Improving Organic Photovoltaic Efficiency via Heterophase Homojunction Copper Indium Sulfide Nanocrystals

Abstract

Eco‐friendly heterophase homojunction copper indium sulfide quantum dots (HH‐CIS QDs) terminated by short hydroxyl ligands are integrated into nonfullerene organic solar cells (OSCs) for the first time. Experimental results exhibit that this novel nanostructure can improve sunlight absorption and charge transfer ability, harvesting more photons and converting them to charge carriers. Additionally, the formation of hydrogen bonds between 2‐mercaptoethanol‐capped HH‐CIS QDs and the interface modification layer is beneficial for better interfacial contact, which promotes work function modification, reduces surface roughness, and increases interfacial charge transfer. Benefiting from HH‐CIS QDs incorporation, nonfullerene OSCs involving two different types of photoactive layers and three different types of electron transport layers all demonstrate improved photoelectric conversion efficiency (PCE). With QDs concentration optimization, nonfullerene OSCs with the PM6:ITIC‐4F and PM6:Y6 absorbers exhibit excellent PCEs of 14.04% and 16.26%, respectively. As compared to those reported previously, HH‐CIS QDs into the interface between the electron charge layer and photoactive layer lead to significant performance improvement, with both achieve PCEs and enhancement factors among the highest ones reported for various QD‐integrated OSCs. The results strongly suggest that the rational design of QDs and their optimal integration are critical for performance enhancement.