Photodiode vs. Solar Cell: Key Differences Explained

This article compares photodiodes and solar cells, highlighting their differences. This is a common question asked during physics practical exams, especially at the Class 12 level.

Introduction

Both photodiodes and solar cells are photovoltaic semiconductor devices. They both utilize light as input and generate respective outputs based on their intended application. Essentially, they are both optoelectronic junction devices.

Photodiode

• A photodiode is a p-n junction diode designed to allow light to fall upon it through a transparent window.
• When illuminated with light energy (hv) greater than the energy gap (Eg), it generates electron-hole pairs due to photon absorption. These electron-hole pairs are generated near the depletion region of the photodiode.
• It generates current through an external load when reverse biased.
• The magnitude of the generated photocurrent depends on the incident light intensity.
• Photodiodes find uses in cameras, CAT scanners, smoke detectors, barcode scanners, fiber optic links, and more.

Solar Cell

• A solar cell is a p-n junction device that generates electromotive force (EMF) when light radiation falls on its junction. The photon energy of the light should be greater than the band gap.
• It doesn’t require an external bias for its operation.
• Solar cells are used to produce more power, so their junction area is typically larger.
• Semiconductor materials with band gaps close to 1.5eV are often used in solar cell manufacturing. Materials with higher optical absorption and high electrical conductivity are chosen for fabrication.
• Solar cells are commonly used in satellites, space vehicles, calculators, and as backup power sources in homes.

Difference Between Photodiode and Solar Cell

The following table summarizes the differences between photodiodes and solar cells based on various parameters:

I-V Characteristics