Amorphous and Nanocrystalline Silicon in Solar Cells

1. Silício amorfo e nanocristalino e a sua aplicação em células solares S.A. Filonovich CENIMAT/I3N, Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa, 2829-516 Caparica, Portugal

2. Amorphous and nanocrystalline silicon and its application in solar cells S.A. Filonovich CENIMAT/I3N, Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa, 2829-516 Caparica, Portugal

3. Team: • Ms. Student: Diana Gaspar • Researcher: Andrea Cardoso • PhD Students: Antonio Vicente • Iwona Bernacka-Wojcik • Ioan-Bogdan Diaconu • PhD researchers: Sanjay Ram • Sergej Filonovich • Hugo Aguas • Isabel Fereira • Coordinator: Prof. Rodrigo Martins

4. Outline • 1. Introduction • 1.1 Solar cell generations; • 1.2 Types of silicon (crystalline, a-Si:H, μc-Si:H, nc-Si:H); • 1.3 Chemical Vapor Deposition • 2.Single junction and Tandem solar cells • 3. Solar Cells @ CENIMAT/I3N • 3.1 Facilities • 3.2 Running and starting projects • 4. Conclusion

5. 1. Introduction 1.1 Solar cell generations

6. 1. Introduction 1.1 Solar cell generations First generation

7. 1. Introduction 1.1 Solar cell generations First generation 86% of the solar cell market Multicrystalline Silicon Cells Monocrystalline Silicon Cells η ~ 15 % (24,7%) η ~ 12 % (20.3%)

8. 1. Introduction 1.1 Solar cell generations Second generation

9. 1. Introduction 1.1 Solar cell generations Second generation – thin-film solar cell Amorphous Silicon Micromorph – a-Si:H with μc-Si:H η ~ 10 % (14.5%) η ~ 6-7 % (9,5%)

10. 1. Introduction • 1.1 Solar cell generations Third generation

11. 1. Introduction • 1.1 Solar cell generations • Third generation solar cells : • nonsemiconductor technologies (including polymer-based cells), • quantum dot technologies, • dye-sensitized solar cells, • upconversion technologies.

12. 1. Introduction 1.2 Types of silicon

13. 1. Introduction 1.2 Types of silicon

14. 1. Introduction monocrystalline amorphous short-range order long-range order

15. 1. Introduction monocrystalline amorphous short-range order 8 % of Si-Si bond angles variation 1 % of Si-Si bond lengths variation

16. 1. Introduction monocrystalline amorphous short-range order 8 % of Si-Si bond angles variation 1 % of Si-Si bond lengths variation high density of strained or week Si-Si bonds their energy levels are located in the band tails

17. 1. Introduction monocrystalline amorphous Lack of periodicity in a-Si:H implies a relaxation of the requirement of conservation of the wavevector for interband transitions in opto-electronic processes. Thus, a-Si:H behaves as a direct-bandgap material and its red-light absorption is much higher than that of crystalline silicon.

18. 1. Introduction monocrystalline amorphous dangling bond density in non-hydrogenated silicon is about 1019-1020 cm-3

19. 1. Introduction monocrystalline amorphous in a-Si:H with 10 at.% of hydrogen defect density is decreased to 1016 cm-3

20. 1. Introduction polymorphous (nanostructured) Si relaxed amorphous matrix nanocrystalline silicon particles P. Roca i Cabarrocas, Thin Solid Films 403 –404 (2002) 39–46

21. 1. Introduction • 1.3 Chemical Vapor Deposition • is a chemical process used to produce solid materials with desired properties and purity from the gas phase

22. 1. Introduction • 1.3 Chemical Vapor Deposition • is a chemical process used to produce solid materials with desired properties and purity from the gas phase. • In the case of intrinsic a-Si:H and nc-Si:H typical precursors are: silane (SiH4) and hydrogen (H2).

23. 1. Introduction • 1.3 Chemical Vapor Deposition • is a chemical process used to produce solid materials with desired properties and purity from the gas phase. • In the case of intrinsic a-Si:H and nc-Si:H typical precursors are: silane (SiH4) and hydrogen (H2). To achieve n-type doping phosphine (PH3) is used To achieve p-type doping diborane (B2H6) or trimethylboron (B(CH3)3) are used.

