Arno Smets

Solar Cell OperationDesign Rules: utilization of band gap energy

Week  3.4

2. Spectral Utilization

Design Rules Solar Cells

1. Band Gap Utilization

3. Light Trapping

Delicate Interplay

2. Spectral Utilization

Design Rules Solar Cells

1. Band Gap Utilization

3. Light Trapping

Delicate Interplay

2. Spectral Utilization

Design Rules Solar Cells

1. Band Gap Utilization

3. Light Trapping

Delicate Interplay

2. Spectral Utilization

Design Rules Solar Cells

1. Band Gap Utilization

3. Light Trapping

Delicate Interplay

p

n

EFn

EFp

qVoc

Band gap utilization

1ln

0JJ

qTkV PHB

OC

p

n

EFn

EFp

qVoc

Band gap utilization

1ln

0JJ

qTkV PHB

OC

Voc 2kT

qln

GL0

ni

Charge Carrier Recombination

Radiative Auger SRH

Charge Carrier Recombination

Shockley Read Hall1

0 tN

Voc 2kT

qln

GL0

ni

Charge Carrier Recombination

Radiative Auger SRH

Charge Carrier Recombination

Relectron

kn2p e ,Aug

pR 1kn2

Rhole

kp2n h,Aug

nR 1kp2

Charge Carrier Recombination

Relectron

kn2p e ,Aug

pR 1kn2

Rhole

kp2n h,Aug

nR 1kp2

Charge Carrier Recombination

Momentum

Energy

Indirect band gap

photonphonon

Momentum

Energy

Direct band gap

photon

Momentum

Energy

Indirect band gap: c‐Si

photonphonon

Momentum

Energy

Direct band gap: GaAs

photon

Band gap utilization:  .....the Voc is limited by

Radiative Auger SRH

Defect‐rich absorber layer

Band gap utilization:  .....the Voc is limited by

Radiative Auger SRH

Defect‐free indirect band gap 

Band gap utilization:  .....the Voc is limited by

Radiative Auger SRH

Defect‐free direct band gap

Diffusion Length

Diffusion length:

p‐doped

Le De e Lh ehhh LDL

n‐doped

---

- - -- - -- - -

+ + + +

+ + + +

+ + + +

Minority carrier diffusion length

Ld

Relation between diffusion length and typical thickness of solar cells

Ld

p

n

EFn

EFp

qVoc