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5 1.1 Solar cell generations

First generation

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

1.1 Solar cell generations Second generation

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

1.1 Solar cell generations Third generation

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

1.2 Types of silicon

DescriptorSymbolGrain SizeCommon Growth Techniques Single crystalsc-Si>10 cmCzochralski (CZ) float zone (FZ) Multicrystallinemc-Si1 mm-10 cmCast, sheet, ribbon Polycrystallinepc-Si1 µm-1 mmChemical-vapor deposition Microcrystallineµc-Si<1 µmChemical-vapor deposition Nanocrystallinenc-Si<50 nmChemical-vapor deposition Polimorphous/protocry stalline/nanostructured pm-/pc- /ns-Si:H <3 nmChemical-vapor deposition Amorphousa-Si-Chemical-vapor deposition

short-range order monocrystalline amorphous long-range order

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

short-range order monocrystalline amorphous 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

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. monocrystalline amorphous

dangling bond density in non-hydrogenated silicon is about cm -3

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

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

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

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).

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.

1.3 Chemical Vapor Deposition Plasma-Enhanced CVD (PECVD) parameters influencing the growth: Chamber geometry;

1.3 Chemical Vapor Deposition Plasma-Enhanced CVD (PECVD) parameters influencing the growth: Chamber geometry;

1.3 Chemical Vapor Deposition Plasma-Enhanced CVD (PECVD) parameters influencing the growth: Chamber geometry;

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);

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

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

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32 n Al glass TCO p I 300 – 500 nm nc-Si:H solar cell a-Si:H solar cell n Al glass TCO p I 2000 – 3000 nm E g = eV E g = eV

33 Tandem (micromorph) solar cell: top a-Si:H solar cell and bottom nc-Si:H one

34 Tandem (micromorph) solar cell: top a-Si:H solar cell and bottom nc-Si:H one

35 Journal of Non-Crystalline Solids, (2004) 639

36 Journal of Non-Crystalline Solids, (2004) 639

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38 Class Class 1000 Materials’ production Patterning

39 PECVD PECVD (total=6) r.f. Magnetron sputtering r.f. Magnetron sputtering (total=6)

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45 Main goal : development of amorphous silicon nip solar cells on ceramic substrates

1st attempt to combine design and technology NIP cell –V OC measurment with natural illumination.

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

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.

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

51 "Let there be light!" Bible illustration by Gustave Doré, "Let there be electricity as well!" Thank you for your attention!!!