24. 1. Introduction • 1.3 Chemical Vapor Deposition Plasma-Enhanced CVD (PECVD) parameters influencing the growth: • Chamber geometry;

25. 1. Introduction • 1.3 Chemical Vapor Deposition Plasma-Enhanced CVD (PECVD) parameters influencing the growth: • Chamber geometry;

26. 1. Introduction • 1.3 Chemical Vapor Deposition Plasma-Enhanced CVD (PECVD) parameters influencing the growth: • Chamber geometry;

27. 1. Introduction • 1.3 Chemical Vapor Deposition Plasma-Enhanced CVD (PECVD) parameters influencing the growth: • Chamber geometry; • Gas Pressure; • Power Density; • Excitation Frequency (RF, VHF); • Substrate temperature; • Electrode to substrate distance; • Flow Rates of the gases; • Gas Composition (e.g. Hydrogen dilution);

28. 1. Introduction • 1.3 Chemical Vapor Deposition influence of hydrogen dilution: R.W. Collins, et al., Solar Energy Materials & Solar Cells, 78 (2003) 143–180

29. 1. Introduction • 1.3 Chemical Vapor Deposition influence of pressure of working gases: high pressure regime low pressure regime P. Roca i Cabarrocas, et al., Plasma Phys. Control. Fusion 50 (2008).

30. 2. Single junction and Tandem solar cells

31. 2. Single junction and Tandem solar cells

32. 2. Single junction and Tandem solar cells nc-Si:H solar cell a-Si:H solar cell Al n Al n I 300 – 500 nm I 2000 – 3000 nm Eg= 1.6-1.8 eV p Eg= 1.2-1.5 eV TCO p glass TCO glass

33. 2. Single junction and Tandem solar cells Tandem (micromorph) solar cell: top a-Si:H solar cell and bottom nc-Si:H one

34. 2. Single junction and Tandem solar cells Tandem (micromorph) solar cell: top a-Si:H solar cell and bottom nc-Si:H one

35. 2. Single junction and Tandem solar cells Journal of Non-Crystalline Solids, 338-340 (2004) 639

36. 2. Single junction and Tandem solar cells Journal of Non-Crystalline Solids, 338-340 (2004) 639

37. 3. Solar Cells @ CENIMAT/I3N Facilities

38. 3. Solar Cells @ CENIMAT/I3N Facilities: Clean room Class 1000 Class 10 000 Materials’ production Patterning

39. 3. Solar Cells @ CENIMAT/I3N Facilities: CVD and PVD r.f. Magnetron sputtering (total=6) PECVD (total=6)

40. 3. Solar Cells @ CENIMAT/I3N Facilities: new CVD and PVD systems

41. 3. Solar Cells @ CENIMAT/I3N Facilities: new CVD and PVD systems

42. 3. Solar Cells @ CENIMAT/I3N Running projects and starting projects:

43. 3. Solar Cells @ CENIMAT/I3N Running projects and starting projects: with industies: SolarTiles (ADI-2009/003380) NanoSi – PVCell (QREN/NANOSI-PVCELL) FCT project: 3. Nanomorph (PTDC/CTM/099719/2008) Starting I3N project 4.HybridSolar

44. 1. Solar Cells @ CENIMAT/I3N Running projects: SolarTiles

45. 3. Solar Cells @ CENIMAT/I3N Running projects: SolarTiles Main goal : development of amorphous silicon nip solar cells on ceramic substrates

46. 3. Solar Cells @ CENIMAT/I3N Running projects: SolarTiles 1st attempt to combine design and technology NIP cell –VOC measurment with natural illumination.

47. 3. Solar Cells @ CENIMAT/I3N Running projects: NanoSi-PVcells Project promoted by: SOLAR PLUS (Portuguese enterprise of amorphous silicon PV modules) Main goal : development of: 1- nanocrystalline silicon pin solar cells; 2- heterojunctions 3- pin solar cells on plastic substrates

48. 3. Solar Cells @ CENIMAT/I3N Running projects: Nanomorph PTDC/CTM/099719/2008 – High deposition rate of nanomorph solar cells by using novel deposition conditions Main goal : 1- optimization of deposition processes in new CVD systems; 2- growth of polymorphous and nanocrystalline Si SCs; 3- growth of tandem “nanomorph” SCs.

49. 3. Solar Cells @ CENIMAT/I3N Starting project: HybridSolar(I3N) Hybrid Si-nanoparticle/polymer layers for solar cell applications IPC (Institute for Polymers and Composites) University of Minho CENIMAT (Materials Research Center)New University of Lisbon, FSCOSD(Physics of Semiconductors, Optoelectronics and disordered Systems) University of Aveiro Main goal: 1) to develop and understand the physical and chemical properties of hybrid Si-nanoparticles/polymer composites; 2) fabricate and test bulk heterojunction solar cells based on these hybrids by spin-coating and inkjet printing.

50. HybridSolar HybridSolar Hybrid Si-nanoparticle/polymer layers for solar cell applications