Transparent_Electrodes_for_Efficient_Optoelectronics_Public.pdf

Transcript

1. Transparent Electrodes for Efficient Photovoltaics Monica Morales-Masis, Esteban Rucavado, Raphael Monnard, Eiji Kobayashi, Quentin Jeangros, Jeremy Werner, Bjorn Niesen, Mathieu Boccard, Stefaan De Wolf, Aïcha Hessler-Wyser, and Christophe Ballif MRS Fall Meeting – 2017 Boston, US
2. TCO SHJ solar cell Excellent red response Excellent surface passivation (Voc up to 750 mV) Front Transparent Electrode Optimizing Oxides to Enhance Solar Cell Performance
3. TCO SHJ solar cell Excellent red response Excellent surface passivation (Voc up to 750 mV) Front Transparent Electrode Transparent Carrier Selective Contact Optimizing Oxides to Enhance Solar Cell Performance
4. TCO SHJ solar cell Excellent red response Excellent surface passivation (Voc up to 750 mV) Front Transparent Electrode Transparent Carrier Selective Contact Rear Reflector Up to 4 semiconducting oxides Optimizing Oxides to Enhance Solar Cell Performance
5. Optimizing Oxides to Enhance Solar Cell Performance TCO SHJ solar cell Excellent red response Excellent surface passivation (Voc up to 750 mV) Perovskite Top Cell TCO TCO p+ n- Perovskite top cell Excellent blue-Vis response Low subgap absorption Transparent Electrodes Transparent Carrier Selective Contact Up to 6 semiconducting oxides
6. Optimizing Oxides to Enhance Solar Cell Performance SHJ solar cell Excellent red response Excellent surface passivation (Voc up to 750 mV) Perovskite top cell Excellent blue-Vis response Low subgap absorption TCO Recombination Junction Perovskite Top Cell TCO p+ n- Up to 3 semiconducting oxides
7. The Front Transparent Electrode TCO Perovskite Top Cell TCO TCO p+ n- Requirements § High lateral electrical conductivity. § Broadband transmittance § Low contact resistance with the adjacent layers. § Appropriate refractive index and thickness for maximal light in-coupling. § Damage-free deposition (soft-landing and compatible temperature) s = eN e µ e
8. Transparent Electrodes Types of material systems Ref. M. Morales-Masis et al. Adv. Electron. Mater. Vol. 3 (2017)
9. Comparing TCOs for solar cells Ref. M. Morales-Masis et al. Adv. Electron. Mater. Vol. 3 (2017) !"# = % &'( )* +,- = . / 0 12 = ∫ 456..89 1:; ∫ 456..89
10. IWO:H ICO:H IO:H IZO ITO 20 40 60 80 100 120 140 N e = 2 x 1020 cm-3 Hall mobility (cm2/Vs) High mobility TCOs for solar cells Ref. M. Morales-Masis et al. Adv. Electron. Mater. Vol. 3 (2017)
11. High-Mobility Hydrogenated In 2 O 3 (IO:H, ICO:H, IWO:H) In2 O3 (Ce, W) Ar T = RT-60 °C 100-200 W O2 H2 O DC/RF sputtering Fabrication Ref. Koida et al. Sol. Energy Mat. Sol. C. 93 (2009). L. Barraud et al. Sol. Energy Mat. Sol. C. 115 (2013). E. Kobayashi et al. Sol. Energy Mat. Sol. C. 149 (2016) B. Macco et al. J. Appl. Phys. 120 (2016) J. Yu et al, . Sol. Energy Mat. Sol. C. 144 (2016). Other techniques: • Arc-discharge Ion Plating • ALD • PLD + annealing 200 °C in air E. Kobayashi et al. Sol. Energy Mat. Sol. C. 149 (2016) B. Macco et al. J. Appl. Phys. 120 (2016)
12. High-Mobility Hydrogenated In 2 O 3 (IO:H, ICO:H, IWO:H) In2 O3 (Ce, W) Ar T = RT-60 °C 100-200 W O2 H2 O DC/RF sputtering Fabrication 0 10 20 0 10 20 0 10 20 400 600 800 1000 1200 1400 1600 0 10 20 P 0 = 1E-7 mbar as-dep 200 °C air ann Absorptance (%) P 0 = 1.45E-6 mbar as-dep 200 °C air ann P 0 = 2.4E-6 mbar as-dep 200 °C air ann wavelength (nm) P 0 = 7E-6 mbar as-dep 200 °C air ann Characterization N (1020 cm-3) µ (cm2/Vs) s (Scm-1) Rsh (Wsq-1) IO:H (as-dep) 3 50 2400 40 IO:H annealed 1.5 100 >1800 40 Electrical Properties Optical Properties Abs (%) + annealing 200 °C in air Ref. Koida et al. Sol. Energy Mat. Sol. C. 93 (2009). L. Barraud et al. Sol. Energy Mat. Sol. C. 115 (2013). E. Kobayashi et al. Sol. Energy Mat. Sol. C. 149 (2016) M. Morales-Masis et al. IEEE J. Photovoltaics, 5 (2015). J. Yu et al, . Sol. Energy Mat. Sol. C. 144 (2016).
