High Quality Metallic Grid Preparation on Transparent Conductive Oxide (TCO) Coated Substrates

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1 High Quality Metallic Grid Preparation on Transparent Conductive Oxide (TCO) Coated Substrates Larissa Grinis and Arie Zaban Institute of Nanotechnology & Advanced Materials, Bar- Ilan University Ramat Gan, Israel

2 The Challenge High sheet resistance of TCOcoated substrates leads to: non-homogenous current distribution over substrates and results in nonhomogenous emission Metal grids produced by screen-printing or ink-printing are: porous, possess high specific resistance; notable for relatively poor adhesion to TCO

3 The requirement Good electrical contact to TCO High conductivity Strong adhesion to TCO The process of metal deposition should be consistent with poor ITO stability in highly acidic and basic environments low cost / Scale up Roll-to-Roll technology for flexible substrates

4 The Solution A new electrochemical method For the Deposition of metals and alloys Silver, copper, nickel on TCO- coated glass and plastic ITO- glass, ITO- PET, FTO-glass With Ultra high adhesion Variable thickness Dense metal structure

5 Analysis of deposited layers by Focused Ion Beam (FIB) Insulating Insulating coating coating Metal/Alloy Metal/Alloy TCO Plastic

6 deposition on ITO-glass 10 Ohm/sq (FIB image) Cross-section Cross - section ITO Glass The layer thickness here is 2 mkm. layer is dense, strongly adherent to ITO/glass, possesses excellent electrical contact to ITO and excellent conductivity.

7 deposition on ITO glass 10 Ohm/sq (FIB image) Glass Cross-section ITO The layer thickness here is 3 mkm. layer is dense, strongly adherent to ITO/glass, possesses excellent electrical contact to ITO and excellent conductivity.

8 deposition on ITO-glass 10 Ohm/sq (HRSEM image) Top view

9 deposition on FTO - glass 15 Ohm/sq (FIB image) Glass Cross-section FTO The layer thickness here is 2.8 mkm. layer is dense, strongly adherent to FTO/glass, possesses excellent electrical contact to FTO and excellent conductivity

10 deposition on FTO-glass 15 Ohm/sq (FIB images) FTO FTO Cross-section FTO FTO

11 deposition on ITO/PET 45 Ohm/sq (FIB images) Cross - section Cross - section PET ITO PET ITO Cross-section Cross -- section Top-view Top-view PET ITO

12 Cu deposition on ITO glass 10 Ohm/sq (FIB image) Glass Cross - section Cu ITO The Cu layer thickness here is 1.7 mkm. Cu layer is dense, strongly adherent to ITO/glass, possesses excellent electrical contact to ITO and excellent conductivity.

13 Cu deposition on FTO glass 15 Ohm/sq (FIB images) Cross-section Cu Cu FTO Glass The Cu layer thickness here is 2.18 mkm. Cu layer is dense, strongly adherent to FTO/glass, possesses excellent electrical contact to FTO and excellent conductivity.

14 Cu deposition on FTO glass 15 Ohm/sq (FIB images) Top view Cu

15 Cu deposition on ITO-PET 45 Ohm/sq (FIB images) Cross - section Cu ITO PET The Cu layer thickness here is 2.6 mkm. Cu layer is dense, strongly adherent to ITO/PET, possesses excellent electrical contact to ITO and excellent conductivity.

16 Cu deposition on ITO-PET 45 Ohm/sq (FIB images) Cu Top view

17 Ni-Co alloy deposition on ITO/PET 45 Ohm/sq (FIB image) The Ni-Co alloy thickness here is 6 mkm. Ni-Co layer is dense, strongly adherent to ITO/PET, possesses excellent electrical contact to ITO and excellent conductivity Cross-section - section Ni-Co Top-view ITO Ni-Co Ni-Co PET

18 Consecutive metallic layers on ITO-PET (FIB image) Two or more consecutive metallic layers can be deposited on TCO. Here, for example, crosssection of the sample with two consecutive layers on ITO/PET is shown : first layer is (539 nm), second layer is Ni-Co alloy (2mkm) Ni-Co ITOO PET

19 Conformal Insulating Coating on top of metallic layer Me x O y Based on sol-gel electrophoretic deposition we developed insulating coating of the metallic grid to avoid electric shorts. PEN ITO Me x O y Me x O y ITO PEN PEN Ni-Co

20 Conformal Insulating Coating on top of metallic layer Me x O y Me x O y PET ITO PET ITO Cross-section Me x O y Me x O y Cu Cu PET ITO PET ITO

21 The metallic grid preparation procedure Optional as insulator or 2 nd metal Metal/Alloy TCO Preparation of a patterned mask Electrochemical deposition Optional- conformal insulating metal oxide or 2 nd metal coating Glass or Plastic

22 Silver metallic grids on ITO-PET 45 Ohm/sq

23 Copper metallic grids on ITO-PET 45 Ohm/sq

24 Ni-Co metallic grids on ITO-PET 45 Ohm/sq

25 Ni-Co metallic grid on FTO-glass Anode for Dye Sensitized Solar Cell. (Blue) mesoporous TiO 2

26 Effect of metallic grids on conductivity of TCO-coated substrates The sheet resistance of TCO-coated glass and plastic substrates with and without metallic grids has been measured using 4 point probe measurements. The sheet resistance was found up to 50 times lower when substrates were prepared with embedded metallic grids. As a model, dye sensitized solar cells (DSSC) have been prepared on ITO-PET (45 Ohm/sq) plastic substrates with and without Ni-Co alloy metallic grids.

27 Effect of metallic grids on conductivity of TCO-coated substrates Current density, ma/cm Pmax Voc Jsc F.F. Eff mkw mv ma/cm 2 % % Voltage, mv 1 The cells aperture area was 8.5 cm 2 The obtained results of photovoltaic measurements under 1 sun (AM 1.5) illumination are shown on the graph and in the table.

28 Prepared DSSC with Ni-Co alloy grid on ITO-PET

29 Conclusions We have developed a new electrochemical method to deposit different metals and alloys on TCO-coated glass and plastic substrates with a very strong adhesion and good electrical contact to TCO. The thickness of metallic layers can reach a few microns without deterioration of the adhesion to TCO. The deposited metals and alloys have a dense structure and good electrical conductivity. We further developed insulating metal oxide coating of deposited metallic grids by sol-gel electrophoretic deposition in order to avoid electrical shorts.

30 Conclusions The developed method can be applied for the fabrication of high quality metallic grid-embedded TCO-coated glass and plastic substrates in order to substantially diminish the resistive losses of conductive glass and plastic substrates.

31 Thank you!