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Interfacial chemistry and energetics significantly impact the performance of photovoltaic devices. In the case of Pb-containing organic metal halide perovskites, photoelectron spectroscopy has been...

Tailor-made additives, which are molecules that share the same molecular structure as a parent molecule with only slight structural variations, have previously been demonstrated as a useful means to control crystallization dynamics in solution. For example, tailor-made additives can be added to solutions of a crystallizing parent molecule to alter the crystal growth rate, size, and shape. We apply this strategy as a means to predictably control morphology in molecular bulk-heterojunction (BHJ) photovoltaic cells. Through the use of an asymmetric oligomer substituted with a bulky triisobutylsilyl end group, the morphology of BHJ blends can be controlled resulting in a near doubling (from 1.3 to 2.2%) in power conversion efficiency. The use of tailor-made additives provides promising opportunities for controlling crystallization dynamics, and thereby film morphologies, for many organic electronic devices such as photovoltaics and field-effect transistors.

The new metalloporphyrin Pt(tptnp), where tptnp = tetraphenyltetranaphtho[2,3]porphyrin, has been prepared and subjected to photophysical and electrooptical device studies. In degassed toluene solution at room temperature Pt(tptnp) features efficient phosphorescence emission with lambda(max) 883 nm with a quantum efficiency of 0.22. The complex has been used as the active phosphor in polymer and organic light-emitting diodes. Polymer light-emitting diodes based on a spin-coated emissive layer consisting of a blend of Pt(tptnp) doped in poly(9-vinylcarbazole) and 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole exhibit near-IR emission with lambda(max) 896 nm, with a maximum external quantum efficiency (EQE) of 0.4% and a maximum radiant emittance of 100 muW/cm(2). Organic light-emitting diodes prepared via vapor deposition of all layers and that feature an optimized multilayer hole injection and electron blocking layer heterostructure with an emissive layer consisting of 4,4'-bis(carbazol-9-yl)biphenyl (CBP) doped with Pt(tptnp) exhibit a maximum EQE of 3.8% and a maximum radiant emittance of 1.8 mW/cm(2). The polymer and organic light-emitting diodes characterized in this study exhibit record high efficiency for devices that emit in the near-IR at lambda800 nm.