13. Microstructure (solid phase crystallization at T > 150 °C) SEM Top-view Cross-section IWO:H IO:H XRD 2q
14. Microstructure (solid phase crystallization at T > 150 °C) SEM Top-view Cross-section IWO:H IO:H XRD 2q 500 nm µ Hall µ opt µ Hall = µ opt No scattering by grain boundaries µ = et/m* τ = average scattering time (s) FTIR
15. Summary Hydrogenated In 2 O 3 • Excellent optoelectronic properties –High electron mobility (up to 100 cm2/Vs). –High transmittance in the NIR. • H 2 O / H 2 desorption with annealing –High contact resistance with Ag Ref. L. Barraud et al. Sol. Energy Mat. Sol. C. 115 (2013). –H2 degrades the transparency of MoOx. Ref. J. Geissbühler et al., APL, 2015 J. Werner et al. ACS Applied Mat Interfaces 8 (2017). S. Essig et al. Solar RRL 2 (2018) IO:H MoOx Can we Synthesized High-Mobility TCOs Without Intentionally Introducing H 2 O? Amorphous InZnO Zr-doped In2 O3 (IZrO)
16. InO-ZnO (90/10 wt%) Ar T = RT-60 °C 100-200 W O2 DC/RF sputtering Fabrication + annealing 200 °C in air Amorphous InZnO (a-IZO) Ref. M. Morales-Masis et al. IEEE J. Photovoltaics, Vol. 5, 2015
17. InO-ZnO (90/10 wt%) Ar T = RT-60 °C 100-200 W O2 DC/RF sputtering Fabrication + annealing 200 °C in air Amorphous InZnO (a-IZO) Characterization Electrical Properties Optical Properties µ e = 40-60 cm2/Vs No change with annealing Amorphous material (before and after annealing) Low IR transmittance But … Narrow band gap Ref. M. Morales-Masis et al. IEEE J. Photovoltaics, Vol. 5, 2015
18. a-IZO: as front contact in SHJ solar cells 0 100 200 300 400 500 600 700 0 5 10 15 20 25 30 35 40 Current density (mA/cm2) Voltage (mV) Area = 3.96 cm2 V OC = 727 mV J SC = 39.35 mA/cm2 FF = 77.9 % Efficiency = 22.27 % Certified CalLab Ref. M. Morales-Masis et al. IEEE J. Photovoltaics, Vol. 5, 2015 S. Martin de Nicolas, unpublished results.
19. a-IZO: as rear contact in semi-transparent perovskite top cells Ref. J. Werner et al. SolMat, 141, 2015 à IZO: 9.7% à MoOx/IZO: 10.3% IZO Low power- low temp. deposition: no-sputter damage Low Rsh , low NIR absorp.
20. Ne ↑ a-IZO, ITO, IO:H: comparison Amorphous to polycrystalline phase transition. Ref. M. Morales-Masis et al. IEEE J. Photovoltaics, Vol. 5, 2015
21. a-IZO, ITO, IO:H: comparison Can we combine high mobility and high carrier density?
