Working Principle of a Semiconductor Based Solar Cell Excitation of - PowerPoint PPT Presentation

Working Principle of a Semiconductor Based Solar Cell Excitation of Charge Carriers II Week 2.3.2 Arno Smets

p-Doping B -

Energy band diagram of p-doped Silicon Thermal excitation Conduction Band Acceptor States E Fermi ` Valence Band

Typical Concentrations: 10 16 cm -3 Majority Carriers = 10 4 cm -3 Minority Carriers Si density in c-Si is 5  10 22 cm -3

Law of Mass Action n = electron carrier concentration } n . p=constant 1,21X10 20 cm -6 p = hole carrier concentration n = p = n intrinsic =1,1X10 10 cm -3 Intrinsic material n 0 p 0 = ( n intrinsic ) 2 Doping: At Room Temperature: p-type doping n-type doping n 0 = N D p 0 = N A ( n intrinsic ) 2 ( n intrinsic ) 2 p 0 = n 0 = n 0 p 0

Example n-type doping n-type doping example n 0 = N D = 10 16 cm -3 n 0 = N D ( n intrinsic ) 2 1,21X10 20 p 0 = p 0 = = 1,21X10 4 cm -3 n 0 10 16

Light Absorption scenario 1 E ph = E G :

Light Absorption scenario 2 E ph < E G :

Light Absorption scenario 3 E ph > E G :

Light Absorbtion in doped material before light absorption: 10 16 cm -3 Majority Carriers = 10 4 cm -3 Minority Carriers

Light Absorbtion in doped material 10 11 now electron-hole pairs : 10 16 + 10 11 cm -3 Majority Carriers = 10 4 + 10 11 cm -3 Minority Carriers

Light Doping P + F(E) Temperature - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 0,5 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - E - - - - - - - - - - - - - - - - - - - - - - - - - - E C E V E F

Thank you for your attention!