Graphene
The theory of graphene was first explored by Wallace in 1947 as a starting point for understanding the electronic properties of 3D graphite. The emergent massless Dirac equation was first pointed out by Semenoff, DiVincenzo and Mele. The earliest TEM images of few-layer graphite were published by Ruess and Vogt in 1948. An early, detailed study on few-layer graphite dates to 1962 when Boehm and colleagues reported producing monolayer flakes of reduced graphene oxide. Efforts to make thin films of graphite by mechanical exfoliation started in 1990, but nothing thinner than 50 to 100 layers was produced before 2004. Initial attempts to make atomically thin graphitic films employed exfoliation techniques similar to the drawing method. Multilayer samples down to 10 nm in thickness were obtained.
Potential applications of graphene
In 2015, researchers developed a prototype cell that used semitransparent perovskite with graphene electrodes. The design allowed light to be absorbed from both sides. It offered efficiency of around 12 percent with estimated production costs of less than $0.06/watt. The graphene was coated with PEDOT:PSS conductive polymer (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate). Multilayering graphene via CVD created transparent electrodes reducing sheet resistance. Performance was further improved by increasing contact between the top electrodes and the hole transport layer.