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Our Brilliant Half Century - PV Richard Corkish

Photovoltaics Early History - Becquerel

• Becquerel 1839

• Museum of Natural History in Paris

• 19 years old in 1839

• One of a dynasty of famous scientists

• Identical metal electrodes in electrolyte

• One electrode illuminated

• PHOTO-VOLTAGE & CURRENT!!

• Better with silver halide coating

• Unable to distinguish photoelectric and

photochemical effects

• Goldmann and Brodsky made

photovoltaic interpretation (Annalen der

Physik, vol. 44, pp. 849-900, 1914)

E. Becquerel, "Recherches sur les efféts de la

radiation chimique de la lumière solaire, au moyen

des courants électriques (Studies of the effect of

actinitic radiation of sunlight by means of electric

currents)“, Bibliotheque Universelle de Geneve,

vol. XXII, pp. 345-366 (plus figures), 1839.

Photovoltaics Early History – Becquerel Effect

• Sabine (1878) used selenium coating on

platinum electrodes

• Rediscovered by Minchin (1891) using

selenium, whose photoconductivity was already

known:

• Ignorant of Becquerel

• “the direct transformation of the radiant energy of

the sun into work useful for us, without the

consumption (at least on any large scale) of

materials on the earth – in other words to get rid of

that terrible waster of energy, the steam engine”

• Minchin made first astronomical electronic

photodetector measurements

B. Lange, Photoelements

and their Application. New York:

Reinhold, 1938.

Photovoltaics Early History – Cuprous oxide photolytic cells

• Attention moved to electrolytic Cu2O

cells

– Logarithmic dependence of VOC on light

intensity

– Great confusion of simultaneous

chemical/physical effects

– Chr. Winther proposed physical

explanation (1927) and chemical (1929)

• Essential similarity of solid-state

Cu2O photoeffect and electrolytic

Becquerel effect identified in 1930s

at Siemens Labs. (Schottky, Duhme,

Waibel)

WINTHER, C. 1929. Über den

Becquereleffekt. II. Zeitschrift

für physikalische Chemie

<Leipzig>, 81-96.

Photovoltaics Early History – 1930s: Commercialisation of

Cuprous oxide photolytic cells

• “Rayfoto”: Cu/Cu2O cathode

• Pb anode; lead nitrate electrolyte – DC

voltage in dark

• Arcturus Photolytic

• Liquid electrolyte

• Gel electrolytes

• Solid electrolyte (moist NaCl)

1. Glass bulb

2. Cuprous oxide plate

3. Rock salt crystal

4. Wire electrode

5. Saturated NaCl solution

Photovoltaics Early History – Selenium in solid state

• Telegraph clerk May discovered Se

photoconductivity, 1873 (published by

his boss: Willoughby Smith)

• Adams & Day (1877): “clearly proving

that by the action of light alone we could

start and maintain an electrical current in

the selenium” • First solid state PV

• Claimed effect due to extra light-induced crystallisation in the material

• Barrier effects at contacts

• Fritts (1884) • Se melted onto Cu plate

• Endorsed by Siemens (1885) as “an entirely new phenomenon, which is of greatest scientific importance”

• Ignorant of prior work of Adams & Day, Kalischer

Experimental arrangement

of Adams & Day

(from Green, 1990)

Fritts’ cell. Fig. from

Barnard, 1930

Photovoltaics Early History – Selenium in solid state

• Se rediscovered in 1930s – Lange and Eitel (1930)

– Bergmann (1931)

– Applied frontwall cell idea, borrowed from Cu2O

• Se eclipsed Cu2O

• Semitransparent, rectifying metal front contact

Lange (1938) Summer (1957)

Photovoltaics Early History – Cuprous oxide in solid state

• Kennard and Dietrich (1917) • Surface potential change under

illumination in both Se and Cu2O

• “under illumination this E.M.F. increased by 7 mV. when the top contact was unshaded but decreased by the same amount when the contact was shaded”