22. Zr-doped In 2 O 3 ultra-transparent and conductive electrode In2 O3 :ZrO2 (98/2 wt%) Ar T = RT-60 °C 100 W O 2 H 2 O DC/RF sputtering Fabrication + annealing 200 °C in air Pbase < 1E-6 mbar N (1020 cm-3) µ (cm2/Vs) s (Scm-1) Rsh (Wsq-1) IZrO (as-dep) 4 x 1020 40 2500 40 IZrO annealed 2-3 x 1020 90-100 4000 25 Characterization Electrical Properties Optical Properties Ref. M. Morales-Masis et al. IEEE J. Photovoltaics, Vol. 8, 1202-1207, 2018
23. 3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 0 1 2 3 4 O 2 (%) as-dep. 200 °C ann. 2.5 5.0 11 22 (a hv)2 (1011 eV 2 cm-2) photon energy (eV) Burstein-Moss shift: Blue shift with increasing N e Zr-doped In 2 O 3 ultra-transparent and conductive electrode Ref. M. Morales-Masis et al. IEEE J. Photovoltaics, Vol. 8, 1202-1207, 2018
24. IZrO, a-IZO, ITO, IO:H: comparison 3.0 3.5 4.0 4.5 0 1 2 3 4 (a hv)2 (x1011 eV2 cm-2) hv (eV) In 2 O 3 :Sn (ITO) - 200 °C ann In 2 O 3 :H (IO:H) - 200 °C ann In 2 O 3 :Zr (IZrO) - 200 °C ann InZnO (IZO) - 200 °C ann Optimized Properties In2 O3 :Zr (IZrO) In2 O3 :H (IOH) In2 O3 :Sn (ITO) N (cm-3) 2.5×1020 1×1020 2×1020 m (cm2/Vs) 100 110 30 Rsheet for 100 nm (W/□) 25 50 100 Ref. M. Morales-Masis et al. IEEE J. Photovoltaics, Vol. 8, 1202-1207, 2018
25. Cell ( ( ( ( IZrO: as front contact in SHJ solar cells ITO 2E-04 W cm2 In2 O3 :Zr < 1E-04 W cm2 TLM ITO >100 W/sq In2 O3 :Zr 30 W/sq (80 nm) 60 W/sq (40 nm) Rsh Cell FF(%) Voc (mV) Jsc (mA/cm2) h (%) IZrO (50nm + MgF2) 76.7 714.5 40.6 22.3 IZrO (100nm) 77.1 715.6 40.3 22.2 Ref ITO 77.7 714.3 40.1 22.3 SEM top view : Quentin Jeangros and Federica Landucci.
26. Zr-doped In 2 O 3 as front contact in SHJ cells Optimized Properties In2 O3 :Zr (IO:Zr) In2 O3 :H (IO:H) In2 O3 :Sn (ITO) N (cm-3) 2.5×1020 1×1020 2×1020 µ (cm2/Vs) 100 110 30 Rsheet for 100 nm (W/□) 25 50 100 Contact resistance with Ag (Ohm.cm2) < 1.10-4 > 1.10-4 (depends on water content) [3] < 1.10-4 Voc (mV) 725 (727) 726 (727) 724 (727) FF (%) 79.4 (80.5) 80.6 (81.0) 80.3 (81.5) Jsc (mA/cm2) 40.0 (40.2) 39.7 (39.9) 39.5 (39.7) Efficiency (%) 23.0 (23.4) 23.2 (23.4) 23.0 (23.4) 2E20 cm-3 IO:Zr Ref. M. Morales-Masis et al. IEEE J. Photovoltaics, Vol. 8, 1202-1207, 2018
27. Zr-doped In 2 O 3 as front contact in SHJ cells Ref. M. Morales-Masis et al. IEEE J. Photovoltaics, Vol. 8, 1202-1207, 2018
28. Summary Zr:In2 O3 •Excellent optoelectronic properties –High electron mobility (up to 100 cm2/Vs). –Broadband transmittance– optically ideal for tandem cells. •Low H2 content (~ 2 at% H2 - RBS) –Low contact resistance with Ag –Good partner for new (H2 –sensitive) oxide selective contacts. • Low FF in SJH cells (optimization required for high efficiency) TCO
29. Optimizing Oxides to Enhance Solar Cell Performance TCO Recombination Junction Perovskite Top Cell TCO p+ n-
30. High-temperature stable ZnSnO Recombination junction in c-Si / mesoscopic perovskite tandems cells One of the Challenges: Mesoscopic perovskite top cell typically requires a 500 °C annealing step. • SHJ: not compatible for T > 300 °C. • Std TCOs degrade at 500 °C. Solution: • high T stable Si cells • high T intermediate recombination layer ITO/IO:H MoOx Spiro-OMeTAD CH3 NH3 PbI3 m-TiO2 c-TiO2 ZTO P-doped diffused layer N-doped Si wafer BSF SiO2 Al Zinc tin oxide (ZTO) Ref. J. Werner et al. APL 109, 2016
31. RMS = 1.2 nm µ = 12 cm2/Vs Ne = 5 x 1019 cm-3 µ = 21 cm2/Vs Ne = 7.3 x 1019 cm-3 100 nm HAADF ZnSnO Glass substrate Amorphous Zn-Sn-O from combinatorial growth to application in flexible OLEDs and high- temperature processing devices Ref. M. Morales-Masis, et al. Adv. Funct. Mater. 26 (2016) J. Werner et al. APL 109, 2016 E. Rucavado et al. Phys. Rev. B. 95, 245204 (2017) ZTO ZnSnO RBS: Sn/Zn = 4.2
32. RMS = 1.2 nm µ = 12 cm2/Vs Ne = 5 x 1019 cm-3 µ = 21 cm2/Vs Ne = 7.3 x 1019 cm-3 100 nm HAADF ZnSnO Glass substrate Amorphous Zn-Sn-O from combinatorial growth to application in flexible OLEDs and high- temperature processing devices Ref. M. Morales-Masis, et al. Adv. Funct. Mater. 26 (2016) J. Werner et al. APL 109, 2016 E. Rucavado et al. Phys. Rev. B. 95, 245204 (2017) ZnSnO RBS: Sn/Zn = 4.2 What is the effect of high-temperature post-deposition treatments?
