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

The minimization of nonradiative 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 nonradiative processes will result in high electroluminescence (EL), external quantum efficiency (EQE(EL)), and low nonradiative voltage losses (Delta V-OC,V- 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 Delta V-OC,V-nr. Based on these findings, we reduce Delta V-OC,V-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 nonfullerene acceptor (Y16F). Importantly, the PM6:Y16F blend yields an EQE(EL) ( 0.52%) among the best reported fluorescent NIR-OLEDs in the 900-nm range. These findings clearly indicate the existence of organic material blends that combine both excellent photovoltaic and electroluminescent properties. European Union's Horizon 2020 research and innovation program under the Marie-Curie grant [88279]; FWOFWO [G0D0118N, G0B2718N, G0D1521N, I006320N, GOH3816-NAUHL]; European Research Council (ERC)European Commission [864625]; FWO Odysseus program [G0D0115N]