Cu-depleted patches induced by presence of K during growth of CIGS absorbers

Citation for the original published paper:

Donzel-Gargand, O., Thersleff, T., Keller, J., Törndahl, T., Larsson, F. et al. (2017) Cu-depleted patches induced by presence of K during growth of CIGS absorbers.

In:

N.B. When citing this work, cite the original published paper.

Permanent link to this version:

http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-335110

Olivier Donzel-Gargand ^a

CIGS absorbers

Introduction

Results &

discussion Conclusion

Highlights

• no K during the CIGS co-evaporation

2 0,2 µm STEM ADF Cu

STEM ADF Cu

0.1 µm

CIGS layer

• K provided during the CIGS co-evaporation

Introduction

Results &

discussion Conclusion

CIGS co-evaporation profile

• Se in excess

• Ga-rich start

• Cu poor/rich/poor

Cu-rich

Introduction

Results &

discussion Conclusion

Sample description

• PDT: 350˚C

• 17% < η <18,4%

(without ARC)

4

Alkali barrier Mo

CIGS

CdS TCO

K-rich Glass

PDT:

none

PDT:

none / KF / RbF

Mo

CIGS

CdS TCO

K-rich Glass

NaF

Introduction

Results &

discussion Conclusion

Sample preparation

• Ga-based Focused Ion Beam (FIB)

– 30kV – 100pA – 5kV – 50pA

ion view

e- view

Introduction

Results &

discussion Conclusion

FIB damages

Cu -> Cd Cd -> Cu

6

After the intense repolish: (very close area)

0 . 1 µ m Cu

0 . 1 µ m

Cd

1

0 . 1 µ m

Cu

0 . 1 µ m

0 . 1 µ m

Cd

2

Beam settings

30kV 100pA

5kV 50pA

Introduction

Results &

discussion Conclusion

STEM EELS analysis

• Scanning Transmission Electron Microscopy

• Electron Energy Loss Spectroscopy

X-ray Light Electrons

δE E

L K

Introduction

Results &

discussion Conclusion

8

R.F. Egerton, Electron Energy-Loss Spectroscopy in the Electron Microscope, Springer US, Boston, MA, 2011. doi:10.1007/978-1-4419-9583-4.

Ionisation edges

STEM EELS analysis

Introduction

Results &

discussion Conclusion

K-rich glass / no PDT

Introduction

Results &

discussion Conclusion

10

K-rich glass / RbF PDT

Introduction

Results &

discussion Conclusion

Raman

Introduction

Results &

discussion Conclusion

Elemental gradient

12

Mo

CIGS

TCO CdS

K-rich Glass Mo

CIGS

TCO CdS

K-rich Glass

Cu/III maps

Introduction

Results &

discussion Conclusion

Discussion: patch formation

• Cu-rich to Cu-poor stage

– Cu _2-x Se clusters

– 2 phases growing in parallel

Cu-rich

Introduction

Results &

discussion Conclusion

Conclusions

• Presence of K

– Lower Ga/In inter-diffusion

– K incorporation in the CIGS lattice – Cu-depleted patches

– OVC (Raman)

14

• We acknowledge funding from the Swedish Energy Agency,

EU-project ARCIGS-M and the Swedish Science Council.

Introduction

Results &

discussion Conclusion Annexes

Analysis

• STEM

– Scanning Transmission Electron Microscopy

• EELS

– Energy Electron Loss Spectroscopy

16