LED Solar cell and its working
Ever thought of using LED as a solar cell? Do this experiment to find that out how it works. In this article, I will tell about LEDs. Circuit configuration required is necessary to convert LEDs into solar panel. Read the article to know about LED solar cells, their configuration and applications.
Solar cells are used to convert sun light into electrical energy. LED is capable of doing the same.About Light Emitting Diode (LED)
An LED is a semiconductor optoelectronic device which emits a narrow bandwidth of visible or invisible radiations (light). LEDs operate on electroluminescence (emission of light from a semiconductor under the influence of an electric field).
Internal Structure of a typical LED
Working of LED
In any normal PN junction diode, when a recombination occurs, the energy produced at the junction is released in the form of heat. These radiations are invisible. Unlike a PN junction diode, semiconductor materials like GaAsP and GaP are used in case of LED. If these materials are used, then recombination at the junction results in production of photons. Thus, the junction can act as a source of light.
In the figure shown below, anode is given a more positive potential than the cathode. This makes P region more positive than the n region. This positive potential at P region repels holes to the n side and the negative potential at the n side repels electrons to the P side. So, holes and electrons recombine at the PN junction and this produces energy. In case of an LED, this energy will be released in form of photons. These photons escape through the window provided on the anode and hence, the LED acts as a light source.
Colours & constructions
Depending on the type of material used to make the PN junction, the wavelength of light produced varies. Different colours are produced for different materials used in the construction.
Amber - AllnGaP
Blue - GaN
Green - GaP
Yellow - GaAsP
Red - GaAsP
White - GaNHow LED works as a solar cell?
Red LEDs act as solar cells when irradiated by solar energy.
When solar light is allowed to fall through the window of an LED, the photons in the light which has wavelength equal to the band gap of LED penetrates deep into the PN junction. On absorbing energy from these photons, the electron hole bond at the PN junction breaks and result in accumulation of electrons in the n side and holes in the p side. So, p side will be more positive than n side. This makes anode positive and cathode negative. Hence, LED acts as a cell.LED solar panel
The voltage produced by a single red LED is around 0.7 to 1.3 volts but its output current is very low. So, a single LED cannot be used for powering any device. To increase its output current and voltage, we will use a combination of LEDs which are connected both in parallel and in series. The advantage of this is that the parallel combination increases current rating while the series combination increases voltage rating.
If the current output of a single LED is around 100uA, then 2 LEDs in parallel can produce 200uA. Similarly, if the voltage produced by a single LED is around 1.3 volts, then 2LEDs in series can produce 2.6 volts.
LED solar panel circuit diagram
Home-made LED solar panel capable of producing 12 V 50mA
If the number of LEDs in this circuit is increased, more volts and higher current rating can be obtained.Typical applications
1. They can be used to construct cheap solar cells.
2. They can be used for mobile phone charging.
3. They can power double voltage oscillators used for low power devices like mosquito repellents , calculators and digital watches. Advantages
1. The cost incurred is low. They are economical in use.
2. They are easily available.Disadvantages
1. If it is exposed to sunlight for long period, the LED can damage. In order to prevent this, high power LEDs can be used.
2. All the LEDs should face the sun at the same angle. This can be done by mounting all the LEDs on a common PCB.
3. Since the output current is low, for high power applications, more number of LEDs must be used but this makes the circuit bulky.
Read New inventions in Solar cells of Photo voltaic technology
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Hi Vineeth,
If using yellow led, does it have different output voltage? I am very interested about led as solar cell. I want to exchange opinions with you, can I know your email?