Thin-film Silicon Photovoltaics Miro Zeman

Transcription

1 Thin-film Silicon Photovoltaics Miro Zeman Delft University of Technology, Photovoltaic Materials and Devices group

2 Outline 1. Introduction 2. Cost and performance 3. Key challenge: Increasing efficiency New materials Light trapping Nano-imprint lithography Modeling New concepts 4. Summary and outlook

3 LATEST ACHIEVEMENTS

4 Record thin-film Si solar cell: Stabilized efficiency LG Electronics record solar cell Triple junction: a-si/μc-si/μc-si) Courtesy of Dr. Heon-Min Lee, LG Electronics Advanced Research Institute

5 1 INTRODUCTION

6 Message Matured low-cost technology with potential for further cost reduction Suitable for very large-scale (TW) implementation Sunbelt regions, BIPV Global research effort to enhance the performance Focus: Light management, thin design, new materials and concepts All PV technologies can benefit from the achievements

7 2 COST AND PERFORMANCE

8 Oerlikon Solar THINFAB TM 140 production line Some unique features: Lowest module manufacturing cost: 0.35/Wp enabling electricity production at 0.07/kWh Guaranteed performance: 10.8% module efficiency, >97% fab yield, 140 MW fab output Fastest module energy payback time: less than 1 year Clean module design: no toxic elements and lowest CO 2 footprint of 21g CO 2 /kwh Source: OERLIKON SOLAR (

9 Competitive performance of micromorph modules Oerlikon Solar outdoor test facility (Arizona/USA) Courtesy of Dr.Juergen Sutterluetti and Dr.Stefan Sellner OERLIKON SOLAR

10 Competitive performance of micromorph modules c-si (class A): P nom : 220 Wp with Cum. Energy Yield [kwh/kwp] = 3336 kwh Micromorph: P nom : 125 Wp with Cum. Energy Yield [kwh/kwp] = 3450 kwh (+3.4%) Courtesy of Dr.Juergen Sutterluetti and Dr.Stefan Sellner OERLIKON SOLAR

11 HyET Solar flexible modules Unique product and technology A flexible and lightweight PV product for application on lightly constructed rooftops with a very large world wide market Product passed the IEC certification tests successfully Broad technology based on roll-to-roll deposition steps, wet chemical steps as well as lamination steps Courtesy of Dr. Edward Hamers, HyET Solar

12 3 KEY CHALLENGE: Increasing efficiency

13 State-of-the-art Modules: Best thin-film Si R&D modules: 11-12% Commercial modules 6-10% (total area efficiency) Best thin c-si on glass mini-module 10.4% (CSG Solar) Solar cells: Best thin-film Si solar cells: η in = 16.3% (USSC triple-junction solar cell) η st = 13.4% (LG Electronics triple-junction solar cell) Challenge: Stabilized efficiency of thin-film Si solar cells > 20 %

14 Increasing efficiency Delicate interplay: Material and interface processing Defect engineering (V oc, FF) Spectral utilization Multi-junction concept Intermediate reflectors (η) Light trapping Rough interfaces Back reflector, TCO (J sc ) International research effort to increase the efficiency

15 Thin-film Si solar cell structures: superstrate configuration Single-junction Double-junction Triple-junction Glass plate Glass plate Glass plate TCO TCO TCO a-si:h μc-si:h a-si:h a-si:h a-sige:h μc-si:h a-si:h a-sige:h/μc-si:h a-sige:h/μc-si:h TCO Metal η st =10.1% (a-si) Oerlikon η in =10.9% (μc-si) EPFL-IMT TCO Metal η st =12.3% (a-si/ μc-si) Kaneka η st =12.3% (a-si/ μc-si) Oerlikon* TCO Metal η st = 13.4% (a-si/μc-si/μc-si) LGE

16 Thin crystalline Si solar cell on glass Glass plate Intermediate layer p-type Crystalline silicon (total thickness 5-10 μm) Metal n + -type resist Metal η=4.7% (EBC 10 μm pc-si) HZB η=8.4% (LC 10 μm pc-si) UNSW+Suntech Si deposition process: 1. Crystallization of a-si films Deposition of a-si (PE-CVD) Crystallization of a-si layers (Solid phase crystallization) 2. Crystallization of Si films Deposition of Si (e-beam evaporation or sputtering at elevated temperatures) Crystallization of Si layers (Line-shaped e-beam and laser crystallization)

17 3.1 IMPROVING EFFICIENCY: New materials

18 New materials: Amorphous and microcrystalline Si alloys Application in tandem a-si/μc-si solar cell ZnO Back contact n- SiO X µc-si:h (1.1μm) p- SiO X n- SiO X a-si:h ZnO Front contact 250 nm p-sio x Glass 1 μm M. Despeisse et al,, Physica Status Solidi A, 208 (8), (EPFL-IMT)

19 3.2 IMPROVING EFFICIENCY : Light trapping

20 Light trapping: Scattering at rough interfaces Flat surface Randomly-textured surface Modulated surface texture Modulated multisurface texture Glass Glass Glass Glass TCO TCO TCO TCO Si Si Si Si TCO TCO TCO Metal Metal Metal Metal multi-step processes in TCO deposition multi-surface approach

