40mA Solar Power from Transistor Core

I found this on Internet, and its very interesting, and nicely to share with others.

Simple DIY Solar Panel (Homemade)
Original Link :
https://circuitsdiy.com/simple-diy-solar-panel-homemade
https://rimstar.org/renewnrg/transistor_solar_cell_panel_calculator_2n3055.htm

This project isn’t something that uses a solar panel and uses the produced voltage for some electrical and electronics work. But this project shows how to make a solar panel yourself and what makes it reach maximum performance.

A solar panel is a photovoltaic cell where light energy is transformed into electrical energy.

Most photovoltaic cells are made of silicon chip above which there resides a very thin layer of noble metal through which around 1% of photon particles enter the material and activates electron flow.

Here I’m showing how to make one simple solar panel using transistor. The chosen transistor is 2N3055 in metallic TO-3 package. The below picture shows it’s image.

The small silicon chip inside the 2N3055 is able to produce photovolatge when exposed to sunlight and in the cell the emitter becomes the positive terminal and the collector becomes the negative terminal.





The current depends on the intensity of sunlight and the cell should produce more current if it gets more exposure.

Hence I used a magnifier convex lens (+10 diopter, 60mm diameter) and focused the point of sunlight into the silicon square, and the results were surprising.

The same cell produced near 0.65 volts which is 44% more voltage and produced 42.2mA current which is 210 times more than the previous one.

Logical explanation of the huge current increase:

The cell area is 2mmx2mm=4mm^2

When the lens focused the light to a 2mm diameter circle, the area of the circle was 2mmx2mmxpi/4=3.14mm^2. The lens was 60mm in diameter so it took sunlight of 60mmx60mmxpi/4=2826mm^2. So the silicon chip got 900 times more sunlight and produces the huge current.








Video materials:
https://www.youtube.com/watch?v=2bUc8RqSFXs
https://www.youtube.com/watch?v=tSxc5jbaAIU
https://www.youtube.com/watch?v=526xslmO6Ds
https://www.youtube.com/watch?v=xknEpEDsciw

Hey... you've invented the phototransistor!

Seriously, the effect you see is very common, even an LED with light shone on it produces a voltage. The problem is it produces very little power, I would guess you measured the 42.2mA under short circuit conditions with the meter straight across the 2N3055, in other words at almost zero voltage, to be useful you need to produce the current and 0.65V at the same time. You will find the voltage doesn't go above 0.65V because the junction starts to become forward biased and conducts it's own current away. Transistors were used like this back many years ago to receive modulated light beams, the voltage was fed to an audio amplifier then on to speakers.

Brian.

I dont think so that we can harvest that amount of energy from photodiode or phototransistor. Photodiode price is high in comparison with 2n3055, and phototransistors have small core. ;-)