HOW EFFICIENT MODERN SOLAR CELLS WORK.
Yuichi Irisawa
SOLAR CELLS
Solar cells convert sunlight to electricity directly
 Solar cells are classified some types

Mono crystal
Poly crystal
Silicon
Amorphous
HIT
Inorganic
compound
semiconductor
CdTe
CIGS
MECHANISM OF SOLAR CELLS
Sunlight
Front electrode
N-type silicon
Load
P-N junction
P-type silicon
Back electrode
Current
Proton
Electron
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

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
Crystal silicon
Thin film silicon
Efficiency
13~17%
15%
Compound
Crystal silicon (in lab)
13%
More than 24%
FACTOR OF THE SOLAR CELLS EFFICIENCY

Spectral response
Transmittance
and
reflectivity of cover glass
Spectral response
CIS sensibility
Sunlight
Reflected light
Si sensibility
Cover glass
Transmitted light
Sunlight spectrum
Solar cell
Wave length (nm)
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
IMPROVE THE SOLAR CELLS EFFICIENT
Long wave length
Short wave length
Cover glass
Front electrode
Amorphous cell
Middle layer
Microcrystal Si cell
Back electrode
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

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
