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Users may download and print one copy of any publication from the public portal for the purpose of private study or research.
You may not further distribute the material or use it for any profit-making activity or commercial gain
You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
Downloaded from orbit.dtu.dk on: Feb 02, 2019
Morphology of Copper Tin Sulfide Films Grown by Pulsed Laser Deposition at 248 and355 nm
Document VersionPublisher's PDF, also known as Version of record
Link back to DTU Orbit
Citation (APA):Ettlinger, R. B., Cazzaniga, A. C., Crovetto, A., Ravnkilde, L., Youngman, T. H., Canulescu, S., ... Schou, J.(2015). Morphology of Copper Tin Sulfide Films Grown by Pulsed Laser Deposition at 248 and 355 nm. Postersession presented at 13th Conference on Laser Ablation, Cairns, Australia.
Thin films solar cells based on Cu2ZnSnS4 (CZTS) as absorber layer have seen a rapid development leadingto a world record of 8.8% [1].
However, other p-type semiconductors with fewer elements and reduced complexity compared to CZTS arealso available, such as ternary Cu–Sn–S systems, i.e. Cu2SnS3 (CTS) [2].
Properties of CTS as absorber layer in solar cell Band gap of ~ 1.0 eV ( CZTS 1.45 eV) and absorption coefficient
comparable to CZTS (104 cm -1 ) [3].
It consists of environmentally friendly and abundant elements.
Reduced complexity compared to CZTS.
Choice of PLD The CTS absorber layer has a complex stoichiometry
Its composition needs be accurately controlled
Sn and S losses are commonly observed in CTS films, thus a SnS-enriched CTS system is also studied here.
Motivation and aimFirst CTS solar cell prepared by Pulsed Laser Deposition have reached an efficiency of 0.82%. [4]
To best of our knowledge, we were the first group to report on CTS thin films by Pulsed Laser Deposition(PLD) [5].
Ablation of CTS at 355 nm results in large droplets and rough surfaces and the aim of the study is to reducetheir size and distribution.
Here we study the influence of the laser wavelength on the size and density of the droplets using:
1. Two different wavelengths, i.e. 355 nm (Nd:YAG laser, third harmonic) and 248 nm (KrF excimer laser).
2. Two different targets, i.e. CTS and SnS enriched-CTS to compensate for losses of Sn and S in the CTSfilms
Rebecca Bolt Ettlinger1*, Andrea Cazzaniga1, Andrea Crovetto2, Lasse Ravnkilde2, Tomas Youngman2, Stela Canulescu1, Ole Hansen2, Nini Pryds3, and Jørgen Schou1
1DTU Fotonik, Technical University of Denmark, DK‐4000 Roskilde, Denmark2DTU Nanotech, Technical University of Denmark, DK‐2800 Kgs. Lyngby, Denmark3DTU Energy, Technical University of Denmark, DK‐4000 Roskilde, Denmark
The Pulsed Laser Deposition Route
Morphology of Copper Tin Sulfide Films Grown by Pulsed Laser Deposition at 248 and 355 nm
AcknowledgementThis research is supported by The Danish Council for Strategic Research
References[1] Shin Tajima et al., Applied Physics Express 8, 082302 (2015) [2] P.A. Fernandes, P.M.P. Salome, A.F. da Cunha: J. Phys. D-Appl. Phys. 21, 215403 (2010) [3] 1. N. Aihara, H. Araki, A. Takeuchi, K. Jimbo, H. Katagiri: physica status solidi (c) 7-8, 1086-1092 (2013)[4] S.A. Vanalakar, G.L. Agawane, A.S. Kamble, C.W. Hong, P.S. Patil, J.H. Kim: Solar Energy Mater. Solar Cells, 1-8 (2015) [5] R.B. Ettlinger, A. Cazzaniga, S. Canulescu, N. Pryds, J. Schou: Appl. Surf. Sci., 385-390 (2015)
Deposition rate measurements
Discussion and conclusion• SEM images reveal that CTS and SnS-enriched CTS absorber layers have droplets ranging from hundreds of
nanometers up to several micrometers. • A lower irradiation wavelength (higher photon energy) does not reduce the density or size of the droplets.• Droplets are generally Sn and S-poor suggesting losses of volatile elements during re-crystallization of the molten
agglomerates arising from the ablation process.
• Annealing reduces considerably the size and distribution of droplets; however, local non-uniformity composition may be retained in the annealed films.
• Bubbles are present on the surface of the annealed films, most probably resulting from evaporation of SnS.
• Further studies will be carried out to understand the influence of droplets on the performance of the solar cells but also to reduce their density by optimization of the PLD process
= 355 nm = 248 nm
Nd:YAG KrF excimer
= 5‐7 ns, = 10Hz ~ 20 ns, = 10Hz
A= 2.1‐2.5 mm2 A = 2.2 mm2
F= 0.4‐2.3 J/cm2 F = 0.4‐2.2 J/cm2
D = 4‐4.5 cm(target‐substrate dist.)
D = 4 cm
Deposition of Cu2SnS3 and SnS-enriched Cu2SnS3, i.e. Cu2Sn2S5Post annealing in sulfur atmopshere at 570 C using sulfur powder in a N2 gas
Surface morphology
Figure 2. SEM images (top and sideview) of as-deposited Cu2SnS3 filmson Mo-coated soda-lime glass
1 m 1 m
355 nm 248 nm
1 m 1 m
Figure 3. SEM images (top and sideview) of as-deposited SnS-enriched Cu2SnS3 films on Mo-coated soda-lime glass
355 nm 248 nm
Annealing of CTS and SnS enriched-CTS
10 μm 10 μm
1 μm 1 μm
10 μm
1 μm
355 nm 248 nm
10 μm
1 μm
Cu2SnS3 films SnS-enriched Cu2SnS3 films
355 nm 248 nm
0.0 0.5 1.0 1.5 2.0 2.50.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.10
0.11Cu2SnS3 deposition rate at 248 nm
Thi
ckne
ss /
pul
se (
nm)
Fluence (J/cm2)0.0 0.5 1.0 1.5 2.0 2.5
0.00
0.01
0.02
0.03
0.04
0.05
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0.09
0.10
0.11Cu2SnS3 deposition rate at 355 nm
Thi
ckne
ss /
pul
se (
nm)
Fluence (J/cm2)
Lower deposition rate for Cu2SnS3 at 248 nm laser than 355 nm
Higher deposition rate for SnS-enriched Cu2SnS3 than Cu2SnS3
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