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As the world tries to reduce the use of fossil fuels and instead rely on greener, more green energy, more efforts are focused on improving the existing renewable technology and developing devices that make use of the renewable sources of energy in innovative ways. Solar cells capture sunlight and is being touted as one of the best popular green energy resources. But, there are many different ways that sunlight can be utilized to create energy.
With the amount of sunlight that strikes the Earth every daily, it is an a huge opportunity for solar-powered energy harvesting devices to be one of the leaders for a greener and cleaner society. They can also expand their status among the top renewable technologies. Designers are testing and utilizing 2D materials in a variety of these solar harvesting systems including the widespread use of graphene in solar cells , to the application of different 2D materials in photocatalytic as well as photothermal harvesting techniques.
Photovoltaics (Solar Cells)
Of all the solar harvesting methods and methods available solar cells are one of the best-known, widely used, and efficient option. There are numerous bulk solar cells that are made of perovskite and silicon materials. Furthermore, a range of new approaches are being created in which 2D substances (and various other types of nanomaterials) are used to enhance the performance of silicon bulk solar cells or provide an opportunity to make smaller and better-performing solar cells. In the former we have several flexible organic solar cells However, active materials typically have less performance than organic materials, and therefore 2D materials are a means to make solar cells thinner that have a much higher performance.
Numerous devices exist where doped graphene is used as a photoactive substance in the semiconducting junction of photovoltaics within solar cells. Sometimes alone, and sometimes when it is used in conjunction with silicon to create larger solar cells. In addition graphene, as well as its derivatives have been marketed as a possible alternative to holes in the transport layer, instead of costly noble metals such as gold and silver as a way to reduce the cost of solar cells that are large scale. Graphene is also utilized in combination with silicon in a variety of hybrid devices, for instance, in the creation of thinner flexible , semi-transparent solar cells.
Although graphene has garnered the most attention graphene and the transition metal diacogenides (TMDCs) are currently being incorporated into various solar cells due to their durability and resistance to various degrading factors–to enhance their stability over time and ensure that they operate at their peak for a longer period of time. These two-dimensional materials are used in a variety of solar cells that are bulk on commercial scale, such as in perovskite and silicon cells, as well as the tandem cells.
In recent times, the fascination for the development of flexible solar cells expanded, and even though graphene was the initial 2D solar cells, the field has grown and continues to expand. In recent times, TMDCs have been used in conjunction with graphene to produce energy efficient solar cells that are flexible and perovskite material is currently being developed into 2D sheets in order to attempt to replicate the performance of the larger perovskite solar cells, but in the form of a smaller, more versatile solar cell. 2D perovskite solar cell haven’t yet reached the dimensions of their larger counterparts, however it is an entirely new component of the 2D family, which means there’s plenty of time to make an appearance in 2D solar cells that are enhanced with materials.
Photocatalytic Harvesting
Photocatalytic reactions create new, greener fuels. They are distinct from other techniques for harvesting energy that produce direct electricity. In photocatalytic harvesting, energy that sunlight produces is used to generate fuel that is then used to power electronic devices and systems. Photocatalytic harvesting is an intriguing option for water splitting technology to create hydrogen fuel.
Photocatalytic harvesting is a process that occurs when semiconducting materials are utilized. The photocatalytic harvesting takes place because photons emitted by the sun (with the highest energy) create an electron-hole pair within the semiconducting materials once they are absorbed. But, these photogenerated excited states are unstable, which is why the charge carriers combine. As a result of the process of separation and recombination electrons and holes move through the surfaces of the materials that either reduces or even transforms the atoms that are absorbed. This process generates hydrogen gas. Additionally, there is a similar process of photocatalysis which can be utilized to create oxygen molecules, too (often simultaneously).
Photocatalytic reactions can be started by using a variety of materials. A range of semiconducting materials are utilized for Photocatalytic Harvesting Reactions. In many instances the edges exposed of the 2D sheets provide a suitable place for photocatalytic processes to occur. TMDCs like molybdenum dioxide, have garnered lots of attention since they actively absorb hydrogen ions. Graphene or its derivatives including doped versions that create semiconducting materials and tested, are also highly-tested due to the large surface area of graphene as well as TMDCs in addition to their absorption capabilities and electrical conductivity characteristics, make them ideal catalysts to conduct hydrogen evolution reactions (HER) to create hydrogen fuel.
Photothermal Harvesting
The photothermal harvesting techniques offer a different perspective to traditional solar harvesting techniques. These harvesting techniques photothermal materials are utilized for absorbing light and transform the energy into heat. 2D materials possess a variety of optical properties which can be harnessed to absorb light waves, and then transform it into heat. Some materials 2D materials having special optical properties and not seen in other materials classes and others with advantageous properties overall.
2D materials are known for their ability to absorb electromagnetic radiation in a variety of wavelengths across a broad spectrum including near- and visible regions. But, the applications differ in the sense that they are generally employed in medical settings that allow various procedures to be carried out. The absorbtion of light and the generation of heat implies that various medical procedures can be carried out without the need for more aggressive methods. For instance, heat is produced in the form of an energy vibration, which can then be utilized to target and destroy cancerous cells.
It’s a method that’s more specialized in nature although it doesn’t provide power to devices, various 2D materials ranging from graphene derivatives to TMDCs, MXenes and TMDCs are utilized to capture light for innovative and effective medical treatments. In addition, photothermal treatments are now an exciting applications area for 2D materials in addition to the more traditional methods of harvesting solar energy.
Conclusion
Solar harvesting, which is in the form by solar cells an established technology. However, 2D materials provide ways to increase the efficiency and long-term stability of solar cells while also developing new methods to create thin, flexible as well as clear solar cells. In addition to solar cells, these 2D material offers an excellent opportunity to create hydrogen fuel using photocatalytic reactions, as well as harvesting light to aid in advanced cancer treatments. As our society seeks the possibility of capturing more energy from our natural resources 2D materials are the possibility of converting sunlight into useful output that is efficient and usable.
