Photovoltaics: Energy for the New Millennium - Technology-Progress and Status Progress and Status

Photovoltaics: Energy for the New Millennium - Technology-Progress and Status Progress and Status

Loading
Loading Social Plug-ins...
Language: English
Save to myLibrary Download PDF
Go to Page # Page of 36

Description: World PV Module Shipments (MW) Progress in Laboratory Efficiencies Progress and Status Research Issues and Directions: Crystalline Silicon PV EFG Silicon Cylinders Thin-Film Amorphous Silicon Film Cadmium Telluride Copper Indium Diselenide (CIS) Novel PV Concepts.

 
Author: Thomas Surek , National Renewable Energy Laboratory (Fellow) | Visits: 2625 | Page Views: 2632
Domain:  Green Tech Category: Photovoltaics/Solar Subcategory: Solar 
Upload Date:
Short URL: http://www.wesrch.com/energy/pdfTR1L02KEKLTJM
Loading
Loading...



px *        px *

* Default width and height in pixels. Change it to your required dimensions.

 
Contents:
National Center for Photovoltaics

Photovoltaics: Energy for the New Millennium
Thomas Surek
National Renewable Energy Laboratory Golden, Colorado, U.S.A. tom_surek@nrel.gov http://www.nrel.gov/ncpv
02679666

National Center for Photovoltaics

Photovoltaics (PV) � Direct conversion of sunlight to electricity

Advantages � Modular (mW to many MW) � No (or few) moving parts � Noise and pollution free � Reliable; low operating costs � Abundant, indigenous resource (30,000 km2 PV for 700 GW)

02679658

National Center for Photovoltaics

Photovoltaic Technology--Progress and Status
200 160 120 80 40.2 46.5 40 26.0 29.2 33.6 0 1986 1988 1990

World PV Module Shipments Consumer and Commercial (MW)
Rest of the World Europe 125.8 Japan U.S. 88.6 77.6 69.4 55.4 57.9 60.0

201.3

20 16 Efficiency (%) 12 8 4 CuInSe2 CdTe Amorphous silicon (stabilized)
Kodak Boeing Monosolar Matsushita Kodak Boeing Univ. of So. Florida BP Solar Boeing ARCO NREL NREL

154.9

EuroCIS Boeing Univ. of So. FL Photon Energy AMETEK United Solar

Boeing Univ. of Maine

1992

1994

1996

1998

Source: PV News, February 2000

0 1975

The Best One-of-a-Kind Laboratory Cell Efficiencies for Thin Films (Standard Conditions)
1985 1990 1995 2000

1980

� World market (1999): 201.3 MW, ~$1.7 billion � Average growth rate (1994�99): >20% � Remote markets (telecommunications, developing
countries); PV/buildings � Module and system prices decreasing � New products and applications � Manufacturing capacities increasing: crystalline Si dominates, but thin film scale-up underway

� Record laboratory efficiencies, new materials, and
innovations � Commercial product efficiencies and reliability increasing � Multiple technology paths � Crystalline silicon (ingot- and non-ingot-based) � Thin films (amorphous Si, CdTe, copper indium diselenide) � Concentrators and high efficiency

02679601

National Center for Photovoltaics

220 200 180 160 140 120 100 80 60 40 20 0 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999
Source: PV News, February 2000
02679619

World PV Module Shipments Consumer and Commercial (MW)
Rest of the World Europe Japan U.S. 69.4 77.6 88.6 125.8 154.9

201.3

33.6 26.0 29.2

40.2

46.5

55.4 57.9 60.0

National Center for Photovoltaics

Progress in Laboratory Efficiencies
Conversion efficiency (%) Concentrator cells 30 Flat-plate crystalline silicon cells 20 Flat-plate thin films
02669404 02679662

40

10

Commercial module efficiencies lag 10�15 years behind laboratory efficiencies 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998

0

National Center for Photovoltaics

20 CuInSe2 16 Efficiency (%) CdTe Amorphous silicon (stabilized) 12
Boeing Monosolar Matsushita Boeing Univ. of Maine Kodak Boeing Kodak Univ. of So. Florida BP Solar Boeing ARCO NREL NREL

EuroCIS Boeing Univ. of So. Florida

Photon Energy AMETEK United Solar

8

4 0 1975

The Best One-of-a-Kind Laboratory Cell Efficiencies for Thin Films (Standard Conditions)
1985 1990 1995 2000
02679620

