Semi-conductor solar cells

The aryl-aryl bond formation is the most important reaction in the synthesis of various polyaryl materials which possess valuable conducting properties. The polyaryls such as poly-p-phenylene (PPP), which by various doping procedures reach a conductive state, are in focus as a potential for use as electrode materials in light-weight rechargeable batteries, electrochemical cells, semi-conductor devices, solar cells, and in the several other possible electrochemical uses. Very comprehensive polyarene-chemistry and its practical applications are excellently rewieved by Takakazu Yamamoto [6]. 

As a result of these factors, the universal paradigm for inorganic solar cells, the p-n junction, cannot be adapted for organic semiconductors. The contrast with inorganic semiconductors is shown schematically in Fig. 7.2. The alternative of a metal-semi-conductor-metal device structure, where photocurrent is directed by the difference in work function between the two metals, also cannot be used because the electric field created by available asymmetric contact materials is insufficient to separate the singlet exciton into electron and hole polarons. Therefore, alternative device architectures are needed. 

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