A pinboard by
Olukunle Olawole

Assistant Lecturer, Covenant University


Generation of electricity in graphene thermoelectronic solar energy converter

All over the world the role of energy cannot be undermined in the creation of viable, healthy and world class economy of a country. Energy has contributed immensely to the steady growth of the developed nations like United State, Germany, United Kingdom, China and the like of others. Lack of stable electricity is one of the factors that has crippled the economy of Africa because it was not given highest priority. Some countries in Africa are in slavery because all the revenues realize from their gross domestic product are being used to service debt. So, advanced countries are now investing greatly on a new technology that would provide stable and clean electricity apart from the coal and fossil fuel sources. Therefore, there is a need to diversify our sources of energy to eco-friendly one as to as to escape from economy recession, hardship and threat of conventional means of generating electricity in our nature given habitat. Graphene is a high temperature material which can stand temperature as high as 4600 K in vacuum. Even though its work function is high (4.6 eV) the thermionic emission current density at such temperature is very high. Graphene is a wonderful material whose work function can be engineered as desired. Kwon et al reported a chemical approach to reduce work function of graphene using K2CO3, Li2CO3, Rb2CO3, Cs2CO3. The work functions are reported to be 3.7 eV, 3.8 eV, 3.5 eV and 3.4 eV. Even though they did not report the high temperature tolerance of such alkali metal carbonate doped graphene, their works open a great promise for use of pure graphene and doped graphene as emitter (cathode) and collector (anode) in a solar thermionic energy converter. My work discusses the dynamics of solar energy conversion to electrical energy using thermionic energy converter with graphene as emitter and collector. I considered parabolic mirror concentrator to focus solar energy onto the emitter to achieve temperature around 4300 K. I, modelled Richardson-Dushman equation to achieve the theoretical calculations and the modelling show that efficiency as high as 55% can easily be achieved if space-charge problem can be reduced and the collector can be cooled to certain proper temperature. This type solar energy conversion would reduce the dependence on silicon solar panel and has great potential for future applications.


Silver nanowire percolation network soldered with graphene oxide at room temperature and its application for fully stretchable polymer light-emitting diodes.

Abstract: Transparent conductive electrodes with high surface conductivity, high transmittance in the visible wavelength range, and mechanical compliance are one of the major challenges in the fabrication of stretchable optoelectronic devices. We report the preparation of a transparent conductive electrode (TCE) based on a silver nanowire (AgNW) percolation network modified with graphene oxide (GO). The monatomic thickness, mechanical flexibility, and strong bonding with AgNWs enable the GO sheets to wrap around and solder the AgNW junctions and thus dramatically reduce the inter-nanowire contact resistance without heat treatment or high force pressing. The GO-soldered AgNW network has a figure-of-merit sheet resistance of 14 ohm/sq with 88% transmittance at 550 nm. Its storage stability is improved compared to a conventional high-temperature annealed AgNW network. The GO-soldered AgNW network on polyethylene terephthalate films was processed from solutions using a drawdown machine at room temperature. When bent to 4 mm radius, its sheet resistance was increased by only 2-3% after 12,000 bending cycles. GO solder can also improve the stretchability of the AgNW network. Composite TCE fabricated by inlaying a GO-soldered AgNW network in the surface layer of polyurethane acrylate films is stretchable, by greater than 100% linear strain without losing electrical conductivity. Fully stretchable white polymer light-emitting diodes (PLEDs) were fabricated for the first time, employing the stretchable TCE as both the anode and cathode. The PLED can survive after 100 stretching cycles between 0 and 40% strain and can be stretched up to 130% linear strain at room temperature.

Pub.: 30 Jan '14, Pinned: 31 Jul '17