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

Internal structure of 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 - GaN

How LED works as a solar cell?


Red LEDs act as solar cells when irradiated by solar energy.

LED as solar cell

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

led solar cell circuit diagram

Home-made LED solar panel capable of producing 12 V 50mA

Home made LED solar panel

LED solar panel side view

Home made LED solar panel back view
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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Comments

Author: ihsan04 Aug 2014 Member Level: Bronze   Points : 0

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?

Guest Author: A.K.Das.28 Dec 2014

Well, I would like to construct one, for my self,and then confirm, OK,But however, I must congratulate the auther for, his brain wave.Thanks.

Guest Author: arun02 Apr 2015

How many LED are required to make a mobile charger. Please send me the circuit diagram with 5vd c1000mA. I need it for my mobile.

Guest Author: sampson22 Jun 2015

How many LED's should I put such that it will generate 12V?

Guest Author: Eddy21 Oct 2015

This just doesn't work. At least not at the voltage level described. I just tried about 4 different kinds of LEDs. All were about the same results. With a single LED reading V on my multimeter with my iphone light touching the LED I get about 1.3-1.6 Vs. With 2 in series I get about 3V after that things go down hill fast. Adding LEDs in series from that point forward decreases voltage instead of increasing.

Next I tried to measure current. I couldn't read any current on a very nice Fluke DMM. I tried using another LED as a load or a little mini filament light bulb that I use on my breadboard. No current registered.

So I said what the hell I will solder up a board like in the article. I made 8 rows series each with 7 LEDs in parallel. The most Voltage I could get was .6 Volts and still couldn't read any current draw when I attached a load.

I thought maybe the current output was super small so I tried tripping the gate of a very sensitive SCR. No luck.

I think the problem is that the LEDs are a super weak power source but an easier load. How does this circuit keep from just draining its self trying to power the LEDs? It is like a free energy machine it just doesn't work even with external energy (light) applied.

Guest Author: Sherri14 Jan 2016

The theory is good, one I've been working on but cannot solve. I'm guessing each LED needs it's own circuit so that it's not losing power trying to energize it's neighbor. Does anyone have a solution for that?

Guest Author: Tom31 Dec 2016

The rule which regulate the use of LED's are in play. The reason you cannot get much energy out is a simple one.

When you place the LED's in parallel you are increasing the AMPS. When you place them in series you are increasing the Volts.

An LED operates at 5VDC. Once you SERIES the LED's close to that 5VDC, THE next LED in that series tries to use the 5V that is being produced by the previous LED's in that series. Since the AMPERAGE is not enough to power the LED that is trying to use the energy being produced by the previous LED's, you don't see any light being produced.

The LED that is consuming the power is using up all the energy produced. Perhaps the solution would be to use something like a diode bridge to separate each LED so they can produce power individually and tie them all together at the end. You would need to have diodes at the end of each circuit to keep the inverse voltage from feeding back through.

This is not a very good set up and the cost would be high. Solar panels would be cheaper than this setup.

But I give you props for experimentation.

You would need an acre of these to power a house. LOL :)

Guest Author: Frd196312 Jun 2017

@ Eddy and Sherry: I think the solution to both of your problems is, as the author said, that the LEDs need to be at the same angle. This means that they are at the same angle from the light source. With the sun as a light source, being mounted flat is as close as you will get to be at the same angle, however, if using the light on your phone, mounting flat will not be sufficient to get the angle the same. In fact, the closer the light source, the worse the angle difference will be. When LEDs are receiving light from different angles, they will be producing different amounts of power. When connected to other LEDs, their power may be used up by another LED that is underpowered.

Guest Author: prince10105 Sep 2017

This things doesn't work I tried it with other colors of LED's but still doesn't work I tried it with red I wired it in series and parallel but still doesn't work I used the LED strip then it worked I got the minimum of 6 volts.It doesn't work on normal LED's only on LED strip!

Guest Author: lowclearance11 Sep 2017

I tried this before I read this article then searched for the topic. The Red LEDs I used produced slightly less voltage than the Green and Yellow ones. Smalled ones produced more than the larger 5mm ones. I have not tried the IR ones I have but may do that next. I tried 4 in series and 8 in series. I was able to achieve 12VDC at an unknown amperage. I was also able to produce two 6VDC series wired parallel on a breadboard, again at an unknown amperage. I am not, by any means, a professional and was able to figure this out quickly. Notes:
- Sunlight is really the best option for a light source. Nothing else seems to produce these results.
- If this can be done consistently with a higher-powered LED, sufficient amperage can be produced.

Guest Author: Tyler looney05 Jul 2019

In a mad max world situation could a large enough led solar panel be mounted to a car with a electric motor and solid state battery to survive the wasteland vs Petrol vehicle? Electric cars would be the best solution in such a world so kinda hoping it could work lol

Guest Author: Neroxcide017 Aug 2019

Use a regular diode to prevent v/curnt loss ,then to mini caps for allocation then to storage bank.

Guest Author: Matthew19 Dec 2020

Where are you getting LEDs cheap enough to make this cost-favorable compared to just buying a solar cell?



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