We demonstrate reversible quenching of the photoluminescence from single CdSe/ZnS colloidal quantum dots embedded in thin films of the molecular organic semiconductor N,N'-diphenyl-N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine (TPD) in a layered device structure. Our analysis, based on current and charge carrier density, points toward field ionization as the dominant photoluminescence quenching mechanism. Blinking traces from individual quantum dots reveal that the photoluminescence amplitude decreases continuously as a function of increasing forward bias even at the single quantum dot level. In addition, we show that quantum dot photoluminescence is quenched by aluminum tris(8-hydroxyquinoline) (Alq3) in chloroform solutions as well as in thin solid films of Alq3 whereas TPD has little effect. This highlights the importance of chemical compatibility between semiconductor nanocrystals and surrounding organic semiconductors. Our study helps elucidate elementary interactions between quantum dots and organic semiconductors, knowledge needed for designing efficient quantum dot organic optoelectronic devices.

All-inorganic cesium lead halide perovskite nanocrystals have been widely investigated as promising materials for light and display. The primary challenge for their practical application is development of highly efficient and...

Light emission from single colloidal CdSe/ ZnS ͑core/shell͒ nanocrystals embedded in electrically driven organic light emitting devices is demonstrated at room temperature. Spectral diffusion and blinking from individual quantum dots were observed both in electro-and photoluminescence. The authors propose a model in which the nanocrystals act as seeds for the formation of current channels that lead to enhanced exciton recombination in the vicinity of the quantum dots. This work demonstrates that individual semiconductor nanocrystals can serve as emissive probes in organic light emitting devices and that they can be used to manipulate device structure and properties at the nanometer scale.

We present a technique for making nanoscale gaps with work function offsets based on electromigrating leads composed of two different metals. Electroluminescence spectra from plain metal gaps with and without CdSe/ZnS (core/shell) nanocrystals are qualitatively very similar and exhibit features that are much broader than the photoluminescence spectra obtained from the same nanocrystals. These observations can be explained by inelastic scattering of conduction electrons in the metal leads or by electroluminescence from small metallic clusters that can form during the fabrication process. However, electroluminescence that spectrally coincides with nanocrystal photoluminescence can be observed in devices containing nanocrystals formed by electromigrating Pt leads bridged with small indium islands. This suggests that electromigrating leads made of different metals is a promising route to fabricating nanoscale gaps with work function offsets for optoelectronic devices.

Remarkable progress in power conversion efficiency of perovskite solar cells (PSCs) has been achieved over the last decade, reaching 25.5%. However, transferring these accomplishments from individual small-size devices into large-area modules while preserving their commercial competitiveness compared to other thin-film solar cells remains a challenge. A major obstacle is to reduce the resistive losses and the number of intrinsic defects of electron transport layers (mesoporous TiO2, ETL) and to fabricate high-quality large-area perovskite films. Here, we report a facile solvothermal method to synthesize single-crystalline TiO2 rhombus-like nanoparticles with exposed {001} facets. Owing to their low lattice mismatch with the perovskite absorber, high electron mobility and lower density of defects, single-crystalline TiO2 nanoparticle-based small-size devices (0.09 cm2) achieve an efficiency of 24.05% and a fill factor of 84.7%. Importantly, these devices maintain about 90% of their initial performance after continuous operation for 1400 h. Combined with vacuum quenching-assisted techniques, we have fabricated large-area modules and obtained a certified efficiency of 22.72% with an active area of nearly 24 cm2. This represents the highest efficiency modules with the lowest efficiency loss between small-size devices and modules, enabling to reproducibly fabricate stable and efficient PSC modules.