HOW EFFICIENT MODERN SOLAR CELLS WORK.Yuichi Irisawa

SOLAR CELLS Solar cells convert sunlight to electricity directly Solar cells are classified some types

Silicon

Inorganic compound

semiconductor

Mono crystal

Poly crystal

Amorphous

HIT

CdTe

CIGS

MECHANISM OF SOLAR CELLS

Silicon solar cells made by 2 types of silicon When solar cells are received sunlight, electron and proton moves

to front electrode and back electrode Difference of potential is occurred, So electric current is produced

Sunlight

Current

N-type silicon

P-type silicon

P-N junction

Front electrode

Back electrode

Load

ElectronProton

HOW EFFICIENT SOLAR CELLS WORK

The efficiency of solar cells is about 13~17% The efficiency of solar cells which are developed in

laboratory is more than 24%

Module type EfficiencyCrystal silicon 13~17%Thin film silicon 15%Compound 13%Crystal silicon (in lab) More than 24%

FACTOR OF THE SOLAR CELLS EFFICIENCY

Spectral response Transmittance and reflectivity of cover glass

Sunlight wave length is mainly distributed from 300nm to 1300nm Solar cells are more efficient as much as cells receive wide range wave

Cover glass makes sunlight weaken and reflected Improve to high transmittance and low reflectivity

Wave length (nm)

Si sensibility

CIS sensibility

Sunlight spectrumSpec

tral

resp

onse Sunlight

Reflected light

Transmitted light

Solar cell

Cover glass

IMPROVE THE SOLAR CELLS EFFICIENT

Other way, solar cell made from 2 type layer is developing The cells can receive both short and long wave length sunlight So “hybrid” solar cells are more efficient than the cells which

made from 1 type layer

Middle layer

Cover glass

Back electrode

Amorphous cellFront electrode

Microcrystal Si cell

Short wave lengthLong wave length

CONCLUSION

Sunlight moves electron and proton to electrode, so electricity is produced

The solar cells efficiency is about 13~17% In order to improve efficiency,

Receive more sunlight wave for wide range High transmittance and low reflectivity of cover glass “Hybrid” solar cells are effective