A schematic of how this OPV is stacked to create better carrier efficiency. The arrows represent sunlight.
As you bask in the sun this summer, whether it’s poolside, lakeside, or oceanside, you’re exposed to a great amount of solar energy, as is everything else around you. According to NASA, the sun sends about 1.8 x 1017 Joules per second, or a gazillion tons of energy (and yes, gazillion is a real scientific figure). So how do we currently harness all this free, clean energy?
We use solar panels, or photovoltaic (PV) cells, such as those found on the roofs of houses, near street lights, and with speed cameras. Solar cells are also used on a smaller scale, like in your trusty desk calculator. So, how do PV cells work? Sunlight, also known as photons, hits PV cells and excites electrons, enables their flow, and creates an electrical current. UCF researchers have created a new type of PV that carries an electrical current more efficiently, compared to other products in the market. This breakthrough will bring solar cell technology off of the roof and possibly onto your backpack.
Most solar panels, such as the large arrays seen in a desert, are crystalline silicon (c-Si)-based and are expensive to produce. More recently, researchers have been able create organic (or thin-film), PV cells (OPVs) that are more cost-effective, environmentally friendly, lighter, and more flexible. Additionally, unlike c-Si-based PVs, OPVs do not require direct sunlight and can generate power for longer in the daytime. Because of all of these benefits, this technology’s potential is endless, including use in electronics and in fabrics, such as window curtains. Yet, in comparison to inorganic PVs, there are a couple of barriers to this technology taking off: reliability — they don’t last as long — and efficiency.
This new type of OPV created by UCF researchers tackles the lack of efficiency by improving its structure. OPVs are layered structures with electrodes, the anode and the cathode, at the top and bottom. This innovation has a new type of anode, which can carry an electrical charge more efficiently (the technical term is carrier extraction).
Within this particular OPV device, this anode is formed with nickel and indium doped tin oxide (Ni-ITO). Glass is the first layer, where sunlight enters. The next layer is the Ni-ITO material, which is then followed by the nickel oxide material layer (p-NiO). Then, layered over that is a bulk heterojunction OPV material layer, made of a polymer with a really long name — poly (3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM); or, more easily said — P3HT:PCBM BHJ. Then, layered over that is a conductor material layer, such as aluminum, cathode.
There are similar versions of this type of OPV created by UCF researchers, but the inclusion of nickel is what makes for a more efficient OPV. Said in a more scientific way, the work function of the Ni-ITO anode is boosted within a range of -5.0 eV to -5.4 eV (without the nickel doping, it’s around -4.4 eV to -4.7 eV), and hole extraction, transport, and collection are enhanced. When efficiency is boosted, then more sunlight can be transformed into energy that we can use on a daily basis.
This boost in OPV efficiency is a significant step in manufacturing OPVs on items such as windows, curtains, and backpacks. Soon, solar energy will be able to do more than give you a tan (or a sunburn), a pitcher of sun tea…or, a speeding ticket.
For this and other brilliant technologies available for licensing, check out the UCF Technology Locator.
Written by Deborah Beckwin
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