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

Working Principle of a Semiconductor Based Solar Cell Semiconductor Junction II - The Solar Cell Week 2.4.2 Arno Smets

Semiconductor Junction – Thermal Equillibrium No net current - - - - + + + + - - - - + + + + p region n region - - - - + + + + + + + + - - - - + + + + - - - - Electron Diffusion J e = qD e dn/dx J e = nq  e E Electron Drift Hole Diffusion J h = qD h dp/dx J h = pq  h E Hole Drift

Semiconductor Junction – Forward Bias Field reduced - + - - - - + + + + - - - - + + + + p region n region - - - - + + + + + + + + - - - - + + + + - - - - Electron Diffusion J e = qD e dn/dx J e = nq  e E Electron Drift Hole Diffusion J h = qD h dp/dx J h = pq  h E Hole Drift

Semiconductor Junction – Forward Bias Field reduced Net - + current! - - - - + + + + - - - - + + + + p region n region - - - - + + + + + + + + - - - - + + + + - - - - Electron Diffusion J e = qD e dn/dx J e = nq  e E Electron Drift Hole Diffusion J h = qD h dp/dx J h = pq  h E Hole Drift

diffusion drift E F E F diffusion drift

diffusion drift E F E F diffusion drift

diffusion drift E F E F diffusion drift

diffusion drift E F qV E F diffusion drift

Semiconductor Junction – Reverse Bias Field increased - + - - - - + + + + - - - - + + + + p region n region - - - - + + + + + + + + - - - - + + + + - - - - Electron Diffusion J e = qD e dn/dx J e = nq  e E Electron Drift Hole Diffusion J h = qD h dp/dx J h = pq  h E Hole Drift

Semiconductor Junction – Reverse Bias Extremely Field increased - + Small Net current! - - - - + + + + - - - - + + + + p region n region - - - - + + + + + + + + - - - - + + + + - - - - Electron Diffusion J e = qD e dn/dx J e = nq  e E Electron Drift Hole Diffusion J h = qD h dp/dx J h = pq  h E Hole Drift

Semiconductor Junction – under illumination - - - - + + + + - - - - + + + + p region n region - - - - + + + + + + + + - - - - + + + + - - - - Electron Diffusion J e = qD e dn/dx J e = nq  e E Electron Drift Hole Diffusion J h = qD h dp/dx J h = pq  h E Hole Drift

Semiconductor Junction – under illumination - - - - + + + + - - - - + + + + p region n region - - - - + + + + + + + + - - - - + + + + - - - - Electron Diffusion J e = qD e dn/dx J e = nq  e E Electron Drift Hole Diffusion J h = qD h dp/dx J h = pq  h E Hole Drift

Short Circuit - - - - + + + + - - - - + + + + p region n region - - - - + + + + + + + + - - - - + + + + - - - -

Open Circuit V E Field - - - - + + + + - - - - + + + + p region n region - - - - + + + + + + + + - - - - + + + + - - - -

p-n junction Solar Cells Three essential steps required for the operation of a solar cell: 1. Generation of electron-hole pairs in the cell 2. Separation of electron and hole at the junction 3. Collection of electrons and holes at the terminals

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