• Ignored for decades

• Rediscovered in 1920s and 1930s: 4 major research groups - 2 in Germany, 1 in USA, 1 Soviet Union

• Grondahl and Geiger (1927) defended priority over Lange

Grondahl and Geiger, British Patent

277,610

Photovoltaics Early History – Cuprous oxide in solid state

• Lange (Kaiser Wilhelm Institute, Berlin)

• Independent discoveries

• Sputtered thin metal film as front contact (improved on Grondahl method)

• “It is really astonishing that the enormous energy of the sun, which our earth receives daily ... is not transformed into other forms of energy. But it is still more astonishing that we have not changed the light, whose electromagnetic character we have known for decades and whose field strength amounts to several volts per centimetre, into useful electric energy and converted the displacement currents of the light into electrical conduction currents.”

• Schottky (1930) developed theory

• Main potential drop was across metal-semiconductor barrier layer

• Barrier region critical for photogeneration

• Thought photogeneration occurred only at junction.

Photovoltaics Early History – More theory

• Frenkel & Joffé (USSR, 1932) • Maxwellian distribution of electron energies

• Explained disappearance of rectification at high T

• Exponential dependence of I on V

• Mott (1939)

• Energy band diagram for metal-semiconductor diode and photocell

• p-type Cu2O

• Schottky included depletion layer and partially depleted layer

• Basis for modern p-n junction theory

Image: Zworykin (1949)

Photovoltaics Early History – Other Materials

• Argentite (Ag2S), 1922

• Molybdenite (MoS2), 1924

• Thallium sulphide (Tl2S), 1939

• Cuprite (Cu2S), acanthite (Ag2S), lead

sulphide (Pb2S), diamond, NaCl, KCl, etc.,

etc.

• Bergmann reported on PV in 37 materials

Photovoltaics Early History – Ge and Si

• Research in USA during WWII

• Ge: – Bell at MIT Radiation Lab. (1944)

– Benzer at Purdue U. for NDRC (1944, now declassified). Natural p & n.

• Sosnowski (PbS, 1947) predicted PV in Si & Ge (Benzer responded re Ge)

• Si: – preceded Ge

– Russel Ohl at Bell Labs

– Effect noted 23 Feb. 1940

– Patent filed 1941

– Accidental p-n junctions by cooling

– Vertical junction

– Horizontal junction

– Brattain explained p-n Feb. 1940

Photovoltaics Early History – Si at Bell Labs

• Miller and Greenblatt (1945) • PV in Si point contact diodes

• Fuller developed high-T vapour diffusion for large area junction

• D. M. Chapin, C. S. Fuller, and G. L. Pearson, "A new silicon p-n junction photocell for converting solar radiation into electrical power," Journal of Applied Physics, vol. 25, pp. 676-677, 1954.

• Deliberate p-n junction

• 6% conversion efficiency

• 14% by 1958

Images: Ohl patent (1941)

Photovoltaics Early History – Compound semiconductors and Si

• Reynolds (1954) • 6% from cuprous sulphide/cadmium sulphide

• Welker (1954): first GaAs report

• Jenny (1956): 6.5% from GaAs

• CdTe: RCA Labs. in 1955-1957

• Photovoltages possibly arising from p-n junctions between two organic materials reported by Meier and Haus (1960), and Needler (1965)

• 10% efficiency by 1955 at Bell Labs

• 14.5%: Mandelkorn et al. Journal of the Electrochemical Society 1962; 109: 313–318.

