7 european kesteriteworkshop overview

CONFIDENTIAL – INTERNAL USE

Organized by

Funded by

7TH EUROPEAN KESTERITE WORKSHOP

OVERVIEW

CONFIDENTIAL – INTERNAL USE2


SESSION 1 – IMPACT OF GE ON ABSORBER FORMATION

Thomas Schnabel, ZSW

3

Cu2ZnSnSxSe4-x

12.6 % (10.3% ZSW)

Cu2ZnGeSxSe4-x

(DMSO)

3.3 %

Poor reproducibility

Cu2ZnGeSxSe4-x

(H2O)

2.1 %

Strong C-residues

Cu2ZnGeSxSe4-x

(DMF)

6.0 %

Very homogeneous

Cu2ZnSiySn1-ySxSe4-x

No efficiencies

Mostly secondary phases


SESSION 1 – IMPACT OF GE ON ABSORBER FORMATION

Sergio Giraldo, IREC

Ge doping strategies lead to an improved performance of CZTSe solar cells compared to our

former methodology without using Ge:

Ge front nanolayer: VOC increase

Ge front+back approach: JSC increase (Eff ~10 %)

Guy Brammertz, imec

Large grains and good crystallinity with little secondary phases can be obtained

Substrate type and metal stacking order have a large influence on the absorber properties

Best solar cell fabricated up to date has an efficiency of 5.5 %

4


SESSION 2 – KESTERITE ABSORBER

OPTIMIZATION

Alain Lafond, IMN

Substitution of Li for Cu

Band-gap from 1.5 - 1.9 eV

Suitable as top cell of tandem solar cells

Insertion of Li could lower the Cu/Zn disorder

Stefan Haaß, Empa

For each alkali metal and concentration separate

adjustment of Sn content mandatory

5

0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5

0.0

0.2

0.4

0.6

0.8

1.0

K/M

(a

rbitra

ry u

nits)

Energy (eV)

x=0

x=0.22

x=0.30

x=0.36

x=0.76

x=1


SESSION 2 – KESTERITE ABSORBER

OPTIMIZATION

Chang Yan, UNSW

By optimizing the CZTS baseline and the ZnCdS

buffer, 9.7 % efficiency pure sulfide CZTS device

(total 0.24 cm2) is achieved in our lab

Yi Ren, Uppsala University

Impact of SnS secondary phases on Cu2ZnSnS4 thin film solar cells:

We observed the SnS phase condensed on CZTS surface is not useful for solar cells

We discovered that the SnS on rear CZTS could be beneficial to the current of solar cells

We discussed SnS can possibly benefit thin solar cells via the passivation effect

6


SESSION 3 – STRUCTURAL PROPERTIES OF KESTERITE ABSORBERS

Jose Marquez, Northumbria University

Study of the importance and influence of the tetragonal distortion (c/2a) on the properties of

CZTSSe absorbers and devices, keep it low!

A simplified approach has been proposed for evaluating the tetragonal distortion that might be

used to correlate:

Metal ratios, ordering level and/or Ge incorporation

Charles Hages, HZB

Interpreting Time Resolved Photoluminescense for Kesterites

PL decay does not follow SRH recombination (Carrier Redistribution / Minority Carrier de-trapping)

Minority Carrier Lifetime is hundreds of picoseconds rather than a few nanoseconds

Common pitfalls in analyzing TRPL data

7


SESSION 3 – STRUCTURAL PROPERTIES OF KESTERITE ABSORBERS

Mikhail Sulimov, Strathclyde University / Ural Federal University

Effects of [Cu]/[Zn+Sn] ratio on optical spectra of Cu2ZnSnSe4 thin films

The changes in the optical spectroscopy parameters along with improvements in the solar cell

performance are consistent with a reduction of the CuZn defect population, rising

concentration of VCu and ZnCu-VCu as well as with increasing ordering of Cu and Zn atoms in

the (001) plane

Elisa Valle-Rios, HZB

Intrinsic point defects in off-stoichiometic

kesterite CZTSe types

8


SESSION 4 – PROGRESS IN HETEROJUNCTION FORMATION

Haibing Xie, IREC

Epitaxial growth of Al(OH)3 nanolayers using a facile wet chemical treatment

Considerable enhancement of VOC, FF and conversion efficiency of CZTSSe solar cells

Best efficiency of 9.1 % (NO ARC) was obtained for a Se-rich CZTSSe solar cell

Tove Ericson, Uppsala University

Zn1-xSnxOy band gap was varied by ALD process temperature

highest VOC for 145 °C

highest FF for 165 °C

both with better efficiency than their CdS reference

Cd-free Cu2ZnSnS4 cell with 9.0 % efficiency (incl. AR)

9


SESSION 4 – PROGRESS IN HETEROJUNCTION FORMATION

Andrea Crovetto, Technical University of Denmark

An epitaxial Cu2ZnSnS4/CeO2 interface can be achieved at 50˚C

Works successfully as a passivation layer

Tends to block current: must be as thin as possible (atomic layer dep.?)

Cannot be a stand-alone buffer layer

This materials search approach could be used for other candidate materials

Leo Choubrac, IMN

CdIn2S4 buffer layer

Collection length & VOC can be as good as CdS

JSC can be improved

10

0%

20%

40%

60%

80%

100%

300 500 700 900 1100 1300

CONFIDENTIAL – INTERNAL USE11


SESSION 5 – PROGRESS IN REAR CONTACT AND SUBSTRATE

Moises Espindola-Rodriguez, IREC

Several functionalized transparent

conductive oxides have been tested as

back contact for Kesterite solar cells:

The most promising metal-oxide are :

MoO3, V2O5 and TiO2 (n-type).

FTO/Mo works better for possible tandem

and bifacial structures.

The back interface still needs to be

optimized

12

Mo

FTO

Glass

i:ZnO/ITO

CdS

CZTSSe

FRONT (ITO)

Abet Class AAA Solar Simulator

AM1.5G

REAR (Glass)

Oriel Class A BB Solar Simulator

AM1.5G

Mo

FTO

Glass

i:ZnO/ITO

CdS

CZTSSe

FRONT (ITO)

Abet Class AAA Solar Simulator

AM1.5G

REAR (Glass)

Oriel Class A BB Solar Simulator

AM1.5G

Si-HIT-Cell


SESSION 5 – PROGRESS IN REAR CONTACT AND SUBSTRATE

Markus Neuschitzer, IREC

It is possible to fabricate CZTSe devices at T < 500ºC on polyimide (eff. = 4.9 %) and on SLG (eff. = 6.4 %)

NaF and KF are effective strategies to dope the CZTSe absorber at low T

Samaneh Ranjbar, imec

Enhancement of

back contact by introducing a MoO3-x

interfacial layer

p-n junction by introducing a TiO2 interfacial layer

13


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7 european kesteriteworkshop overview

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