The photodiode solar cell and Zener diode

Let’s take a look at the diode, which is the most common two-terminal electronic device. Diodes are two-terminal electrical components that are designed to conduct electricity in just one way. They are small and inexpensive. There are many different types of diodes accessible, including the Light-Emitting Diode (LED), the Laser diode, the Avalanche diode, the Zener diode, the Schottky diode, the Photodiode, and the PN junction diode, among others.

P-N junction diodes are also referred to as rectifier diodes in some circles. P-N junction diodes are composed of two layers, with one layer doped with P-type semiconductor material and the other layer doped with N-type semiconductor material. P-N junction diodes are used in the production of lasers. The P-N junction is formed when two P-type layers are combined with an N-type layer to make a single junction. As a result, the junction diode is referred to as a P-N junction diode.

Let’s take a closer look at the P-N junction diodes that are used for specific applications.

1. Zener Diode

2. Light-Emitting Diode

3. Photodiode

4. A solar cell or photovoltaic devices

Optoelectronic junction devices include light-emitting diodes, photodiodes, and photovoltaic devices, all of which are types of light-emitting diodes.

The Zener Diode 

The zener diode is a type of semiconductor diode that is unique in that it permits current to flow in the opposite direction of the current. It is a one-of-a-kind diode that is engineered to conduct in the opposite direction when a particular specified voltage is attained, making it a unique device. Clarence Melvin Zener is credited with being the first person to describe the electrical properties of the Zener diode.

The Zener diode has a p-n junction that is extensively doped, which permits current to flow in either the forward or backward direction. Knee voltage and zener voltage are both terms used to describe the same thing. It is the voltage that is adequate to cause the reverse breakdown state that allows the diode to conduct in the opposite direction of its normal operation. The Zener Effect is a form of electrical breakdown that occurs when the Zener diode is Reverse-biassed

Symbol for the Zener Diode

A Zener diode behaves in the same way as a conventional diode when the current is directed forward. An insignificant leakage current is generated and circulated throughout the device under reverse biassed conditions. When the reverse voltage rises to the determined  breakdown voltage (Vz), the current starts to flow through the diode and it is turned on.

There are two sorts of breakdowns that can occur in a Zener Diode:

1. Avalanche Breakdown

2. Zener Breakdown

When a sufficiently enough reverse voltage is applied to a Zener diode or a rectifier, the avalanche breakdown phenomenon occurs. Zener breakdown happens at low reverse voltages,

The V-I characteristics are explained in greater detail in the following figure. An explanation of the V-I properties of a Zener diode is presented in two stages:

(i) Forward Characteristics

(ii) Reverse Characteristics

V-I Zener Diode Characteristics

The term “light-emitting diode” refers to a semiconductor that emits light (LED)

Light-emitting diodes are electronic components that emit light when an electric current flows through them. The Light-Emitting Diode (LED) is a specific form of diode with features that are comparable to those of the p-n junction diode. When energy passes through the LED, the electrons recombine with the holes in the device, resulting in the emission of light.

The diode is represented by the symbol displayed below. The diode is protected by a transparent cover that allows you to see the light it emits. 

Light Emitting Diode

When the LED is forward biassed, electrons move from the N-type to the P-type of the semiconductor. Holes are transferred from the p layer to the n layer. At the boundary, the concentration of minority carriers grows as a result of the forward bias that exists. A recombination of majority carriers and surplus minority carriers occurs at the junction. Whenever the minority carriers recombine with the majority carriers, energy in the form of photons is liberated from the system. Emitted photons have energies that are less than or equal to the bandgap. When the current reaches its maximum value, the intensity of the light increases.

LEDs have V-I properties, which means they can emit light in the colours red, green, orange, yellow, and blue. Light-emitting diodes (LEDs) consume less energy than other types of lighting. They become acclimated to the capacity to switch instantly on and off. They are both cost-effective and long-lasting in their performance.

Photodiodes

Photodiodes are a unique type of p-n junction diode that operates with a reverse bias voltage. They are primarily intended for use in the detection of optical signals. Photodiodes are constructed with a clear window that allows light to pass through them. Photodiodes are also referred to by a number of different names, including light detector, photodetector, and photo-sensor. Some of the photodiode materials are silicon, germanium, indium gallium arsenide, to name a few. 

Photodiodes are formed of photosensitive semiconducting material, which absorbs the light that shines on them and emits it back into the environment. Photodiodes are operated under reverse bias circumstances that are below the breakdown voltage of the semiconductor.

It is possible for electron-hole pairs to be formed at the depletion area when the energy of the photons striking the photodiode (hv) is greater than the energy gap (Eg) of the semiconductor material in the photodiode.

In the presence of an electric field, electrons and holes are separated before they can unite and form atoms. When an electric current flows through it, electrons collect on the n-side and holes accumulate on the p-side of the semiconductor. When electrons and holes travel about in the photodiode, an electromagnetic field is formed. When an external load is connected to the gadget, current flows through it. The photocurrent created has a magnitude that is directly proportional to the intensity of the light that is incident on it.

Under reverse bias conditions, the current increases in proportion to the increase in light intensity (or vice versa). Photodiodes are utilised in a variety of applications, including logic circuits, solar cell panels, detecting circuits, character recognition circuits, and optical communication systems, among others. 

Solar Cell

Solar cells are also referred to as photovoltaic cells in some circles. Photovoltaic (or solar) cells are electrical devices that use the photovoltaic effect to convert visual radiation into electricity. 

Solar power, often known as solar energy, is the primary source of energy for numerous devices, including solar cookers, water heaters, lamps, and other similar equipment. Inform us about the operation of the solar cell, which is a critical component.

Several layers of semiconductors are used in the construction of solar cells. Two layers of charge are present: one layer is positive, while the other layer is negatively charged. As we all know, sunshine is composed of small packets of energy known as photons that travel through space. When sunlight strikes a cell, pictures are either transmitted, reflected, or absorbed depending on their wavelength.

A three-step procedure is followed in this case:

Generation, Separation & Collection.

When photons are absorbed by a layer containing negative charges, the energy of the photon is transferred to an electron in an atom of the cell, resulting in the cell being powered. When the energy of the electrons increases, they are able to escape to the outer shell of the atom. By creating a potential difference between the positive and negative layers, the released electron can migrate to the positive layer and therefore to the positive layer. An external circuit is formed when the two layers of material are joined together, and an electron is allowed to flow across the circuit, resulting in a current.

Solar cells as Renewable Energy 

Solar cells are renewable solar energy sources that do not pollute the environment. They are also environmentally friendly. Solar cells require nothing in the way of maintenance and repair. They are cost-effective and may be deployed virtually anywhere.

Conclusion

In electrical circuits, a p-n junction diode is a fundamental semiconductor device that regulates the passage of electric current. Adding impurities to each side of a silicon semiconductor creates a positive (p) and a negative (n) side, which is what makes it a semiconductor. p-n junction diodes are represented as a triangle with one point directed toward a line.