Core-shell carbon-polymer quantum dot passivation for near infrared perovskite light emitting diodes

High-performance perovskite light-emitting diodes (PeLEDs) require a high quality perovskite emitter and appropriate charge transport layers to facilitate charge injection and transport within the device. Solution-processed n-type metal oxides represent a judicious choice for the electron transport layer (ETL); however, they don't always present suitable surface properties and energetics in order to be compatible with the perovskite emitter. Moreover, the emitter itself exhibits poor nanomorphology and defect traps that compromise the device performance. Here we modulate the surface properties and interface energetics of the tin oxide (SnO2) ETL with the perovskite emitter by using an amino functionalized difluoro{2-[1-(3,5-dimethyl-2H-pyrrol-2-ylidene-N)ethyl]-3,5-dimethyl-1H-pyrrolato-N}boron (BDP) compound and passivate the defects present in the perovskite with carbon-polymer core-shell quantum dots (PCDs) inserted into the perovskite precursor. Both these approaches synergistically improve the perovskite layer nanomorphology and enhance the radiative recombination. These properties resulted in the fabrication of near infrared (NIR) PeLEDs based on formamidinium lead iodide (FAPbI3) with a high radiance of 92 W sr-1 m-2, an external quantum efficiency (EQE) of 14% and reduced efficiency roll-off

Conformational analysis of octa- and tetrahalogenated tetraphenylporphyrins and their metal derivatives

A new maximally diagonal force field for molecular modelling of metalloporphyrins is developed and optimized on the crystal structures of nickel(II) porphine, nickel(II) mono-tert-butylporphyrin and nickel(II) di-tert-butylporphyrin. It is then used to investigate non-planar distortions of octa- and tetrachloro tetraphenylporphyrins (TPP) and their Ni(II) and Tb(III) complexes. Molecular mechanics (MM) calculations reproduced very well the structure of Tb(III) octachloro-TPP (so far the only example of a crystallographically characterized chloro TPP metal derivative). Normal-coordinate structural decomposition (NSD) analysis was performed on the equilibrium structures obtained by MM calculations. As expected, sad distortion dominates in octachloro structures irrespective of the presence or the size of the central metal atom; dom distortion dominates in tetrachloro structures with large Th(III) central atom, while sad, ruf, wav and pro distortions are present in various amounts in other tetrachloro structures (TPP free base and Ni(II) complex) depending on the pattern of peripheral chloro substitution on the pyrrole rings. Other observed regularities are: reduction of the conformational flexibility of the porphyrin core upon metallation, and increase of the dihedral angle between the phenyl groups and the mean LSQ plane of the porphyrin core, as well as the overall increase in structural regularity upon the increase of the size of the central metal atom. (C) 2001 Elsevier Science B.V. All rights reserved

N@C60-porphyrin: a dyad of two radical centers.

Dyads of endohedral nitrogen fullerene and porphyrin have been synthesized. In the two-radical-center dyad, the copper(II) tetraphenylporphyrin suppressed the electron spin resonance (ESR) signal of N@C(60) through intramolecular dipolar coupling with a strength of 27.0 MHz. Demetalation of the metalloporphyrin moiety of the dyad, which effectively turned the two-radical-center dyad into a single-radical-center dyad, recovered 82% of the ESR signal of N@C(60). Such mechanism of switching a spin state on and off could find use in molecular spintronics applications