Advanced Materials Development for Printed Photovoltaic Devices. Prof. Darren Bagnall : APAC Innovation Summit 2016

Transcription

1 Advanced Materials Development for Printed Photovoltaic Devices Prof. Darren Bagnall : APAC Innovation Summit 2016

2 Conclusions Silicon-wafer based solar technologies are set to dominate the photovoltaic industry for the next 10 years (at least) This might include 30% tandem-on-silicon devices Printing technologies have a key role in Si device technology Printing may have increasing role in future Si cell technology - lithography for interdigitated back contact (IBC) devices - lithography for light-management - printing for module assembly? The holy-grail remains cells/modules based on a printed (painted or sprayed) advanced materials known materials probably not good enough there are important niches (building-integrated, consumer electronics)

3 Overview Aiming: to provide an overview of PV technology, consider the role and opportunity of printing within PV technology. Contents: Introduction to the School of Photovoltaic and Renewable Energy Engineering at UNSW The PV industry current trends Photovoltaic Technologies Printing in Si PV technology Printed PV the holy grail OPV/DSSC/Perovskites? Concluding Remarks

4 The School of Photovoltaic and Renewable Energy Faculty of Engineering, UNSW

5 School of Photovoltaic and Renewable Energy Head of School: Professor Darren Bagnall Scientia Professors Martin Green, Stuart Wenham Professors Gavin Conibeer, Allen Barnett, Thorsten Trupke, Evatt Hawkes 20 Associate Professors, Lecturers and Senior Lecturers 47 Fellows and Research staff 24 Professional an Technical staff 100 HDR Students 400 UG, PGCWK

6 History of SPREE 1974 Martin Green established Photovoltaic research at UNSW Electrical Engineering % silicon cell % standard module ARC Centre of Excellence 2006 School formed % silicon cell 2011Move to Tyree Energy Technology Building 2014 Solar Industrial Research Facility opens % 1-sun solar conversion record 2016 Records for CZTS, Quantum Dot, Large area and Perovskite solar cells.

7 Research Themes Advanced Concepts 3G 2G (OPV, Perovskites, CZTZ) Photonics, Plasmonics Materials Commercial Photovoltaics (1G) High-efficiency Si devices Hydrogenation Plating and Contacts Metrology and Varience Distributed Energy Systems and Policy Energy Efficiency Resource modelling Policy

8 Commercial Silicon Photovoltaics 25 Commercialised Technologies Buried Contact Solar Cells Pluto Modules Semiconductor Finger Cells Efficiency, % PERC UNSW PERL Laser Doping 5 Hydrogenation New charge state control techniques for hydrogenation Transforms multi and UMG material into being like single crystal Plating and contacting technologies Copper plating Laser processes for contact formation and localized doping

9 Photovoltaics and Solar Energy Industry Trends

10 The Cost of Solar Energy International Energy Agency 2016

11 The Learning Curve International Technology Roadmap for PV (ITRPV) 2015

12 Balance of Systems Costs Balance-of-Systems cost is now 3 or 4 times the module cost This places a premium on efficiency (cheap 10% probably isn t good enough to replace conventional modules) Important niches includes: - integrated products (on roof tiles, glazing, steel roofs) and systems - consumer electronics

13 Photovoltaic Technologies

14 Three Generations of Photovoltaics First Generation Silicon wafer based solar sells Second Generation thin film silicon CdTe/CdS CIGS DSSC Perovskite CZTS OPV Nanostructured Quantum Dot (M.A. Green, Prog. Photovolt: Res. Appl. 2001; 9: ) Third Generation Tandem Cells Multi-junction Cells Other High-efficiency concepts 3

15 The NREL plot

16 The NREL plot (zoom)

17 Wafer-Silicon based technology

18 Silicon Wafer Processing Two main wafer types Crystalline silicon (C-Si) (high-efficiency) Multicrystalline (mc-si) (less expensive, efficient) Step 1: Obtain good sand Step 2: Refine (SiO 2 + C Si + CO 2 ) Step 3: Prepare silicon bath Step 4: Grow ingot (FZ or CZ.) Step 5: Grind ingot (shaping for wafers) Step 6: Saw wafers (diamond saw) Step 7: Thickness sort Step 8: Lapping and etching Step 9: Sort and test Step 10: Polish Step 11: Qualify Step 12: sell to PV manufacturer.

19 Commercial Devices: Al-BSF 17% black cell (1974) (NASA) 21% Standard screen-printed cell The standard commercial uses no technology or design features not known in the 1970s, apart from the use of silicon nitride antireflection (AR) coatings, first reported in this context in The present standard commercial cell is essentially a black cell with screenprinted contacts, demonstrating similar energy conversion efficiency (17 18%) Martin Green, Philosophical Transactions of the Royal Society A, July 2013

20 UNSW: PERC and PERL cells UNSW PERC PERL Efficiency, % The Passivated Emitter and Rear Contacts (PERC) started to pay more attention to the rear of the cell, most of the rear surface passivated and metal contact reduced The Passivated Emitter, Rear Locally-diffused (PERL) cell was the first cell to reach 25% and held the world record for most of the last 16 years. The PERL cell revisited the front surface with lithographically defined inverted pyramid structure covered with a thin passivating oxide and a double-layer antireflection coating. Martin Green, Philosophical Transactions of the Royal Society A, July 2013