33. a-ZTO: sub-band absorption and nature of sub-band defects Optical properties Electrical properties air N2 H2 as-dep 500 °C ann 500 °C ann as-dep µ = 21 cm2 V-1s-1 Ne = 7 E 19 cm-3 s = 245 S cm-1 Annealing in air, r(O2 ) ↑ ↑ µ = 35 cm2 V-1s-1 N e = 6 E 19 cm-3 s = 336 S cm-1 Annealing in H2 , r(O2 ) ↑ ↑ µ = 24 cm2 V-1s-1 N e = 1.6 E 20 cm-3 s = 615 S cm-1 500 °C ann as-dep DFT calculations Density of states (DOS) energy (eV) Conducti on band Valence band Conduction band Sn-Sn pairs Uncoord. Ox. Photon energy (eV) X r(O2 ) ↑ Collaboration with Prof. C. Elsasser and Dr. D. Urban @ Fraunhofer IWM Ref. E. Rucavado et al. Phys. Rev. B. 95, 245204 (2017)
34. a-ZTO: sub-band absorption and nature of sub-band defects Optical properties Electrical properties air N2 H2 as-dep 500 °C ann 500 °C ann as-dep µ = 21 cm2 V-1s-1 Ne = 7 E 19 cm-3 s = 245 S cm-1 Annealing in air, r(O2 ) ↑ ↑ µ = 35 cm2 V-1s-1 N e = 6 E 19 cm-3 s = 336 S cm-1 Annealing in H2 , r(O2 ) ↑ µ = 24 cm2 V-1s-1 N e = 1.6 E 20 cm-3 s = 615 S cm-1 500 °C ann as-dep DFT calculations Density of states (DOS) energy (eV) Conducti on band Valence band Conduction band Sn-Sn pairs Uncoord. Ox. Photon energy (eV) Ref. E. Rucavado et al. Phys. Rev. B. 95, 245204 (2017) Collaboration with Prof. C. Elsasser and Dr. D. Urban @ Fraunhofer IWM
35. High-temperature stable ZnSnO Recombination junction in c-Si / mesoscopic perovskite tandems cells ITO/IO:H MoOx Spiro-OMeTAD CH 3 NH 3 PbI 3 m-TiO 2 c-TiO 2 ZTO P-doped diffused layer N-doped Si wafer BSF SiO2 Al Ref. J. Werner, E. Rucavado, De Wolf, M. Morales-Masis, B. Niesen, C. Ballif et al. APL 109, 2016
36. Combinatorial growth to tune optical properties of TCOs Rear emitter application Ref. A. Dabirian, De Wolf, M. Morales-Masis, B. Niesen, C. Ballif et al. Adv. Mater. Interfaces 3 (2016)
37. Soft-deposition techniques Amorphous GaOx grown by low-temperature PECVD Advantages of PECVD: • High deposition rate • Deposition over large areas • Industrially widespread Gas system rf generator electrode electrode substrate heater Pump system reaction chamber plasma Ref. E. Kobayashi et. al. J. Vacuum Science and Technology A, 36 (2018)
38. Fabrication Amorphous GaOx grown by low-temperature PECVD Characterization Optical Properties High transmittance Wide band gap • PECVD , 70 MHz • Precursors: TMG (Ga(CH 3 ) 3 ) CO 2 • Flow ratios: Q = ,-. /01 2345 ,-. /01 23456789 /01 2345 • T = 200 °C Ref. E. Kobayashi et. al. J. Vacuum Science and Technology A, 36 (2018)
39. Fabrication Amorphous GaOx grown by low-temperature PECVD Characterization Optical Properties Low refractive index • PECVD , 70 MHz • Precursors: TMG (Ga(CH 3 ) 3 ) CO 2 • Flow ratios: Q = ,-. /01 2345 ,-. /01 23456789 /01 2345 • T = 200 °C Ref. E. Kobayashi et. al. J. Vacuum Science and Technology A, 36 (2018)
40. Conclusions •High mobility important for IR transparency •Combining high-mobility and high-carrier density: ultra-transparent electrode •Making a perfect transparent electrode is not all •Co-sputtering deposition is an ideal tool to discover new compounds and fine-tuned refractive index of materials •Oxides by PECVD: alternative soft deposition techniques.
41. Thank you for your attention! Acknowledgements PVLab members and collaborators at: KAUST UC Berkeley - LBNL Fraunhofer IWM CHOSHU INDUSTRY CO., LTD. AIST From May 2018 @ m.moralesmasis@utwente.nl