• ‘Violet’ cell developed at Comsat Labs in the early 1970s exceeded 15%

• Comsat non-reflecting cell using textured surfaces gave 16.7% in 1976

• Applications in spacecraft and dreams of terrestrial uses

Photovoltaics Early History – Applications

• P. A. Crossley, G. T. Noel, and M. Wolf, "Review and Evaluation of Past Solar-Cell Development Efforts," RCA Astro-

Electronics Division for NASA, Washington, D.C. Contract Number NASW-1427 (AED R-3346), June 1968 1968. [ UNSW Library: PQ537.54/11]

• P. Benjamin, The Voltaic cell: Its Construction and its Capacity, First ed. New York: John Wiley & Sons, 1893.

• G. P. Barnard, The Selenium Cell. Its Properties and Applications. London: Constable & Co., 1930.

• B. Lange, Photoelements and their Application. New York: Reinhold, 1938.

• W. Summer, Photosensitors A Treatise on Phot-Electric Devices and their Application to Industry. London: Chapman & Hall, 1957.

• J. Perlin, From space to Earth : the story of solar electricity. Ann Arbor, MI: Aatec Publications, 1999.

• M. A. Green, "Photovoltaics: Coming of age“, 21st IEEE Photovoltaics Specialists Conference, Kissimimee, Florida, 1990.

• M. Riordan and L. Hoddeson, Crystal fire : the birth of the information age, 1st ed. New York: Norton, 1997. (Bell Labs)

• C. E. Backus, "Solar Cells." New York: IEEE Press, 1976.

Photovoltaics Early History – Further reading

Photovoltaics Early History – Si cell development (Australia)

• Martin Green joined Lou Davies and established PV research at UNSW in 1974

• UNSW MINP cell demonstrated 18% efficiency in 1983

• Andrew Blakers studied PhD at UNSW established PV research at ANU in 1991, building on solar thermal history

• References: • John Perlin, J. (1999) From space to Earth : the story of solar electricity, Aatec Publications, Ann Arbor, MI.

• Hampton, B., Allen, B., and Loeffel, R. (2009) The History of the UNSW Faculty of Engineering 1949-2009, UNSW, Sydney.

• Hampton, B., and Allen, B. (2010) The History of the School of Electrical Engineering and Telecommunications 1949-2009, UNSW, Sydney.

• Tennant-Wood, R. (2012) Following the sun, ANU e-Press, Canberra.

Images: Green (2009)

All-rear contact silicon solar, ~1954 (Green, 2009)

Photovoltaics Early History – Si cell efficiency evolution

Green, Prog. PV 17, 183 (2009)

Photovoltaics Modern History – Australia’s Part

Silicon solar cell records Prof. Lou Davies and Dr Martin Green (1977)


• Metal-insulator-NP junction (MINP) cell (UNSW) • Thin passivating oxide under the contact

• 18.1% efficiency

• Passivated emitter solar cell (PESC) (UNSW) • Contact through openings in oxide

• Further improvement with microgroove texturing

• 21.4%


• Passivated Emitter and Rear Cell

• Passivated Emitter, Rear Locally (PERL) diffused cell

• Passivated Emitter, Rear Totally (PERT) diffused cell

• Passivated Emitter, Rear Floating (PERF) junction cell


• Passivated emitter & rear (PERC) solar cell (UNSW) • 22.6% efficiency

PERC Cell

• Passivated emitter real locally diffused (PERL) solar cell (UNSW) • Rear contact through openings in oxide to local diffusion

• Inverted pyramid texturing

• 25.0%

Silicon solar cell records Reference: Martin Green, in Practical Handbook of Photovoltaics, 2012


1976

First Lab –

1977, Martin

Green and

Bruce Godfrey

1977

At NASA – 1976:

Michael Godlewski

(NASA Lewis),

Martin Green, Bruce

Godfrey, Michael

Willison


First 20% cell 1985 Aihua Wang, Martin Green, Jianhua Zhao 1995


Green, Prog. PV 17, 183 (2009)


UNSW Group ~1992


• Screen printed solar cell • Industry norm (multi or mono Si)

• Best balance of cost/performance

• Silver paste front grid

• Wide lines to ensure continuity

• Heavy phosphorus doping for good contact but compromises current from blue, violet light

