Key relationship
LED: eVgap≈hc/λ, I=max(0,V−Vgap)/R. Photodiode Iph=0.4 Popt. Solar guide I=Iph max(0,1−V/0.6).
Physics · Class 12
LED photodiode and solar cell
An LED converts forward electrical power to photons. A photodiode converts light to measurable current, commonly under reverse bias. A solar cell can deliver power to a load without an external bias source.
Open the interactive experiment →LED photodiode and solar cell
LED மின்சாரத்தை ஒளியாக மாற்றும். ஒளிமின்டையோடு ஒளியை மின்னோட்டமாக மாற்றும்; சூரிய மின்கலம் மின் ஆற்றலை வழங்கும்.
Key notes, relationships and model limits
Remember
An LED converts forward electrical power to photons. A photodiode converts light to measurable current, commonly under reverse bias. A solar cell can deliver power to a load without an external bias source.
Common trap
A photodiode’s reverse photocurrent sign is a current convention, not negative light intensity.
Model limits
Idealized LED20% electrical-to-optical conversion; detector responsivity0.4 A/W; solar IV is a linear0.6 V open-circuit guide. Temperature, spectral response and detailed diode physics omitted.
What you will learn
Compare emission, detection and energy harvesting.
Try the experiment
Try both scenarios, change one control, and predict the result before checking the graph and readouts.
Think of it this way
Change one input while keeping the others fixed, as you would in a controlled experiment.
Worked example
4 mW at0.4 A/W gives1.6 mA photo-generated current in the guide model.
Why this matters
The model connects led photodiode and solar cell with an observable reading. Check the equation and assumptions before applying it.
Before you start
SI units · algebra · graph reading
Check your understanding
Which device is intended to deliver electrical power from illumination?
- An unlit LED
- Solar cell
- A resistor alone
Read the explanation
A solar cell operates as a light-powered source.
Course connection: Class XII Chapter 14. Consult the roadmap for CBSE, NEET, JEE Main and Advanced scope.