Towards efficient near-infrared fluorescent organic light-emitting diodes

The design of near-infrared (NIR) organic emitters is hindered by the energy gap law (*E_G*-law) and aggregation quenching. This research achieves unprecedented results by addressing these limitations synergistically. Porphyrin oligomers with increasing length attenuate *E_G*-law effects by suppressing non-radiative rate growth and increasing radiative rate via oscillator strength enhancement. Side chains suppress aggregation quenching. The logarithmic rate variation in the non-radiative rate vs. *E_G* is suppressed by an order of magnitude. Organic light-emitting diodes demonstrate an average external quantum efficiency of ~1.1% at 850 nm, a promising result for a heavy-metal-free emitter. A novel quantitative model of internal quantum efficiency for active layers supporting triplet-to-singlet conversion is also presented. These findings provide a strategy for designing high-luminance NIR emitters.

Alessandro Minotto, Ibrahim Bulut, Alexandros G. Rapidis, Giuseppe Carnicella, Maddalena Patrini, Eugenio Lunedei, Harry L. Anderson, Franco Cacialli