SOLAR CELLS Sun’s energy

Alexandre Edmond Becquerel Becquerel, A. E. "Le spectre solaire et la constitution de la lumière électrique." C. R. l'Acad. Sci., "shining light on an electrode submerged in a conductive solution would create an electric current." 1839 First steps; discovery of the PV effect

Following the discoveries of photovoltaic properties of selenium (1873) and selenium-platinum junction (1876) ; Willoughby SMITH, "Effect of Light on Selenium during the passage of an Electric Current", Nature, 20 February 1873, p.303. W. G. Adams and R. E. Day, “The action of light on selenium”, Proc. Roy. Soc. 25 (1876): First steps; discovery of the PV effect

Following the discoveries of photovoltaic properties of selenium (1873) and selenium-platinum junction (1876) ; In 1883, first solar cell was built by Charles Fritts with 1% efficiency. Very thin gold layer on top of selenium. First steps; discovery of the PV effect

Albert Einstein - On a heuristic viewpoint concerning the production and transformation of light. Annalen der Physik 17: , 1905 Asking “How?” and “Why?” Proved photoelectric effect. R.A.Millikan, “A Direct Photoelectric Determination of Planck’s ’h’ ”, Physical Review 7, 355–388 (1916).

Searching for “Cold Peace” in space In the early 1950s researches on solar cells gained speed (RCA labs, AT&T, Bell labs) First practical device fabricated in Bell labs with a 6% efficiency On 17 th March 1958, the first satellite powered by solar cells, Vanguard I, was launched (Hoffman electronics, 9% efficiency).

Searching for “Cold Peace” in space In the early 1950s researches on solar cells gained speed (RCA labs, AT&T, Bell labs) Fierst prtactical device fabricated in Bell labs with a 6% efficiency On 17 th March, the first satellite powered by solar cells, Vanguard I, was launched (Hoffman electronics, 9% efficiency). Followed by Explorer III, Vanguard II (USA), and Sputnik III (USSR) 1955 – First sun-powered automobile Illinois Sharp Corporation – first photovoltaic module from silicon solar cells 1970 – USSR – first highly effective GaAs heterostructure solar cells were fabricated by Zhores Alferov

Companies’ era In 1980s many companies were established and began a race to increase the output efficiency. By the introduction of MOCVD the efficiency of GaAs solar cell increased to 17% – ASEC- changing the substrate material led to invention of dual junction cells (20 %). Using multiple junction solar cells the efficiencies increased to 30 % levels in 2000s.

Record efficiencies (multiple-junction solar cells) Christiana Honsberg and Allen Barnett University of Delaware 42.8 % Dr. Frank Dimroth Fraunhofer Institute for Solar Energy Systems 41.1 % John Geisz National Renewable Energy Laboratory (NREL) 40.8 %

WHAT IS A SOLAR CELL? Basic loss mechanisms Reflectance losses Thermodynamic losses Recombination losses

Crystalline silicon c-Si Czochralski method

Thin film Advantageous due to less material usage Flexibility Lighter weights CdTe (easy to deposit, toxicity) CIS (CuInSe2) and CIGS (CuInxGa(1-x)Se2) GaAs multijunction (generally for space)generally for space Light absorbing dyes (DSSC) (Ruthenium metal organic dye ) Organic/Polymer

Concentrators

Wilfred G.J.H.M. van Sark, et. al., Optics Express, 16(26), 21773(2008).

Concentrators Science, 321, 11 July dyes: 4-(dicyanomethylene)-2-t-butyl-6- (1,1,7,7- tetramethyljulolidyl-9-enyl)-4H -pyran (DCJTB) platinum tetraphenyltetrabenzoporphyrin [Pt(TPBP)] Host material: tris(8- hydroxyquinoline) aluminum (AlQ3)

Concentrators Science, 321, 11 July 2008.

Concentrators Comparison of an organic dye and QD Rowan, et. Al., Adv. Matr. Concepts for Luminescent Solar Concentrators, 14(5), 1312(Oct, 2008).

Concentrators Quantum Dot Solar Concentrators Low absorption coefficient Solubility with QDs High luminescence when cast with QDs Chemical durability Non-toxic Low cost For efficient light concentration QDs and the carrier material should be compatible. It is important to the carrier material have following properties: Efficiently absorb solar energy Are intensely luminescent in the specral region of PV cell’s maximum sensitivity Mechanically strong Chemically stable Preserve their spectral-luminescent characteristics In addition the quantum dots should;

Concentrators Quantum Dot Solar Concentrators

Concentrators Quantum Dot Solar Concentrators

Concentrators Quantum Dot Solar Concentrators

Concentrators Quantum Dot Solar Concentrators

Concentrators Quantum Dot Solar Concentrators Result: 77% light retention