ABSTRACT
In quantum dot light-emitting diodes (QLEDs), even seemingly with interfacial exciton quenching between quantum dots (QDs) and the electron transport layer (ETL) limiting the device efficiency, the internal quantum efficiency of such QLEDs approaches 100%. Therefore, it is a puzzle that QLEDs exhibit high performance although they suffer from interfacial exciton quenching. In this work, we solve this puzzle by identifying the cause of the interfacial exciton quenching. By analyzing the optical characteristics of pristine and encapsulated QD-ETL films, the interfacial exciton quenching in the pristine QD-ETL film is attributed to O2-induced charge transfer. We further investigate the charge transfer mechanism and its effect on the performance of QLEDs. Finally, we show the photodegradation of the pristine QD-ETL film under UV irradiation. Our work bridges interfacial exciton quenching and high performance in hybrid QLEDs and highlights the significance of encapsulation in QLEDs.
ABSTRACT
Traditionally, ZnS or ZnSe is chosen as the shell material for InP quantum dots (QDs). However, for green or blue InP QDs, the ZnSe shell will form a type-II structure resulting in a redshift of the emission spectrum. Although the band gap of ZnS is wider, its lattice mismatch with InP is larger (â¼7.7%), resulting in more defect states and lowered quantum yield (QY). To overcome the above problems, we introduced the intermediate ZnMnS layer in InP/ZnMnS/ZnS QDs. The wide band gap of the intermediate layer (3.7 eV) can confine the electrons and holes in the core completely, and the formation of the type-II structure is avoided. As a result, green InP-based QDs with QY up to 80% were obtained. By adjusting the halogen ratios of the ZnX2 precursor, the minimum and maximum emission peaks are 470 and 620 nm, respectively, covering the whole visible range. Finally, after optimizing the coating shell process, the maximum external quantum efficiency of QD light-emitting diodes fabricated from this InP-based green light QDs can reach 2.7%.
ABSTRACT
In rat's sensory neurons, hyperpolarization-activated inward currents (Ih) play an essential role in mediating action potentials and contributing to neuronal excitability. Classified by the size of neurons and ages, we studied the Ih and transcription levels of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels using electrophysiology and the single-cell RT-PCR. In voltage-clamp studies, Ih and half-maximal activation voltage (V1/2) changed with age and size. An analysis of all HCN subtypes in dorsal root ganglion (DRG) neurons by single-cell RT-PCR was carried out. HCN1 and HCN3 in medium-small elderly neurons had a weak expression. HCN2 in newborns and HCN4 in elderly rats also had a weak expression. The aim of this study is to examine the age-related Ih and HCN channels subunits in different ages and sizes of DRG neurons. The results would be significant in understanding the physiological and pathophysiological function of different sizes of DRG neurons in different age periods.
