Small organic molecules for next generation electronics

Abstract

In this PhD thesis attention has been focused on the theoretical design of organic small molecules for next generation electronics. The task of this thesis has concerned with the theoretical analysis of the operational performances of small dyes in photovoltaic solar cells, both in bulkheterojunction and dye sensitized solar cells; with particular emphasis on the theoretical analysis of the rates of the elementary electron transfer processes. A full quantum mechanics procedure for computing the rates of elementary electron transfer processes has been developed. The procedure starts from the Fermi Golden Rule (FGR) expression of the rate of electronic transitions and makes use of a rigorous evaluation of the Franck-Condon weighted density of states, performed by Kubo’s generating function approach. The analysis of electron transfer rates has revealed to be a very powerful tool for investigating structure-property relationships for the employment of small organic molecules in photovoltaic solar cells. The methodology has been applied to a class of small organic molecules, which show different power energy conversion efficiencies. The different efficiencies of the dyes have been attributed to very different rates of photoinduced electron transfer, the first step of energy conversion process in any type of photovoltaic solar cell. The last part of this thesis has been devoted to a very important task for next generation electronics: the rational design of new N-rich fused-ring heteroaromatics small organic molecules for n-type charge transport in thin layers. The substitution of CH units with nitrogen atoms is particularly appealing because, it offers the possibility of tuning the electron donor/acceptor character of the molecule. [edited by author]