCx (14 nm, n=2.9) SiNx (80 nm, n=2.1) SiOx (70 nm, n=1.5) BSG (n=1.5) SiNx (50 nm reactively sputtered , n=2.0)

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SLIDE 39

Intermediate Layer

  • Wetting layer
  • Dopant source
  • Contamination barrier
  • Stable > 1414C
  • Transparent anti-reflection coating (ARC)
  • Passivation layer

Intermediate layer

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SLIDE 40
  • 23. Passivation Layer

80nm SiOx (n ≈ 1.5) 20 nm SiCx (n=2.9) 80nm SiOx 70 nm SiNx (n=2.1) 80nm SiOx

Silicon IL Glass

  • Single- and double-layer stacks
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SLIDE 41
  • 24. Passivation Layer
  • Poor front

surface for SiOx/SiCx

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SLIDE 42
  • 25. Passivation Layer

15 nm SiOx 20 nm SiCx 80nm SiOx 15 nm SiOx 70 nm SiNx 80nm SiOx

  • triple-layer stacks
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SLIDE 43
  • 26. Passivation Layer
  • Surface SiOx

improves IQE

  • ONO still not

ideal

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SLIDE 44
  • 26. Passivation Layer
  • Surface SiOx

improves IQE

  • ONO still not

ideal

  • Optimised ONO

(with reactive sputtering) better

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SLIDE 45
  • 26. Passivation Layer
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SLIDE 46
  • Introduction – motivation for thin-film
  • Thin-film PV technologies
  • Diode laser crystallised thin-film pc-Si

– Material and device preparation – Intermediate layers – Stability – Other current work – Near-term priorities for future work – Long-term priorities for future work

Contents

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SLIDE 47
  • 27. Stability

JSC mA/cm2 VOC mV FF % η % Baked 27.6 585 72.4 11.7

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SLIDE 48
  • 27. Stability

JSC mA/cm2 VOC mV FF % η % Baked 27.6 585 72.4 11.7 Degraded 27.7 572 62.9 10.0

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SLIDE 49
  • 28. Stability
  • Occurs in dark
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SLIDE 50
  • 28. Stability
  • Best stabilised efficiency = 10.4%
  • Occurs in dark
  • Related to absorber

doping

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SLIDE 51
  • 29. Selective p+ (Chaho Ahn)
  • Degradation likely due to

poor contact with lightly-doped absorber

p- 10e16 cm-3

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SLIDE 52
  • 29. Selective p+ (Chaho Ahn)
  • Degradation likely due to

poor contact with lightly-doped absorber

  • Solution: selective p+ under

absorber contact

p+

p- 10e16 cm-3

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SLIDE 53
  • 30. Selective p+ (Chaho Ahn)

Cell JSC [mA/cm2] VOC [mV] FF [%] η [%] Baseline (initial) 23.6 524 62.3 7.7 Baseline (delayed) 23.9 434 46.4 4.7 Selective p+ (initial) 24.4 555 56.2 7.6 Selective p+ (delayed) 24.2 559 56.9 7.7

  • Data for cells with SiOx intermediate layer
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SLIDE 54
  • Introduction – motivation for thin-film
  • Thin-film PV technologies
  • Diode laser crystallised thin-film pc-Si

– Material and device preparation – Intermediate layers – Stability – Other current work – Near-term priorities for future work – Long-term priorities for future work

Contents

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SLIDE 55
  • 31. Rear Texture (Zamir Pakhuruddin)
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SLIDE 56
  • 32. Rear Texture (Zamir Pakhuruddin)

