Solar cell technologies present and future

Transcription

1 Solar cell technologies present and future Joachim LUTHER, Armin ABERLE and Peter Wuerfel Solar Energy Research Institute of Singapore (SERIS) Nature Photonics Technology Conference, Tokyo, Japan 20 October

2 Outline Main market technologies (PV cells) Status of photovoltaics (market and prices) Benchmarks for PV technologies 2010 Routes for performance enhancement of today's market technologies Principles of PV energy conversion compass for navigation Concluding remarks 2

3 Market shares of PV technologies 2009 Total PV market in % 82% Thin films Si Wafers Thin film PV market in % 4% 15% 4% CdTe ClGS a-si micromorph-si 3

4 Silicon wafer photovoltaics Status 2010 Production of silicon wafer PV is growing rapidly (> 30 % p.a.) Proven technical lifetime of > 20 years Module efficiencies 13-20% Applications: All market segments, in particular those with limited space availability (high efficiency required) 4

5 Thin-film photovoltaics Status 2010 Thin-film PV production is growing rapidly (> 30% p.a.) Module efficiencies 4-13 % Semiconductor material consumption reduced about 100 times compared to Si wafer PV Warranted technical lifetime of 20 years Main applications: Green-field power plants, BIPV 5

6 Concentrating photovoltaics, examples Concentrix Amonix SolFocus Emcore 6

7 Multi-junction solar cell, for concentrating and space applications Spectral power density [W/m 2 applem] Wavelength [nm] 7

8 Plastic photovoltaics Source: Konarka 8

9 Outline Main market technologies (PV cells) Status of photovoltaics (market and prices) Benchmarks for PV technologies 2010 Routes for performance enhancement of today's market technologies Principles of PV energy conversion compass for navigation Concluding remarks 9

10 Status of Photovoltaics 2009 Cumulative PV capacity globally installed 22 GW p PV fraction of global electricity generation 0.1 % PV fraction of German electricity generation 1.0 % PV power installed in GW p CAGR* (%) since 2000 ~ 40% Global market volume, 2009 US$ 25 billion *CAGR Compounded annual growth rate Source: SERIS market research

11 PV installations, annual market MW p 18,000 16,000 14,000 12,000 10,000 8,000 6,000 4,000 2,000 0 Rest of World China Japan USA Rest of EU Germany e Manufacturing capacity 2010: 24 GW Si wafer + 7 GW thin-film Source: European Photovoltaic Industry Association (EPIA) 11

12 Price experience (learning) curve, silicon-wafer based modules 10 Euro/ W p September Cumulative Power MW p Source: Solar Generation, IEA-PVPS 2006; SERIS market research

13 Outline Main market technologies (PV cells) Status of photovoltaics (market and prices) Benchmarks for PV technologies 2010 Routes for performance enhancement of today's market technologies Principles of PV energy conversion compass for navigation Concluding remarks 13

14 Benchmarks for PV 2010, bulk power technologies Module efficiency > 10% Technical lifetime of modules 25 years Module prices /W p Solar electricity cost 20 cents/kwh (at solar input kwh m -2 a -1 ) 14

15 Non-bulk power technologies, requirements, examples Building-integrated PV excellent esthetics semi-transparent Small power applications flexible compatibility with other materials 15

16 Outline Main market technologies (PV cells) Status of photovoltaics (market and prices) Benchmarks for PV technologies 2010 Routes for performance enhancement of today's market technologies Principles of PV energy conversion compass for navigation Concluding remarks 16

17 Cost reduction in solar electricity 17

18 Silicon wafer technologies, routes to higher efficiency, examples selective emitters all-back-contact cells n-type silicon better light trapping better surface passivation hetero-junction cells 18

19 Thin-film technologies, routes to higher efficiency, examples Improved light trapping (textured TCOs, textured glass, ) Improved TCOs (less parasitic absorption, better conductivity) Improved semiconductor material quality (lower contamination levels, improved doping control) Tandem solar cells 19

20 Less material consumption in PV, examples Thin-film technologies CdTe Silicon ClGS III-V, plastic, dye Ultra-thin wafers transfer technology (ion implantation for separation) 20

21 Routes to optimised manufacture, examples Wafer technologies in-line technologies in-line process analysis new schemes for contacting, passivation, module assembly, Thin-film technologies optimisation of layer deposition improve TCOs, light trapping, interconnection, encapsulation, General remark: Integrated production today favourable 21

22 Outline Main market technologies (PV cells) Status of photovoltaics (market and prices) Benchmarks for PV technologies 2010 Routes for performance enhancement of today's market technologies Principles of PV energy conversion compass for navigation Concluding remarks 22

23 Thermodynamic analysis, photovoltaic energy conversion applee Exergie E in E out S in Converter S out apples apple appleq T amb applee Exergie = ( E in - E out ) - T amb ( S in - S out ) 23

24 Thermodynamic limits, photovoltaic energy conversion 100% 80% efficiency 60% 40% 20% T s = 5777 K 0% optical concentration T c = 300 K Source: R. Sizmann

25 (Semiconductor) solar cells, ideal transport of energetically excited charge carriers Avoiding irreversibility during transport of e and h, quasi Fermi levels approximately constant Semi-permeable membranes for selectivity of transport 25

26 (Semiconductor) solar cells, chemical potential and cell voltage, achieving entropy balance Quasi Fermi distributions, parameters ε F and T o Ideal cell voltage V = 1/e µ eh ε FC -ε FV = (ε g + 3 kt o ) (σ e + σ h ) T o 26

27 Conversion of solar heat, wide band absorbers; thermalisation to T o 27

28 Conversion of solar heat, narrow-band absorbers; iso-energetic thermalisation to T o 28

29 Thermodynamic analysis Compass bearings, cell architecture, examples Cooling of charge carriers to T o necessary, minimise entropy generation Selectivity of transport essential realise semi-permeable membranes hetero-junction cells (low surface rec.) redox system (dye cells) polymers Low irreversible entropy generation in carrier transport Optical concentration (where appropriate) 29

30 Thermodynamic analysis, continued Compass bearings, materials, examples Hot carrier cells: energetically narrow selective membranes absorber: very low e/h phonon interactions nanometer dimensions: absorber-membrane Intermediate band cells: very low non-radiative recombination via intermediate bands essential, metal type intermediate bands Multi exciton cells: back reaction seems to be detrimental 30

31 Thermodynamic analysis, continued Compass bearings, materials, examples Tandem cells (also other than III-V) exactly tuned absorber characteristics tunnel junctions, low recombination and absorption alternatively: mechanically stacked Generally: Use highly absorbing materials with radiative recombination only (highly fluorescing) 31

32 Concluding remarks PV energy conversion is a market-proven technology On the market: Silicon wafer cells, thin-film semiconductor cells Entering the market: III-V semiconductor-based concentrator systems, (plastic cells and dye cells) In particular for the proven technologies there is still large scope for incremental but essential and fare reaching optimisation and cost reduction 32

33 Concluding remarks, continued Thermodynamic analysis of photovoltaic energy conversion may be helpful for navigation towards novel cell architectures and materials 33

34 Thank you for your attention! More information 34