• Thick (>180µm) wafer for robustness

• Random texturing

• Low-risk investment


• Laser-grooved buried contact cell (UNSW) • Selective emitter (heavy doping at contacts only)

• Narrow, deep grid lines

• Commercialised by BP Solar as “Saturn”

• 50MW/y in 2003, ~5% of global production

• Powered “Spirit of Biel” to win 1990 World Solar Challenge

• Eliminates silver paste

• Higher efficiency but more process steps than screen print process

• Epi-Lift cell (ANU, Origin) • Fabrication of single-crystal silicon films,

• Epitaxial layers on single-crystal silicon

• Layers detached from the re-usable substrate

• Reduced Si demand

Blakers et al., Appl. Phys. A 69, 195 (1999)


• Crystalline Silicon on Glass (UNSW, Pacific Solar, CSG Solar, Suntech) • Deposit thin layer of amorphous silicon

on glass superstrate

• Anneal the layer to crystallise it

• Form solar cell in deposited layer

• Glass becomes cover glass

• 10–11% efficiency (small area modules)

• ~10 MW of 1.4m2 modules produced


• Elongated Cells (eg. SLIVER) (ANU, Origin, Transform)

• Narrow cells cut from thick wafers

• Lightweight

• Low silicon consumption

• Flexible modules

• More tolerant of partial shading of a module

http://peswiki.com/index.php

http://transformsolar.com http://transformsolar.com


• Semiconductor Finger Cell (UNSW) • Selective emitter

• Shallow grooves, diffused heavy doping

• Screen print orthoganal lines over insulator

• Small metal-silicon contact area

• Laser-doped selective emitter cell (UNSW) • Selective emitter (heavy doping at contacts only)

• Narrow, deep grid lines

• Commercialised by BP Solar as “Saturn”

• 50MW/y in 2003, ~5% of global production

• Powered “Spirit of Biel” to win 1990 World Solar Challenge

• Eliminates silver paste

• Higher efficiency but more process steps than screen print process

• Pluto (UNSW, Suntech) • Laser doped selective emitter

• localised laser-doped p-type regions at the rear

• record efficiencies for standard commercial p-type CZ wafers and multicrystalline silicon modules.

• 0.5GW annual production capacity


• Pacific Solar -> CSG

Solar -> Suntech R&D

Australia

• Australian Solar

Institute

• ARENA

• Australia – US

Institute for Advanced PV

• Australian Centre for

Advanced PV

Photovoltaics Systems – Western Australian leadership (Philip Jennings)

• Solar Energy Research Institute of WA (SERIWA) 1978 – 1987

• Systems design and component testing for RAPS was a high priority.

• Assisted the WA Govt with its successful RAPS subsidy program.

• Murdoch University Energy Research Institute (MUERI) 1987.

• Australian CRC for Renewable Energy (ACRE) in 1996 – 2004

• Research Institute for Sustainable Energy (RISE)

• ACRE and RISE assisted CAT to get the Bushlight Program underway in 2004.

• Advanced Energy Systems (AES) was started by Steve Phillips and Wal James from SERIWA/MUERI

• Regen Power develops modern hybrid RAPS systems for the mining industry.

• Module, inverter testing with Telstra, UNSW (ACRE) 1979 –

• Trevor Pryor (MUERI) 1987 grant from JQA - testing stations at Murdoch, Darwin, Alice Springs

Now and Beyond

• AUSIAPV/ACAP

• PP1 Silicon Cells

• PP2 Organic and Earth-Abundant Inorganic Thin-Film Cells

• PP3 Optics/Characterisation

• PP4 Manufacturing Issues

• PP5 Education, Training and Outreach

• Opportunity to be PV’s Silicon Valley!

• Graduates leading the global industry

• Suntech led in China

• Desert Knowledge Australia

• Bushlight gone international

• Future even brighter than past

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