Enhanced Room‐Temperature Photoluminescence Quantum Yield in Morphology Controlled J‐Aggregates
Surendra B. Anantharaman, Joachim Kohlbrecher, Gabriele Rainò, Sergii Yakunin, Thilo Stöferle, Jay B. Patel, Maksym V. Kovalenko, Rainer F. Mahrt, Frank Nüesch, Jakob Heier
Abstract
). Applications of these high color purity emitters, however, are hampered by the rather low photoluminescence quantum yields reported for cyanine J-aggregates, even when formed in solution. Here, it is demonstrated that cyanine J-aggregates can reach an order of magnitude higher photoluminescence quantum yield (increase from 5% to 60%) in blend solutions of water and alkylamines at room temperature. By means of time-resolved photoluminescence studies, an increase in the exciton lifetime as a result of the suppression of non-radiative processes is shown. Small-angle neutron scattering studies suggest a necessary condition for the formation of such highly emissive J-aggregates: the presence of a sharp water/amine interface for J-aggregate assembly and the coexistence of nanoscale-sized water and amine domains to restrict the J-aggregate size and solubilize monomers, respectively.