1980

National Center for Photovoltaics

Crystalline Silicon (Ingot-Based) PV--Progress and Status

Key companies: BP Solarex, Siemens Solar, Kyocera, AstroPower, Solec/Sanyo, Sharp, Photowatt, Shell � ~85% of today's market � 150 MW capacity (to double in near-term) � Proven products, 20-year warranties � Large ingots: 100 kg CZ, 200 kg casting � Multiple ingots w/ melt replenishment � Wire saw: < 300 �m wafers, < 200 �m kerf

Efficiency Status Cells Modules Float-zone 24.7 22.7 Czochralski 22.0 13�15 Cast poly 19.8 10�13 � Batch/continuous processing � High-efficiency devices in production � Well-developed technology base--new understanding of defects/impurities � Continuous electromagnetic casting in production

02679603

National Center for Photovoltaics

Crystalline Silicon (Ingot-Based) PV-- Research Issues and Directions
B Concentration (atoms/cm3) vs. Depth (�m)

�m

� Impurity/defect gettering and passivation � Czochralski "tri-crystals" to strengthen thin wafers � High-throughput, low-cost, high-efficiency processes-- � Thin-wafer (down to 100 �m) handling rapid thermal processing? � Wire-saw slurry recycling � Environmentally benign processing; waste-stream � Dedicated silicon feedstock supply--new processes
reduction � Manufacturing automation and module packaging for 30-year life for "solar grade" silicon? � Novel purification for mg-silicon (e.g., porous silicon etching/gettering)

02679604

National Center for Photovoltaics

Crystalline Silicon (Non-Ingot-Based) PV-- Progress and Status

Key companies: ASE Americas, Evergreen Solar, AstroPower, Ebara Solar, Bayer, Pacific Solar, Kaneka � Status varies from prototype modules to pilot production to commercial products � Proven products (~ 3% of market) � Capacity increases underway--few tens of MW in near term

Efficiency Status Cells Modules EFG 14�15 10�12 String ribbon 14�15 10�12 Thick Si/substrate 16.6 >10 Dendritic web 16�17 14 Thin Si/substrate up to 11 n/a � Improved performance from defect/ impurity and passivation studies � New interest in thin silicon growth

02679605

National Center for Photovoltaics

Crystalline Silicon (Non-Ingot-Based) PV-- Research Issues and Directions

� Manufacturing yield and throughput � Novel processing for continuous sheets � Impurity/defect gettering and passivation � New technology directions

� Thin silicon on low-cost substrate

� ASE Americas -- 1 m diameter cylinders � Evergreen -- < 100 �m thick, wide ribbon � AstroPower -- < 50 �m, monolithic interconnects on substrate

� Fast deposition rate (> 1 �m/min) � Grain size comparable to thickness � Diffusion length greater than thickness � Insulating substrate for interconnects � Many novel approaches: solid-state recrystallization, nucleation and growth, LPE, CVD, CVT, laser ablation, ... � Orientation-independent processes for light-trapping and passivation in thin Si
02679606

National Center for Photovoltaics

EFG Silicon Cylinders -- ASE Americas

Current: 0.5 m diameter 150 �m thick Future: 1.0 m diameter 10% efficiency � Lacking fundamental scientific and engineering base for materials/devices � ES&H issues studied and under control (e.g., recycling)--Cd perception issue?

National Center for Photovoltaics

Thin-Film Cadmium Telluride PV-- Research Issues and Directions
GRAIN BOUNDARY

SIMS Profile of Cu Diffusion

Thick ZnTe:Cu Thin ZnTe:Cu

� Film deposition development

� Front and back contacts

� Nucleation and growth � Gas-phase or surface chemistries � Annealing and heat treatment (CdCl2) � Grain growth, native defects, dopants � CdS/CdTe interdiffusion � Alternate transparent conductors; impact on film growth � Successful first-time manufacturing

� Alternate transparent conductors � Low resistance, stable back contacts � Role of Cu; Cu-free contact strategies? � Close efficiency gap (cell �> module) � Compatibility of manufacturing process steps (e.g., tie to glass float-line?) � Low-cost module packaging for long-term reliability (>20 years) � Accelerated module test procedures

02679610

National Center for Photovoltaics

Thin-Film Copper Indium Diselenide (CIS) PV-- Progress and Status
MgF2 (0.1 �m)--anti-reflection coating ZnO (0.4 �m)--transparent conducting oxide CdS (0.05 �m)--n-type window CuInGaSe2 (3.0 �m)--p-type absorber Mo (1.0 �m)--back contact

