Light management in thin-filmsolar cells

Albert Polman

Center for NanophotonicsFOM-Institute AMOLF

Amsterdam, The Netherlands

Vanguard satellite 1958

The first practical solar panel (1954)

Bell Laboratories (1954)

2010

Price per solar Watt vs. installed power

P. Maycock

Black dots:

area of solar panels neededto generate allof the worlds primary energy (all energy consumed:electricity, heat, fossil fuels)

Solar irradiance on earth

assuming 8%

efficient photovoltaics

Available renewable energy sources

Solar cell basic geometry

Solar cell operation

Effects of Rshunt and Rseries on I-V curve

Ideal IV curve

Low Rsh

High Rse

Rsh = ∞

Rse = 0

Light is poorly absorbed in a thin-film solar cell

Solar spectrum absorbed in 2 m thick Si film

“Quantum defect” limits efficiency

Photons arequantizedenergy packets:

A 2 eV photon willgive create max.1 Volt over thep-n junction

A 0.5 eV photon is not absorbed

Eg(Si)=1.1 eV

Triple-junction tandem solar cell

1.5 V

1.0 V

0.5 V

Record efficiency solar cell

From: Richard King (Spectrolab)

Triple-junction tandem solar cell layer geometry

Efficiency limits of different solar cell types (2010)

3-junction tandem

crystal Si wafer

thin film:CdTepoly-Siamorphous Siorganic/polymerdye-sensitizedother

Too expensive

Too low efficiency

2009: CdTe thin film cellscosts: < 1 $/W

Relative abundance of elements vs. atomic nr.

from P.H. Stauffer et al, Rare Earth Elements - Critical Resources for High Technology, USGS (2002)

Materials resources are limited

Solutions:1) Earth Abundant

Semiconductors (Si,Cu2O, Zn3P2, FeS2)

2) Enhance Light Absorption/reduce semiconductor volume

Requirements to construct 1 TW of PV with optically thick cells at 15% efficiency

Photovoltaic materials production and reserve base

Si solar cell efficiencies

…

© Ron Tandberg