Solar cells have always relied on the metal indium, due to its transparency, which is essential to light emission or absorption in electronics. Engineers also regard indium valuable in LCDs and other transparent electrical devices. However, indium is a relatively rare metal on Earth and existing supplies are rapidly dwindling. Researchers have frantically searched for transparent conducting materials to little avail.
A new team claims it may have found the solution in one of the Earth's most abundant elements. Researchers at the Planck Institute have devised a new approach, utilizing graphene -- single 2D layers of carbon atoms, extracted from graphite -- 10 layers of which are applied to form an electrode. Each layer that comprises the electrode is a mere 5 nm thick.
The material has conductivity comparable or superior to indium and falls just slightly short of indium in transparent character. The current device is 80% transparent to visible light and 100% transparent to infrared light.
The team constructed a prototype using a process that will be drastically changed and refined. The prototype used graphite oxide flakes which were applied to form layers of surface coating between 10 nm to 100 nm thick. The coating was then heated to remove the oxygen, leaving behind a simple graphene-like material.
Assuming a better production process can be devised, mass produced
solar cells made cheaply and with even better efficiency. The superior absorption of IR radiation would allow these cells to possibly surpass the production of traditional indium cells by capturing more of the EM spectrum. The team stated that they strongly believe that visible light efficiencies of 90 percent or higher are achievable.
The biggest challenge is that the formation of graphene is difficult and often leaves "creases" of extra carbon atoms. These creases distort light and lower the transparency. A sheet of perfect graphene would have nearly 100% transparency across the EM spectrum, including visible light. One positive, though is that the material is exceptionally stable and resistant to heat and acid, making processing much more viable.
While this discovery is likely 5 to 10 years from seeing serious production, it holds great promise to both provide unprecedented clean power and to provide a viable solution for electronics displays. With the inevitable depletion of indium, this may be one process that is forced to move from theory to mass production at an accelerated rate.