21 Light trapping: Scattering at rough interfaces Modulated surface-textured substrates σ RMS = 221 nm σ RMS = 297 nm Tokyo Institute of Technology Delft University of Technology A. Hongsingthong et al., Applied Physics Express 3 (2010) (Tokyo Tech) O. Isabella, J. Krč, and M. Zeman, Applied Physics Letters 97, (2010). (TU Delft)

22 Light trapping: Modulated surface textures Manipulation of scattering level EG1 σ RMS = 297 nm EG3 σ RMS = 630 nm H T EG5 σ RMS = 742 nm Flat glass / AZOR (ref.) EG1-based substrates EG2 / AZOR EG3 / AZOR EG4 / AZOR EG5 / AZOR EG1 / AZOR EG1 (offset) Wavelength [nm] O. Isabella, P. Liu, B. Bolman, J. Krc, M. Zeman, Mater. Res. Soc. Symp. Proc. Vol. 1321, (TU Delft)

23 Light trapping: Modulated surface textures Improved AR and scattering 1.0 Single-junction a-si solar cells J ph = +8.46% EQE μm Flat glass / AZOR (1.2 m) EG5 / AZOR (1.2 m) Wavelength [nm] O. Isabella, P. Liu, B. Bolman, J. Krc, M. Zeman, Mater. Res. Soc. Symp. Proc. Vol. 1321, (TU Delft)

24 3.3 IMPROVING EFFICIENCY : Nano-imprint lithography

25 Light trapping: Scattering and diffraction Nano-imprint lithography Any rough morphology possible with high-fidelity Periodic surface textures (1-D and 2-D diffraction gratings) Decoupling optical and electrical properties of electrodes Thin TCO layers (suppressing parasitic absorption) New concepts (3-D solar cells, plasmonics, nano-antenas) Texture A stamp PDMS Nano-imprinting stamp Texture A Master Master Replica Replica

26 Light trapping: Scattering at rough interfaces Nano-imprint + new TCO layer (In 2 O 3 :H (IOH)*) Master ZnO back Replica incoming light incoming light mc-si:h interlayer a-si:h ZnO front ZnO back mc-si:h interlayer a-si:h In 2 O 3 :H NIL resin C. Battaglia et al., Nano Letters 11, , (EPFL-IMT) *T. Koida, H. Fujiwara, and M. Kondo, Japanese Journal of Applied Physics,46(28), L685, (AIST)

27 Light trapping: Scattering at rough interfaces Nano-imprint + new TCO layer Flat Substrate J top sc ZnO back [ma/cm 2 ] mc-si:h J bottom sc [ma/cm 2 ] V oc [mv] FF Eff [%] [%] Master a-si:h Replica+ITO In 2 O 3 :H glass Replica+InO:H Flat+InO:H ma/cm 2 with 250nm a-si, 30nm IRL, 1.1 μm μc-si No AR coating. C. Battaglia et al., Nano Letters 11, , (EPFL-IMT) Ch. Ballif et al., PV-IEEE, (EPFL-IMT)

28 Light trapping: Periodic diffraction gratings Angle-selective manipulation of light scattered at the rough interfaces using 1-D and 2-D diffraction gratings Grating structures fabricated by OM&T, Moser Baer

29 Light trapping: Random versus periodic texture Glass Glass TCO TCO Si TCO Metal Si TCO Metal Absorption enhancement: Random texture 4 n 2 Periodic (square) texture π 4 n 2 Periodic (triangular) texture 2π/ 3 4 n 2 (thick film, single wavelength) Yablonovitch et al., JOSA, Z. Yu, A. Raman and S. Fan, Optical Express, (Stanford University) F.-J. Haug, K. Söderström, A. Naqavi, and C. Ballif, J. Appl. Physics 109, , (EPFL-IMT)

30 3.4 IMPROVING EFFICIENCY: Modeling

31 3-D optical modeling: Single-junction solar cell Optimization of 2-D gratings and evaluation of absorption losses Absorptance and optical losses D grating: P 1 = 600 nm, P 2 = 600 nm, h = 300 nm 2-D ma/cm 2 1-D ma/cm 2 Flat ma/cm Wavelength [nm] R Front ZnO:Al p n Back ZnO Ag i - 2-D gratings i - 1-D gratings Flat O. Isabella, S. Solntsev, D. Caratelli and M. Zeman, Progress in Photovoltaics, (TU Delft)

32 3-D optical modeling: Triple-junction Si solar cell Optimization of 2-D gratings and intermediate and back reflectors ma/cm 2 IOH (125 nm) IR1 (30 nm) IR2 (80 nm) i bottom nc-si (2800 nm) i top (175 nm) i middle (175 nm) Absorptance [-] ma/cm ma/cm 2 Schockley-Queisser limit ma/cm 2 ( nm) ma/cm 2 BAZO (70 nm) Ag (100 nm) Target: J Ph-tot = 30 ma/cm 2 η= 17% No light trapping (2 passes) Tjedje-Yablonovitch limit Deckman-Wronski limit nc-si:h on 2-D gratings Wavelength [nm] O. Isabella, M. El-Shinawy, S. Solntsev, M. Zeman, OSA conference, Eindhoven, (TU Delft)

