Hole transparent and hole blocking transport in single-crystal-like organic heterojunction: when rods hold up disks

Transport of charge carriers and optoelectronic applications of highly ordered metal phthalocyanine heterojunction thin films

Organic semiconductor thin films based on polycrystalline small molecules exhibit many attractive properties that have already led to their applications in optoelectronic devices, which can be produced by less expensive and stringent processes. Conduction of electric charges typically occurs in polycrystalline organic thin films. Unavoidably, the crystalline domain size, orientation, domain boundaries and energy level of the interface affect the transport of the charge carriers in organic thin films. In this comprehensive perspective, we focus on highly ordered organic heterojunction thin films fabricated by the weak epitaxy growth method. Transport of charge carriers in these highly ordered organic heterojunction thin films was systematically studied with various characterization techniques. Recent advances are presented in high-performance optoelectronic applications based on highly ordered organic heterojunction thin films, including organic photodetectors, photovoltaic cells, photomemory devices and artificial optoelectronic synapses.

Controlling Morphology and Molecular Packing of Alkane Substituted Phthalocyanine Blend Bulk Heterojunction Solar Cells

Systematic changes in the exocyclic substiution of core phthalocyanine platform tune the absorption properties to yield commercially viable dyes that function as the primary light absorbers in organic bulk heterojunction solar cells. Blends of these complementary phthalocyanines absorb a broader portion of the solar spectrum compared to a single dye, thereby increasing solar cell performance. We correlate grazing incidence small angle x-ray scattering structural data with solar cell performance to elucidate the role of nanomorphology of active layers composed of blends of phthalocyanines and a fullerene derivative. A highly reproducible device architecture is used to assure accuracy and is relevant to films for solar windows in urban settings. We demonstrate that the number and structure of the exocyclic motifs dictate phase formation, hierarchical organization, and nanostructure, thus can be employed to tailor active layer morphology to enhance exciton dissociation and charge collection efficiencies in the photovoltaic devices. These studies reveal that disordered films make better solar cells, short alkanes increase the optical density of the active layer, and branched alkanes inhibit unproductive homogeneous molecular alignment.