Robin Petit, Pieter Schiettecatte, Korneel Molkens, Matthias M. Minjauw, Eder Antonio Castillo-Ruiz, Hannes Van Avermaet, Luca Giordano, Andreas Werbrouck, Pieter Geiregat, Henk Vrielinck, Christophe Detavernier, Philippe F. Smet, Zeger Hens
Reliability is an essential aspect of emerging optoelectronic technologies based on colloidal quantum dots (QDs). Even so, the fundamental chemical processes that deteriorate the performance of QD-based devices remain poorly understood. Here, we identify a single process of failure that leads to photoluminescence (PL) quenching of InP-based QDs under continuous illumination in an O 2 -containing atmosphere. We first demonstrate that a rapid loss of PL efficiency occurs under combined O 2 /light exposure. While no noticeable changes in chemical composition of the QDs occur, we show by femtosecond transient absorption a direct correlation between the PL quenching and the buildup of a population of charged QDs, in which nonemissive trions are formed after photoexcitation. Using electron paramagnetic resonance, we relate QD charging to the transfer of a photoexcited electron to physisorbed O 2, thereby forming superoxide anions. Understanding this single process of failure is critical for enhancing the reliability of devices using InP-based QDs for photoluminescent color conversion and electroluminescent light emission.