AFM RMS = 78 nm Absorption without rear reflector or ARC

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SLIDE 57
  • 33. Rear Texture (Zamir Pakhuruddin)
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SLIDE 58
  • 33. Rear Texture (Zamir Pakhuruddin)
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SLIDE 59
  • 34. Suns-VOC
  • Measured prior to metallisation
  • Mostly n=1 recombination
  • Measured after metallisation
  • Significant RSH ~ 500 Ohms.cm2 and n = 2 influence
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SLIDE 60
  • 35. Dark Lock-In Thermography
  • DLIT shows hotspot at Si crack (shown for neighbouring cell)
  • Same in forward and reverse bias
  • Ohmic shunt
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SLIDE 61
  • 36. Crack-free crystallisation (Jialiang Huang)

Scan direction 12 mm 12 mm Standard process “Crack-free” process

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SLIDE 62
  • 37. Grain orientation control (Jae Sung Yun)

111 100 110

Standard Process 100 nm SiOx Capping Layer Position 1 Position 2 Position 3 Inverse pole orientation map

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SLIDE 63
  • RTP diffusion

Expensive Slow Causes glass softening Exacerbates cracks Large process window ?

  • 38. Laser diffusion (Miga Jung)

100 150 200 250 300 350 1 2 3 4 5 Sheet Resistance Sample Strip # RTA sample #1 RTA sample #2 Laser Diffused sample

  • Laser diffusion

Cheap Fast No effect on glass No effect on cracks Process window ?

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SLIDE 64
  • Introduction – motivation for thin-film
  • Thin-film PV technologies
  • Diode laser crystallised thin-film pc-Si

– Material and device preparation – Intermediate layers – Stability – Other current work – Near-term priorities for future work – Long-term priorities for future work

Contents

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SLIDE 65
  • 39. Near-Term Priorities for Future Work
  • Transfer processes to TETB
  • Improve bulk passivation
  • Improve surface passivation
  • Identify and address device fabrication losses

– E.g. Cell isolation scribes

  • Investigate alternative junction formation

– Heterojunction – Other?

  • Plasmonic light-trapping?
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SLIDE 66
  • Introduction – motivation for thin-film
  • Thin-film PV technologies
  • Diode laser crystallised thin-film pc-Si

– Material and device preparation – Intermediate layers – Stability – Other current work – Near-term priorities for future work – Long-term priorities for future work

Contents

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SLIDE 67

* Mu Mult lti i wa wafe fer r s spo pot p pri rice ce = $0 = $0.84 .84/wafer /wafer @ eff @ eff = 1 = 17% 7%  $0. 0.20 20/W /W * BS BSG G ~ $2 ~ $20/ 0/m² m² a abo bove ve s stan andar dard d g gla lass ss @ ef @ eff f = = 12 12% %  $0. 0.17/ 17/W * Ne Need ed to to in incr creas ease e e eff ff an and/ d/or r us use st e stan andar dard d gl glas ass

  • 40. Simple economics
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SLIDE 68
  • Clean
  • Deposit
  • Scribe
  • Clean
  • Deposit
  • Scribe
  • Deposit
  • Scribe
  • Module assembly
  • 41. Process sequence
  • Clean
  • Deposit
  • Crystallise
  • Coat
  • Diffuse
  • Etch
  • Hydrogenate
  • Scribe
  • Coat
  • Bake
  • Inkjet
  • Etch
  • Expose
  • Bake
  • Inkjet
  • Clean
  • Bake
  • Clean
  • Deposit
  • Scribe
  • Bake
  • Module Assembly
  • Typical TF-Si
  • Laser-crystallised TF-Si
  • Need to

simplify contacting scheme

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SLIDE 69
  • 42. Conclusions
  • Laser-crystallised poly-Si solar cell reaching 11.7% efficiency
  • Exceeds record for thin-film poly-Si
  • Short-term, recoverable degradation
  • Selective p+ metallisation

makes stable cells

  • Performance improvements

mostly due to intermediate layer

  • Many more opportunities

for further improvement

6 7 8 9 10 11 12 Jul-2011 Oct-2011 Jan-2012 Apr-2012 Jul-2012 Oct-2012 Jan-2013 Apr-2013 Jul-2013