Enhancement of photoluminescence efficiency in binary quantum dot arrays in hybrid organic/inorganic materials

Abstract

The photoluminescence (PL) quantum efficiency of dense semiconductor colloidal quantum dot (QD) arrays is significantly reduced by the quenching of the optical excitons via defect-induced nonradiative decay channels. This luminescence quenching is facilitated by the rapid migration of excitons between neighboring QDs via resonant Förster transfer processes. We propose to mitigate this quenching by using nonradiative “spacer” quantum dots (SQDs) to separate radiative primary quantum dots (PQDs). We have identified the maximum and minimum values of the PL quantum efficiency (PLQE) for different compositions of spacer-primary QD arrays. Using the kinetic Monte Carlo technique, we have found that for a given composition, the PLQE is highest for randomly distributed spacer and primary QDs, decreasing dramatically when clusters of SQDs and PQDs are formed. We have modeled cluster formation of QDs in binary QD arrays and determined the resultant PL properties. By comparing our simulation results with those we obtained experimentally, we have estimated the magnitude of the attractive pairwise van der Waals interaction between the QDs which is the driving force for QD cluster formation. We have also explored possible strategies to achieve the highest PLQE of the PQDs in hybrid organic/inorganic materials for photoelectronics and we found that lowering the mixing time of the binary QD mixture can improve the PLQE.