The Sun is an intense ball of nuclear energy that has immense power, enough to drive our solar system for another five billion years. Solar power is no longer a strange or futuristic concept and has implementation beyond a solar-powered quartz watch or a solar-powered pocket calculator over decades. Presently, it is a rapid growing and increasingly important renewable alternative for electricity generation. More application of solar power is leading to increasing growth of the solar cell market.
Energy Generating Cell
A solar cell, also known as photovoltaic (PV) cell, is composed of semiconductor material that has the potential to directly convert sunlight into electricity.
The operation of solar cells have three basic attributes:
- absorbing light that generate either electron-hole pairs or excitons,
- separation of opposite type charge carriers, and
- different extraction of those carriers to an external circuit.
When the semiconductor is put out to light, it absorbs the light energy and transfer it to the electrons. This energy make the electrons flow through the material and generate electrical current. This electrical current that is generated is drawn out through conductive metal junctions which are the grid-like lines on a solar cell, and can then be used to power homes and the rest of the electric grid.
Solar cells are often packed together to form larger units called solar modules, which are in turn bundled into even bigger units- solar panels. The efficiency of a PV cell is simply a comparison of the energy taken from the light shining on it and the amount of electrical power coming out of the cell, which indicates how effective the cell is at converting energy from one form to the other. The amount of electricity generated from PV cells is dependent on the characteristics of the light (such as intensity and wavelengths) available and several properties of the cell. The bandgap is an important property of PV cells. This indicates what wavelength of light the material can absorb and convert to electrical energy. If the bandgap of the semiconductor matches the wavelength of light radiating on the PV cell, then that cell can efficiently make use of all the available energy.
In the 1960s, the research and development for photovoltaics began from the space industry where it required a power supply separate from the grid power for satellite applications. These space solar cells were highly expensive than what they are today. The need for an electricity generation method apart from grid power was still a decade away then, but solar cells became an interesting scientific variant to the rapidly expanding silicon transistor development.
The Greenhouse Effect
A significant benefit of photovoltaics is that PV is one of the most environmentally benign sources electricity generation. The effect on environment due to electricity generation, specifically the greenhouse effect, adds an important reason for implementing photovoltaics.
The Earth’s temperature is an equilibrium between the radiation coming from the sun and the energy radiated by the Earth into space. The outgoing radiation is strongly affected by the Earth’s atmosphere. If there had been no atmosphere, the average temperature on the Earth’s surface would be about -18°C. However, the natural level of carbon dioxide in the atmosphere absorbs outgoing radiation, hence containing this energy in the atmosphere and keeping the Earth warm.
Human activities are increasingly releasing gases, particularly carbon dioxide, ozone, nitrous oxides and chlorofluorocarbons (CFC’s), which prevent the normal escape of energy and potentially lead to an increase in Earth temperature.
Solar Cell Materials
The most commonly used semiconductor material in solar cells is silicon. It represents approximately 95% of the solar cell modules in the market today. Silicon solar cells observe a combination of high efficiency, low cost, and long life. Silicon atoms connected to one another to form a crystal lattice which provides an organized structure to make conversion of light into electricity more efficient.
A thin-film PV cell is made by settling of one or more thin layers of PV material on a material, such as glass, plastic, or metal, to support. There are two main types of thin-film PV semiconductors in the market today are cadmium telluride (CdTe), which is the next most common PV material after silicon owing to low-cost manufacturing processes, and copper indium gallium selenide (CIGS), that have optimal properties of PV material and high efficiency but the complexity involved in combining four elements makes the transition from lab to manufacturing more challenging. Both materials can be set directly onto either the front or back of the module surface and require more protection than silicon to enable long-lasting operation outdoors. Perovskite solar cells are a type of thin-film cell which are built with layers of materials that are printed, coated, or vacuum-deposited onto an underlying support layer, known as the substrate. They are typically easy to assemble and have similar efficiency to that of silicon cells.
Organic PV (OPV) cell are possessed with organic (carbon-rich) compounds that can be tailored to enhance a specific function of the PV cell, such as bandgap, transparency, or color. They have short lifetimes and are current half as efficient as silicon cells.
Quantum dot solar cells generate electricity through small particles of different materials of semiconductor that are just a few nanometers wide. It is difficult to create an electrical connection between them, so they’re not very efficient.
Even though generating power from the sun is without cost, the technology behind this process is not. Numerous policies and incentives offered by various governments to support the use of solar energy are expected to open new prospects for the industry. Several schemes, such as tax benefits, subsidy, net metering, financial assistance, low import duty, and feed in tariff, have started to be implemented by governments to encourage industry growth. These factors are driving the solar cell market.