Glass (1�3 mm), plastic, or stainless steel foil--structural support

Key companies: Siemens Solar, Global Solar/ITN, ISET, EPV, Wurth Solar, Showa/Shell � Prototype production started in 1998: � First commercial products (5�10 W) � Efficient, large modules (>12%) � Expansion to multi-MW in near term � Field testing of modules shows promise; >10 years outdoors, no degradation

Efficiency status: Cell 18.8 Submodule 14.7 Module 12.1 Commercial >10 Others: Stainless steel substrate 17.5 Electrodeposition 15.4 With ZnO (no buffer) 15.0 � Alloying with Ga and S; role of Na � Progress mostly empirical; little understanding of materials/devices/processes

02679611

National Center for Photovoltaics

Thin-Film Copper Indium Diselenide (CIS) PV-- Research Issues and Directions
Electrodeposited CIGS Precursor Film Absorber CIGS from Electrodeposited Precursor Film

� Scalability of current processes

� Device research and development

� Predictive models of materials growth, devices, and processes � Real-time process controls � Yield and throughput � New techniques and materials � Non-vacuum approaches � Low-temperature depositions

� Heterojunction vs. homojunction � Role of window materials; improvements in blue response � Alternate front and back contacts � Higher bandgaps and multijunctions � Device models and characterization � Theory: Band structures, optoelectronic properties, defect physics, doping

02679612

National Center for Photovoltaics

High-Efficiency and Concentrator PV--Progress and Status

Key companies: PV International, Entech, Amonix, Sunpower, Tecstar, Spectrolab, Honda, BP Solar � Manufacturability demonstrated � Low-concentration, line focus � High-concentration, point focus � High efficiency cells (Si, GaAs, multijunctions) in production � Limited applications in today's markets

Si (up to 400X) 27 GaAs (up to 1000X) 28 GaInP2/GaAs (1X) 30.3 GaInP2/GaAs (180X) 30.2 GaInP2/GaAs/Ge (40�560X) 32.3 � Module efficiencies: 15-17% (Si); best prototypes: >20% (Si), >24% (GaAs), 28% (GaInP2/GaAs/Ge at 10X � Large space markets drive GaInP2/GaAs commercial cell production
02679613

Efficiencies:

National Center for Photovoltaics

High-Efficiency and Concentrator PV-- Research Issues and Directions
Calculated efficiencies (ideal) � Want 1 eV material lattice-matched to GaAs 500X AM1.5D: 36% 47% Try GaInNAs one sun AM0: 31%
1.8 eV

52% 41% GaInP 1.8 eV GaAs 1.4 eV New 1.0 eV Ge 0.7 eV

38% GaInP 1.8 eV GaAs 1.4 eV New 1.0 eV

GaInP

GaAs 1.4 eV

4

5

6 7 8 9

Energy (eV)

1

2

3

4

In production

Future generation

� High-efficiency (>40%) multijunctions

� �

� GaInAsN and Ge for 3rd and 4th cells � Lattice match to GaAs � Short diffusion lengths to date Monolithically integrated modules (e.g., for dish concentrators) New products for today's markets

� Novel concentrating concepts:



� Reflecting troughs � Concentrating dish � PV/thermal hybrids � Non-imaging optics � Low-profile concentrators Standards for qualification and performance testing of concentrators
02679614

National Center for Photovoltaics

Novel PV Concepts and New Materials-- Research Issues and Directions

Nanoparticle-derived precursors for PV � Potential for very low cost � Low process temperatures, non-vacuum � Potential for smooth, dense films � Absorbers (CdTe, CIS, ...) � Transparent conductors (SnO2, CdS, ...) � Contacts (Ag, Au, Pt, ...) � Nanocrystals, nanotubes, nanorods � Nanocharacterization

Dye-sensitized TiO2 photochemical cells � Potential for very low cost � Nanocrystalline TiO2, with monolayer dye sensitizer, in liquid electrolyte � 11%-efficient cell; scale-up for consumer products underway � Dye stability issue � Gel or solid-state electrolytes � Photoelectrochromic window (with WO3)

02679615

National Center for Photovoltaics

Novel PV Concepts and New Materials-- Research Issues and Directions
100
Room heat Room heat

Absorbance (%)

80 60

SnO2
Quartz shield Exhaust Window Matched emitter Cooling fins Propane

Cd2SnO4 40 20 0 0.4 0.8 1.2 Wavelength (�m) 1.6 2.0

PV array

Combustion Cooling Cooling air air Fan air

Transparent conducting oxides � Critical component in thin-film devices � Conventional TCOs: In, Sn, Zn-based � New/improved materials: high mobility key � Non-oxides, p-type TCOs, single crystals � Theory for defects, doping, role of grain boundaries � For PV: thin, high rate/low T, non-toxic, good electrooptical properties, easy to etch

