Almost every electronic hobbyist has a pile of old or defective 2N3055's in his hobby schack. These transistors can be recycled to provide energy - solar energy.
A power transistor like 2N3055 can be used as a solar cell by cutting or sawing off its metal top,
exposing its silicon chip, and then placing it under the sun. Even a defective transistor can be used for this purpose as long as two of its terminals still create a diode junction.
A transistor used as a solar cell produces voltages up to 0.7V. However, this output voltage is dependent on the load current. The graph on the left shows the relation of its output voltage to the load current. This current output can be increased by using a non-defective transistor, and connecting its collector and emitter together in
parallel as shown in the diagram 15.1. To increase the voltage level, you can connect several such transistors in series. By joining them in parallel, you can increase the current output.
Output voltage to load current
Electronic Circuits volume 1.0 - Circuit Nr. 15
The complete data of the electronic circuit described above can be found in the following book and is available from Amazon.com.
Click on the image to view the book.