Working Principle of a Semiconductor Based Solar Cell 3.1 Solar Cell - PowerPoint PPT Presentation

Working Principle of a Semiconductor Based Solar Cell 3.1 Solar Cell Operation Week 3 Arno Smets

Equivalent Circuit JV ‐ Curve V mp 10 10 Current Density (mAcm ‐ 2 ) R Power Density (mWcm ‐ 2 ) 0 0 I s V oc I D I SH + ‐ 10 ‐ 10 P max I PH R SH V ‐ 20 ‐ 20 _ J mp J sc 30 30 ‐ 40 ‐ 40 ‐ 0.2 0.0 0.2 0.4 0.6 0.8 1.0 Voltage (V) Maximum power point

pn Junction p ‐ doped n ‐ doped ‐ ‐ ‐ ‐ + + + + ‐ ‐ ‐ ‐ + + + + ‐ ‐ ‐ ‐ + + + +

Transport of Charge Carriers E ‐ Field

pn Junction E ‐ Field - - - - + + + + - - - - + + + + p region n region - - - - + + + + + + + + - - - - + + + + - - - -

pn Junction ‐ Reverse bias in the dark Field increased + - - - - - + + + + - - - - + + + + p region n region - - - - + + + + + + + + - - - - + + + + - - - -

pn Junction ‐ Forward bias in the dark Field reduced + - Net current! - - - - + + + + - - - - + + + + p region n region - - - - + + + + + + + + - - - - + + + + - - - -

pn Junction – Under illumination E ‐ Field - - - - + + + + - - - - + + + + p region n region - - - - + + + + + + + + - - - - + + + + - - - -

Equivalent circuit of solar cell The dark current of the p ‐ n junction I D V

Equivalent circuit of solar cell ‐ Reverse bias The dark current of the p ‐ n junction I I D Extemely small net V current!

Equivalent circuit of solar cell ‐ Forward bias The dark current of the p ‐ n junction I I D Extemely small net V current!

Reverse Bias Forward Bias 10 Current Density (mAcm ‐ 2 ) 0 ‐ 10 ‐ 20 ‐ 30 ‐ 40 ‐ 0.2 0.0 0.2 0.4 0.6 0.8 1.0 Voltage (V)

Reverse Bias Forward Bias 10 Current Density (mAcm ‐ 2 ) 0 ‐ 10 - - - - + + + + ‐ 20 - - - - + + + + - + - - - - + + + + - - - - + + + + ‐ 30 - - - - + + + + ‐ 40 ‐ 0.2 0.0 0.2 0.4 0.6 0.8 1.0 Voltage (V)

Reverse Bias Forward Bias 10 Current Density (mAcm ‐ 2 ) 0 ‐ 10 - - - - + + + + ‐ 20 - - - - + + + + + - - - - - + + + + - - - - + + + + ‐ 30 - - - - + + + + ‐ 40 ‐ 0.2 0.0 0.2 0.4 0.6 0.8 1.0 Voltage (V)

Reverse Bias Forward Bias 10 Current Density (mAcm ‐ 2 ) 0 ‐ 10     I  I DARK  I 0 exp qV      1  ‐ 20     k B T   30 ‐ 40 ‐ 0.2 0.0 0.2 0.4 0.6 0.8 1.0 Voltage (V)

Reverse Bias Forward Bias 10 Current Density (mAcm ‐ 2 ) 0 ‐ 10    I 0 I  I DARK  I 0 0  1 ‐ 20 ‐ 30 ‐ 40 ‐ 0.2 0.0 0.2 0.4 0.6 0.8 1.0 Voltage (V)

Reverse Bias Forward Bias 10 Current Density (mAcm ‐ 2 ) 0 ‐ 10     I  I DARK  I 0 exp qV      1  ‐ 20     k B T   ‐ 30 ‐ 40 ‐ 0.2 0.0 0.2 0.4 0.6 0.8 1.0 Voltage (V)

Reverse Bias Forward Bias 10 Current Density (mAcm ‐ 2 ) 0 ‐ 10   I  I DARK  I 0 exp qV     ‐ 20   k B T ‐ 30 ‐ 40 ‐ 0.2 0.0 0.2 0.4 0.6 0.8 1.0 Voltage (V)

Equivalent circuit of solar cell The illuminated ideal p ‐ n junction I I D + I PH V _

10 Current Density (mAcm ‐ 2 ) 0 drift currents ‐ 10 light induced minority carriers ‐ 20 ‐ 30 ‐ 40 ‐ 0.2 0.0 0.2 0.4 0.6 0.8 1.0 Voltage (V)

10 Current Density (mAcm ‐ 2 ) 0 - - - - + + + + ‐ 10 + + + - - - - + - - - - + + + + ‐ 20 + + + - - - - + + + + - - - - + 30 ‐ 40 ‐ 0.2 0.0 0.2 0.4 0.6 0.8 1.0 Voltage (V)

10 Current Density (mAcm ‐ 2 ) 0 I  I PH  I DARK  J  I ‐ 10      I PH  I 0 exp qV      1 ‐ 20    A   k B T   30 ‐ 40 ‐ 0.2 0.0 0.2 0.4 0.6 0.8 1.0 Voltage (V)

10 Current Density (mAcm ‐ 2 ) 0 J  J PH  J DARK  J  I ‐ 10      J PH  J 0 exp qV      1 ‐ 20    A  k B T    ‐ 30 ‐ 40 ‐ 0.2 0.0 0.2 0.4 0.6 0.8 1.0 Voltage (V)

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