21 Hydrogenated PERC PERC devices are taking an increasing share of new Si production The most modern lines also incorporate hydrogenation technology Careful thermal processing is found to activate hydrogen in the silicon and thereby passivate a range of defects that otherwise degrade devices. The images show Photoluminescence both before and after hydrogenation this process brings commercial cell efficiencies from around 20% to 22% Hydrogentation@unsw led by Prof. Stuart Wenhan (UNSW), PLimaging@UNSW led by Prof. Thorsten Trupke (BTimaging and UNSW)

22 HIT cells HIT (heterojunction with intrinsic layer) cells combine a-si technology and C-Si technology. Unusually these devices start with an n-type substrate, but then surround the C-Si with p and n-type a- Si layers on the top and bottom of the device. These layers provide excellent passivation and low resistances, they ease contact formation and allow large open-circuit voltages, World record 25.6 % efficient devices have been demonstrated

23 Rear Contact or interdigitated back contact cells (IBC) electron-hole pairs generated by light that is absorbed at the front surface can still be collected at the rear of the cell eliminate shading losses altogether an additional benefit is that cells with both contacts on the rear are easier to interconnect Trina Solar recently set new large-area IBC world record at 23.5%

24 Printing Technologies: Metallization Primarily revolve around metallisation screen printing or lithography Silver is a significant ($ volatile) cost within device manufacture ideally would be replaced by copper (electrodeposited best bet) IBC cells required two types of contact on rear surface and this brings new challenges (for screen printing and electroplating) International Technology Roadmap for PV (ITRPV) 2015

25 Printing Technologies: Optical? increasingly improving device performance is likely to require enhanced optical performance and micro- or nano-structured optical layers Nano-photonic surface layers (moth-eye or Mie-scattering) to reduce reflection and/or scatter light Back-reflector structures reflect and scatter (and thereby light-trap) No clear (or affordable solution at present) but nano-imprinting seems best Spinelli and Polman (Mie Scattering - nanoimprint) Bagnall and Boden (plasmonics and biomimetics)

26 CdTe/CdS Solar Cells (First Solar)

27

28 Cadmium Telluride/Cadmium Sulphide Thanks to Frist Solar CdTE/CdS remains a commercial product 102MW solar farm in Nyngen, NSW Both CdTe and CdS have strong tendencies to form suitable stoichiometric layers of p and n-type material as required, across large substrate areas in commercial module production chemical bath deposition is used for the CdS - (not all materials are this helpful!)

29 Printable Technologies

30 1 st Wave : OPV and DSSC When people talk about printable PV they re mainly talking about dye-sensitised solar cells and organic photovoltaics These are genuine low-temperature liquid-based printable (printed) technologies People still hold on to the early promise of these systems At this time neither have the efficiency to compete with silicon OPV also lacks the durability There are however important niche markets

31

32 1 st Wave : OPV and DSSC When people talk about printable PV they re mainly talking about dye-sensitised solar cells and organic photovoltaics These are genuine low-temperature liquid-based printable (printed) technologies People still hold on to the early promise of these systems At this time neither have the efficiency to compete with silicon OPV also lacks the durability There are however important niche markets

33 2 nd wave : nanospheres and microspheres Nanosolar based on Copper Indium Gallium Diselenide nanospheres N th degree have technology based on silicon microspheres Spheres are suspended in a liquid and printed onto plastic substrates Nanosolar's solar cells were verified by NREL to be as efficient 17.1% in 2011 (but efficiencies for production panels were said to be 8-9%) Most micro & nano approaches (including nanowires and quantum dots module efficiencies limit at 10%

34 Nanosolar was a developer of solar power technology. Based in San Jose, CA, Nanosolar developed and briefly commercialized a low-cost printable solar cell manufacturing process. The company started selling thin-film CIGS panels mid-december 2007, and planned to sell them at 99 cents per watt, much below the market at the time. Prices for solar panels made of crystalline silicon declined significantly during the following years, reducing most of Nanosolar's cost advantage. Co-Founder stated that nanosolar "ultimately failed commercially." and that he would not enter this industry again because of slow-development cycle, complex production problems and the impact of cheap Chinese solar power production. [7] Nanosolar ultimately produced less than 50 MW of solar power capacity despite having raised more than $400 million in investment

35 Perovskites

36 3 rd wave : Perovskites

37

38 Perovskite Devices improved from under 4% efficiency in 2010 to 22% in 2016 the organic-inorganic perovskite can be manufactured by wet chemistry (spin-coat or spray) fundamentally cheaper, but still small and degrade quickly Anita Ho-Baillie team

39 30%-40% Efficiencies? A Perovskite-like device in tandem with a silicon cell (unlikely to be lead-halide) To get 30% both device technologies have to be at >20% as independent cells 24.5% Recently announced (UNSW, ANU, ASU, Monash, Sun-Tech, Trina)

40 Conclusions Silicon-wafer based solar technologies are set to dominate the photovoltaic industry for the next 10 years (at least) This might include 30% tandem devices Printing technologies have a key role in Si device technology Printing may have increasing role in future Si cell technology - lithography for interdigitated back contact (IBC) devices - lithography for light-management - printing for module assembly? The holy-grail remains cells/modules based on a printed (or painted) advanced materials Known materials probably not good enough there are important niches (building-integrated, consumer electronics)