33 3.5 IMPROVING EFFICIENCY: New concepts

34 Plasmonics Localized surface plasmon resonance in Ag NPs Resonance wavelength can be tuned to NIR R. Santbergen et al., Journal of Optics 14, , 2012 (TU Delft) C. Eminian et al., Prog. Photovolt., 19, 260, 2011 (EPFL-IMT) E. Moulin et al., Thin Solid Films, 516, 6813, 2008 (FZ Julich)

35 Plasmonics ITO a-si:h/µc-si:h Textured BR σ RMS =40nm Plasmonic BR σ RMS =22nm Ag NPs BR ZnO:Al Ag Glass Broadband high haze factor Smooth surface for high-quality film growth H. Tan, R. Santbergen, A.H.M. Smets, M. Zeman, Nano Letters 12, 4070, (TU Delft)

36 Plasmonics Comparable to state-of-the-art surface-textured substrate Strong scattering without introducing high surface roughness No degradation of V oc and FF compared to a-si flat cell H. Tan, R. Santbergen, A.H.M. Smets, M. Zeman, Nano Letters 12, 4070, (TU Delft) H. Tan, R. Santbergen, G. Tao, A.H.M. Smets, M. Zeman, IEEE-JPV, (TU Delft)

37 Flattened Light-Scattering Substrate (FLiSS) Flat FIG. 1. Concept of the FLiSS for thin-film solar cells. 2-D photonic crystal with flat surface High-quality Si active layer (high V oc and FF) Light trapping in the IR region (high J sc ) H. Sai et al., Applied Physics Letters 98, , 2011.

38 Flattened Light-Scattering Substrate (FLiSS) FIG. 5. J-V curves and corresponding J-V parameters of the μc-si:h cells (1 μm thick) fabricated on a flat substrate, a reference textured substrate, a 2D ZnO grating and a FLiSS. H. Sai et al., Applied Physics Letters 98, , 2011.

39 FLiSS substrate optimization nm inverted pyramid Absorptances and reflectance [-] Total J ph = ma/cm 2 R (9.45 ma/cm 2 ) Front IOH (3.43 ma/cm 2 ) p + n (1.17 ma/cm 2 ) ZnO:Ga (type a) (1.44 ma/cm 2 ) Dead (n) a-si:h (2.19 ma/cm 2 ) Ag (1.08 ma/cm 2 ) i-layer (27.43 ma/cm 2 ) 1 μm μc-si:h 2000 nm Wavelength [nm] O. Isabella, H. Sai, M. Kondo and M. Zeman, IEEE-JPV, 2012

40 Thin crystalline Si on glass: new concepts E-beam crystallized Si material: Nanostructuring process: Nanosphere lithography (NSL) Reactive ion etching (RIE) Si nanowires High light absorption, new concepts for cell structures S. Schmitt et al., Nano Letters, (Cooperation Max-Planck-Institut Erlangen and Helmholtz Zentrum Berlin)

41 SUMMARY and OUTLOOK

42 Summary Performance (η>20%): Increase V oc (growth on textured substrates) Si quantum dot New materials: Absorber materials stable against LID Si based alloys with O, C, and Ge Light management: Low absorption TCOs and ARC 2-D or 3-D PC based flat substrates Novel 2-D or 3-D solar cell structures New ideas and concepts are welcome Si nanowires 100 nm S. Perraud et al., PSS-C, 2012 (Snapsun project) S. Schmitt et al., Nano Letters, (Cooperation Max-Planck-Institut Erlangen and Helmholtz Zentrum Berlin)

43 FP7 Project Fast Track 20 participants 10 research partners 10 industry partners Duration: March 1 st Febr. 28 th 2015 Contribution: EU Aims: Redesign TFSi solar cells, Up-scaling of nano-imprinted substrates Bringing this next-generation technology towards the market with 12% module efficiency Development of a low-cost large-area deposition technology see Poster 3DV.1.45 Courtesy of Dr. Aad Gordijn, (FZ Jülich)

44 Future research outlook Solar cell structure: Thin-film Si based multi-junction cells J ph ( nm)=43.2 ma/cm 2 EQE=0.70 V oc /E gap =0.55 FF=0.75 η 3stack = 18.3% η 4stack = 21.2% Glass plate Front contact Top cell (E gap =1.95eV) a-si, a-sic, a-sio Top middle cell (E gap =1.47eV) a-sige:h Bottom middle cell (E gap =1.12eV) nc-si Bottom cell (E gap =0.75eV) nc-sige Back contact

45 Future research outlook Solar cell structures: Single-junction c-si film solar cell J ph ( nm)=43.2 ma/cm 2 EQE=0.80 V oc /E gap =0.65 FF=0.80 η 1stack = 21.0% Glass plate Intermediate layer Crystalline silicon (total thickness 5-10 μm) Metal Si resist Metal

46 Thank you for your attention!