SinodosChemistry

Graphene has been characterized as a ‘miracle’ material since its discovery due to its unique mechanical and electrical properties. Graphene exhibits superb strength, electrical conductivity and transparency; all of these properties can be modified and tailored to our needs via doping and chemical modification of graphene’s structure. Graphene’s structure is becoming a ‘bible’ for scientists in the chemical, electrical and optics industry. Graphene is a two dimensional carbon sheet that contains hexagonal rings. Its numerous applications and its size dependent properties have led to a variety of applications in electronics, sensors, composites, plastics and other manufacturing sectors. One of the most important and most prominent sectors however is the solar panel based energy generation.

Solar panels based energy generation technology is widely known up to date; photons from the solar radiation fall onto a semiconductor and excite the same number of electrons [this is the case except for specific variations that allow for multi electron excitement]. These electrons are then ‘captured’ and an electric current is generated. In order for this process to successfully occur various material and design properties have to be achieved; a semiconducting material that can easily provide excited electrons, a transparent receptor that allows for the light to pass onto the semiconductor and be trapped there and high efficiency pathways for the electrons to maintain a high generation efficiency. The whole process has been based mostly on silica, inorganic and organic solar panels for the last two decades. Silica based solar panels are categorized into monocrystalline and polycrystalline with the first being more efficient [15-20% conversion vs 13-16%], more expensive, and more enduring than the second one. On the other hand, Thin film solar cells utilize silica, inorganics [such as Cadmium Telluride, Copper Indium Gallium Selinide and others] as well as organics for their manufacturing and have achieved efficiencies up to 13% conversion but al low manufacturing effort.

Graphene offers a revolution era for solar panel applications as at least five different approaches have been identified so far that greatly promote the efficiency of today’s solar technology. The first approach that is under investigation is the direct use of Graphene in the different classes of solar panels as the semiconductor and transporting materials. Although graphene demonstrates an amazing conductivity, its electron species transportation within the photovoltaic cell is not ideal. For this reason, combinations of Graphene [and most importantly modified or doped Graphene] with other organics and inorganics are currently under investigation. This approach is expected to offer a medium increase in solar panels efficiency and in combination with efforts and ideas that follow is expected to boost worldwide production of solar energy.

 

 

The most recent advance however is the idea of generating electricity in graphene based solar panels even when it rains. Such a construction would allow for worldwide generation of clean, renewable, infinite energy at larger generation rhythm, and at larger time periods. This technology would allow even for countries away from the equator to invest in solar panels technology; this in turn would lead to even lower prices of electricity and minimization of CO₂ emissions. The idea as presented by the pioneers in the field is quite simple: rain contains a variable amount of salts and these salts are found in the form of anions and cations in the rain droplets. Graphene ultra thin films are used to separate the anions from the cations by binding the cations on the graphene surface. Via this process a double layer is formed which is termed a pseudo capacitor. The potential difference between the two layers of the capacitors leads to the electric current generation that adds to the overall efficiency of the solar panel. Although this design is in its initial stage, its importance is vital; should this type of graphene solar panels be successfully realized, solar energy generation will change every other related field in the world, from industrial and manufacturing activities to residential applications.

Swiss researchers have initiated another field of investigation of graphene based solar cells that may prove to be the decisive one in our efforts to achieve complete energy sustainability. The research group employed trARPES (ultrafast time and angle resolved photoemission spectroscopy) to study the electron excitement process in graphene and in a number of doped forms of graphene. What they confirmed is that doped forms were able to excite their excess electrons under photon falling on the nanomaterial. Using the doped graphene structures they were able to excite two electrons for each falling photon, thus doubling the theoretical maximum of solar energy conversion efficiency. This maximum is currently accepted to be found in the narrow range around 32%; however should the multiple excitement technology be proved viable the new theoretical maximum of solar conversion could be around 64%. This advance alone could solve the energy and pollution control problem around the world. This investigation is also on going; further advances that could lead to even higher ratios of excited electrons per falling photons should not be excluded from our expectations.

A recent finding suggested another way to optimize graphene for solar panel applications; researchers have accidentally witnessed the interactions of soda lime glass with graphene structures. When attaching thin layers of graphene and soda lime glass, soda penetrates graphene and dopes it in an optimal way. Investigations have shown that this unforeseen and very cheap combination leads to a high efficiency, optimally prepared in terms of electron density graphene that can be employed for solar panel applications and multiple excitements of electrons.

One last approach that is very prominent for solar energy generation is the use of graphene quantum dots. Quantum dots exhibit electronic properties that are size dependent and have been investigated for a decade now. The new use however has just been identified by a Saudi-Arabia based research team. Graphene quantum dots have been successfully used for down conversion of solar light that is to transform high energy light to low energy light (different range in the light spectrum). Down conversion of light allows for great increases in solar panels’ conversions; silica is a very efficient converter of light to electrons when the light is found in the visible range. However, when the light is of higher energy (in a higher spectrum region) silica is a very poor converter. Graphene quantum dots offer a great breakthrough for the existing silica based solar panels.

Graphene is expected to provide advances and working prototypes for all the above investigations. Solar energy generation is expected to grow significantly due to graphene and graphene doped and modified forms in the near future. The new electricity generation capabilities will change the world economy as we know it.