Thermophotovoltaics (TPV) � Conversion of IR radiation (1300�1800� K) by low-bandgap (0.3�0.7 eV) PV cells � Many fuel choices and radiators; system design includes heat recycling/recovery � High power densities (1�5 W/cm2) � Single and multijunction III-V cells: GaSb, InGaAs, GaInAsSb; thin-film PV cells � Many applications and system concepts; prototypes available on market

02679616

National Center for Photovoltaics

PV Cell and Module Efficiency Measurements

Eff = 10.4%

Eff = 18.8%

� Efficiency measurements with respect to standard reporting conditions � Multiple test-beds for accurate and reliable results � Any PV cell or module technology � Spectrally adjustable light sources for multijunction devices � Concentrator cells (to 2000 suns) � Reference cell calibrations

� Spectral response measurements: - Extended wavelength range - QE of each cell in a module - Measure non-uniformities in photocurrent
02679665

National Center for Photovoltaics

Analytical Microscopy -- Microcharacterization Labs
AFM ASEM

(a)

M o

CIGS

ITO

(c)
EPMA STEM
Twin boundary

Device junction

(b)
5 nm

� Structural, topographical, chemical, defect, and electrical properties of PV materials and devices � Down to atomic-scale resolution

(a) AFM studies of recrystallization of polycrystalline CdTe versus treatment (b) ASEM cross-section of CdS-less CIGS with EBIC linescan showing junction location (c) Atomic structure of defects in CdTe by TEM

02679664

National Center for Photovoltaics

S ubm icron U ltrafast Studies on PV M at eria ls
1000 Photoluminescence (arb. units)

100

10

1

Ultrafast Near-Field Scanning Optical Microscopy (NSOM): � Spatial resolution = 0.1 micron � Time resolution = 1 psec � Directly probe effects of passivation on recombination at defects

0

1

2 Time (nsec)

3

4

Time-resolved photoluminescence (TRPL) across a grain boundary: � CdTe bicrystal -- lifetime at grain boundary(lower curve) decreases by factor of 2 compared to few microns from boundary (upper curve)

02679663

National Center for Photovoltaics

PV Markets and Applications -- International
Rural electrification: � Water pumping � Desalination/disinfection
Brazil India

India Brazil

China

South Africa

Home and security lighting
02679653

National Center for Photovoltaics

PV Markets and Applications -- International
Rural electrification: Schools and clinics

Zambia

India

South Africa Brazil Mexico

Village power

02679654

National Center for Photovoltaics

PV Markets and Applications -- Domestic
Remote, off-grid power: � Telecommunications � Signaling

� Disaster mitigation � Emergency power
02679656

National Center for Photovoltaics

PV Markets and Applications -- Domestic
Remote, off-grid power: � Water pumping � National Parks

� Stand-alone power � EV charging
02679652

National Center for Photovoltaics

PV Markets and Applications -- Buildings
Grid-connected: Commercial and residential

02679655

National Center for Photovoltaics

Some FAQs Concerning Photovoltaics
� Balance-of-Systems (BOS) components issues? � Materials availability: limits to large-scale PV? � Is photovoltaics safe? � What is energy payback period for PV systems? � How much land area for large-scale PV?

02679667

National Center for Photovoltaics

Balance-of-Systems (BOS) Components

� Key companies: Trace, S&C (Omnion), Applied Power (Ascension), UPG, AES, Mastervolt, NKF, Nippon Denchi, Toshiba � BOS related to area (e.g., installation), power (e.g., inverter, storage), and applications (e.g., pumps, lights) � 30�70% of today's system cost; source of nearly all reliability issues � Proven inverters (2�4 kW and 20 kW); experimental for 100s of kW � Hybrid systems; new ac-modules

� Reliability addressed by HALT and quality programs in manufacturing: - Improved MTBF (30,000 to 114,000 h) - Reduced failure rates (14% to 2%) � Research issues and directions: - Interconnection and islanding - Surge resistance (lightning, transients) - Advanced inverters (e.g., soft switching) - Battery management - Reliability testing; standards - Lower costs and improved reliability

02679671

National Center for Photovoltaics

Materials Availability: Limits to Large-Scale PV?
Percent of Today's Production for 1 GW PV
40 30 20 10 0

Drinkard Metalox

Indium

Tellurium

Gallium*
*
Subscribe
x