Long Persistent Luminescence Enabled by Dissociation of Triplet Intermediate States in an Organic Guest/Host System.

Organic guest/host systems with long persistent luminescence benefiting from the formation of a long-lived charge-separated state have recently been demonstrated. However, the photogeneration mechanism of such key charge-separated states remains elusive. Here, we report the identification of intermediate triplet states with mixed local excitation and charge-transfer character that connect the initial photoexcited singlet states and the long-lived charge-separated states. Using time-resolved optical spectroscopy, we observe the intersystem crossing from photoexcited singlet charge-transfer states to triplet intermediate states on a time scale of ∼52 ns. Temperature-dependent measurements reveal that the long-lived triplet intermediate states ensure a relatively high efficiency of diffusion-driven charge separation to form the charge-separated state responsible for LPL emission. The findings in this work provide a rationale for the development of new LPL materials that may also improve our understanding of the mechanism of photon-to-charge conversion in many organic optoelectronic devices.

Optimization of Low-Dimensional Components of Quasi-2D Perovskite Films for Deep-Blue Light-Emitting Diodes.

Compared to efficient green and near-infrared light-emitting diodes (LEDs), less progress has been made on deep-blue perovskite LEDs. They suffer from inefficient domain [various number of PbX6 - layers (n)] control, resulting in a series of unfavorable issues such as unstable color, multipeak profile, and poor fluorescence yield. Here, a strategy involving a delicate spacer modulation for quasi-2D perovskite films via an introduction of aromatic polyamine molecules into the perovskite precursor is reported. With low-dimensional component engineering, the n1 domain, which shows nonradiative recombination and retarded exciton transfer, is significantly suppressed. Also, the n3 domain, which represents the population of emission species, is remarkably increased. The optimized quasi-2D perovskite film presents blue emission from the n3 domain (peak at 465 nm) with a photoluminescence quantum yield (PLQY) as high as 77%. It enables the corresponding perovskite LEDs to deliver stable deep-blue emission (CIE (0.145, 0.05)) with an external quantum efficiency (EQE) of 2.6%. The findings in this work provide further understanding on the structural and emission properties of quasi-2D perovskites, which pave a new route to design deep-blue-emissive perovskite materials.

Enabling long-lived organic room temperature phosphorescence in polymers by subunit interlocking.

Long-lived room temperature phosphorescence (LRTP) is an attractive optical phenomenon in organic electronics and photonics. Despite the rapid advance, it is still a formidable challenge to explore a universal approach to obtain LRTP in amorphous polymers. Based on the traditional polyethylene derivatives, we herein present a facile and concise chemical strategy to achieve ultralong phosphorescence in polymers by ionic bonding cross-linking. Impressively, a record LRTP lifetime of up to 2.1 s in amorphous polymers under ambient conditions is set up. Moreover, multicolor long-lived phosphorescent emission can be procured by tuning the excitation wavelength in single-component polymer materials. These results outline a fundamental principle for the construction of polymer materials with LRTP, endowing traditional polymers with fresh features for potential applications.

Correction: Direct Z scheme-fashioned photoanode systems consisting of Fe2O3 nanorod arrays and underlying thin Sb2Se3 layers toward enhanced photoelectrochemical water splitting performance.

Correction for 'Direct Z scheme-fashioned photoanode systems consisting of Fe2O3 nanorod arrays and underlying thin Sb2Se3 layers toward enhanced photoelectrochemical water splitting performance' by Yong Zhou et al., Nanoscale, 2019, DOI: 10.1039/c8nr08292h.

Direct Z scheme-fashioned photoanode systems consisting of Fe2O3 nanorod arrays and underlying thin Sb2Se3 layers toward enhanced photoelectrochemical water splitting performance.

An elegant Z-scheme-fashioned photoanode consisting of Fe2O3 nanorod arrays and underlying thin Sb2Se3 layers was rationally constructed. The photocurrent density of the Sb2Se3-Fe2O3 Z-scheme photoanode reached 3.07 mA cm-2 at 1.23 V vs. RHE, three times higher than that of pristine Fe2O3 at 1.03 mA cm-2. An obvious cathodic shift of the photocurrent onset potential of about 200 mV was also observed. The transient photovoltage response demonstrates that the suitable band edges (ECB ∼ -0.4 eV and EVB ∼ 0.8 eV) of Sb2Se3, match well with Fe2O3 (ECB ∼ 0.29 eV and EVB ∼ 2.65 eV), permitting the photoexcited electrons on the conduction band of the Fe2O3 to transfer to the valence band of Sb2Se3, and recombine with the holes therein, thus allowing a high concentration of holes to collect in the Fe2O3 for water oxidation. The transient absorption spectra further corroborate that the built-in electric field in the p-n heterojunction leads to a more effective separation and a longer lifetime of the charge carriers.

Integration of FexS electrocatalysts and simultaneously generated interfacial oxygen vacancies to synergistically boost photoelectrochemical water splitting of Fe2O3 photoanodes.

Integration of FexS electrocatalysts and simultaneously generated interfacial oxygen vacancies (VO) was designed to promote the water splitting performance of Fe2O3 photoanodes, in which a synergistic effect remarkably reduces the carrier recombination, increases the number of active sites, and facilitates the photogenerated holes to participate in water oxidation.