Photovoltaic device hole transporting material

Working in collaboration with Reynolds, we have fabricated organic photovoltaic devices in which the active materials were assembled by using the LbL method [53]. In this work, the donor and hole transporting materials were the anionic CPEs PPE-SOs and PPE-EDOT-SO , whereas the acceptor and electron transport material was a cationic fullerene derivative, Cso-NHa (Scheme 14.13). The active layers were constructed atop an ITO substrate that was precoated with a PEDOT-PSS film (spin-coated). The PPE(—)/C6o—NHa bilayers were deposited through the LbL method, and the effect of active layer thickness on device performance was explored. Figure 14.20 shows a schematic... 

Photovoltaic devices based on pure 29 and 29 PCBM blend as the active layer is fabricated. It was interesting to observe that a device with pure 29 showed a higher power conversion efficiency (0.05%) compared to that consisting of a 29/PCBM blend (0.0.0024% to 0.041%). The good performance in the photovoltaic cells with 29 only was attributed to the efficient charge separation process and that the material exhibits efficient hole and electron transport. The C6o moieties facilitated that electron transport, while the holes are transported via the hopping between Pt2-thiophene units. 

In addition to the reqnirements on the energy levels of donor and acceptor for interfacial charge separation, it is necessary that the work function of the electroncollecting electrode shonld be well matched to the LUMO of the acceptor material, and that of the hole-collecting material be well matched to the HOMO of the donor. In bnlk heterojunctions, photovoltaic action can only be achieved if electronic contact is made to the photoactive material nsing snitable asymmetric electrodes. For high efficiency the electrodes shonld also be condnctive and well matched in energy to the electron or hole transport levels. The constraints on electrode materials will be treated in more detail in Sections 7.5 and 7.6.5. The development and optimisation of bilayer and BHJ device types are reviewed in Sections 7.3 and 7.4 respectively. 

Nanostructured semiconducting block copolymers containing triphenylamine as hole transport moiety and perylene bisimide as dye and electron transport, have been investigated in view of applications in photovoltaic devices. The polymers show nanowire like structure which formation is driven by the crystallization of perylene bisimides via n- n stacking and since this self-assembly gives rise to domains size comparable to the exciton diffusion length, these materials offer perspectives for the implementation of organic solar cells [357]. 

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