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.

Automated summary

This study focused on polymer-small molecule blends and successfully reduced the nonradiative voltage losses of organic solar cells from typical values around 250 mV to an unprecedented value of 155 mV, while achieving high external quantum efficiency. The findings demonstrate the potential of organic material blends that combine excellent photovoltaic and electroluminescent properties.