as well as physical constraints. The successful operation of a hybrid solar cell requires a
type II heterojunction, which has cascading energy levels. This is required to allow
electrons to transport to the cathode and holes to transport to the anode. In order to
optimise the efficiency of hybrid solar cells, it is crucial to realise a trade-off in
performance of an inorganic acceptor based on increasing both Open Circuit Voltage
(Voc ) andShort Circuit Current (I
sc
).Recently, Xiang et al. have used a hybrid density
functional theory to analyse the electronic structure of inorganic acceptors and also to
predict the ideal qualities of a material to be coupled with P3HT, the most commonly
used polymeric donor (Xiang et al., 2009). They predict that the ideal inorganic
nanomaterial would have a band gap of 1.5 eV and a HOMO level offset of 0.3 eV. This
information is displayed in Fig. 1.