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Overview of Solar Cell Technologies Overview of - Foresight Taiwan

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					Overview of Solar Cell Technologies



           Chung-Chih Wu (吳忠幟)
         Dept. of Electrical Engineering
          National Taiwan University
                    2008.6.24
Top Ten Issues This Century
      Why solar cells are likely to provide a
        significant fraction of our power

• We need ~ 30 TW of power, the sun gives us 120,000 TW.
  (1-hour sunshine ~ 1-year energy consumption)

• Solar cells are safe and have few non-desirable
environmental impacts.

• Using solar cells instead of burning coal to generate
electricity is a much easier way to reduce carbon emissions
than replacing gasoline in vehicles.
Area and cost needed to power a country




 (150 km)2 of Nevada covered with 15 % efficient solar
 cells could provide USA with enough electricity

                               J.A. Turner, Science 285 1999, p. 687.
                     Future…..

solar energy may become the major section of the energy
source ……
Types of Solar Cells
Progresses in solar cell efficiency
    Crystalline Si solar cells: The current industry leader

conventional p-n junction Si solar cell




 Modules
 • 12-15 % efficiency                               rough numbers
 • $350/m2
                                  Average cost of PV cell electricity: $0.27/kW-hr
 • $3/Wp (from manufacturer)
 • $6/Wp (installed)              Today’s grid electricity: $0.06/kW-hr
                                  (+ installation cost)
                               Multijunction tandem cells

Grid

n GaAs
AlInP                    n
                         n
                         p
GaInP (1.90 eV)

AlGaInP                  p
                         p++
                         n++
GaInP                    n
                         n
                         p

GaAs (1.42 eV)

GaInP                    p
                         p++
                         n++
GaAs:N:Bi                n
                         n
                         p
GaAs:N:Bi (1.05 eV)

GaAs:N:Bi                p
                         p++
                         n++
                         n        • ~40 % efficiency achieved (e.g. SpectroLab)
                         p

Ge Substrate (0.67 eV)            • Costs are estimated at $50,000/m2, so concentrators
                                  must be used.
                         Thin Film Solar Cells

A thin film of semiconductor is      CIGS (CuInGaSe2), CdTe
deposited (on glass, plastics,       World record: 16-19.5 %
metal foils etc.) by low cost        Stable
methods.                             Is there enough In in the world?
                                     Cd is toxic
Less material is used. (vs.
shortage in crystalline Si)          amorphous Si, uc-Si, tandem
                                     World record: 12-14 %
Cells can be flexible.               not completely stable

Possibly fabricated by effective
roll-to-roll process.                Nanostructured solar cells
                                     - dye sensitized solar cells (~11%)
(potential efficiency improvement    - polymer/polymer
and cost reduction)                  - polymer/organic
                                     - polymer/inorganic (nanocrystal)
                                       (~6%)
<1/100
material
usage
Generations of Si Thin Film Solar Cells
Light Trapping/Textured TCO
                      The cheapest option?


Efficiency: 0.3 %

We don’t have the
land and water to
provide the world
with energy this
way.

Can we artificially
improve the
efficiency?
               Nanostructured Solar Cells

                                                         acceptor
                                                         e-

                                                   E     h+

                                                    donor


                                                   Excitons are
                                                   split at
                                                   interfaces.
                                                   Separating
                                                   the electrons
                                                   and holes
                                                   enables the
                                                   use of low
                                                   quality
                                                   materials

January 2005 Materials Research Society Bulletin
Dye Sensitized Solar Cells (DSSC)
Bulk nano-heterostructure organic/hybrid solar cells
ordered bulk nan0-heterojunctions        low-bandgap materials




Almost all excitons can be split
No dead ends
Enhance transport/path
Polymer/organic chains can be aligned   Nature Materials, 2007. 6(7): p. 497-500
Tandem nanostructured solar cells




  A. J. Heeger et al., Science, 317, 222-225, 2007.
Global Solar Cell Production Forecast
            Taiwan Solar Cell Production Forecast

Valid only for one week??                      Unit : MWp
Taiwan RE Industry Target
PV (RE) Insudtry – next trillion NTD industry?
         Taiwan’s advantages in PV industry


1. Industry: ambitious PV players and strong
   manufacturing capability (quick investment/response,
   fast scale-up and then price killer/keeper??)
2. Excellent infrastructure: based on semiconductor,
   electronics, optoelectronics, TFT-LCDs, precision
   machinery industry experiences
3. R/D capability: universities, ITRI, INER, Chung-san
   Institute of Science and Technology etc.
4. Strong government support/commitment
Thank you for your attention

				
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