Suppressed Triplet Exciton Diffusion Due to Small Orbital Overlap as a Key Design Factor for Ultralong-Lived Room-Temperature Phosphorescence in Molecular Crystals.

Persistent room-temperature phosphorescence (RTP) under ambient conditions is attracting attention due to its strong potential for applications in bioimaging, sensing, or optical recording. Molecular packing leading to a rigid crystalline structure that minimizes nonradiative pathways from triplet state is often investigated for efficient RTP. However, for complex conjugated systems a key strategy to suppress the nonradiative deactivation is not found yet.

Nanoscale triplet exciton diffusion via imaging of up-conversion emission from single hybrid nanoparticles in molecular crystals.

Up-conversion materials composed of donor and acceptor molecules which convert low energy photons into higher energy ones by triplet-triplet annihilation can improve the sensitivity of photocatalysts or the efficiency of solar cells. The use of crystalline materials can lead to a decrease in the up-conversion threshold intensity due to increased diffusion length L of triplet excitons. Here, we demonstrate direct microscopic imaging of triplet exciton diffusion in polycrystalline films.

1-, 3-, 6-, and 8-Tetrasubstituted Asymmetric Pyrene Derivatives with Electron Donors and Acceptors: High Photostability and Regioisomer-Specific Photophysical Properties.

The systematic synthesis of five 1-, 3-, 6-, and 8-tetrasubstituted asymmetric pyrenes with electron donor and acceptor moieties is presented, together with an examination of their photophysical properties. Pyrene derivative PA1, containing one formyl and three piperidyl groups, showed bright solvatochromic fluorescence from green (λem = 557 nm, ΦFL = 0.94 in hexane) to red (λem = 648 nm, ΦFL = 0.