Narrow electroluminescence linewidths for reduced nonradiative recombination in organic solar cells and near-infrared light-emitting diodes

Minimization of non-radiative recombination losses is essential to transcend the efficiency of state-of-the-art organic solar cells (OSCs) and near-infrared (NIR) organic light-emitting diodes (OLEDs). Indeed, reduced non-radiative processes will result in a high electroluminescence (EL) external quantum efficiency (EQEEL) and low non-radiative voltage losses (ΔVOC,nr) for OSCs. Here, we study the EL properties of a set of polymer-small molecule blends and find a relationship between the EL emission linewidth, EQEEL and ΔVOC,nr. Based on these findings, we reduce ΔVOC,nr from the typical values around 250 mV down to an unprecedented value of 155 mV using a blend comprising a low-molecular-weight PM6 polymer donor and a highly emissive non-fullerene acceptor (Y16F). Importantly, the PM6:Y16F blend yields an EQEEL (0.52%) among the best reported fluorescent NIR-OLEDs in the 900nm range.. These findings clearly indicate the existence of organic material blends which combine both excellent photovoltaic and electroluminescent properties.