Design and fabrication of CuInS2/ZnS-based QLED for automotive lighting systems

This work reports the design, manufacturing and numerical simulation approach of a 6-pixel (4.5 mm2/pixel) electroluminescent quantum dot light emitting device (QLED) based on CuInS2/ZnS quantum dots as an active layer. The QLED device was fabricated using a conventional multi-layer thin film deposition. In addition, the electrical I-V curves were measured for each pixel independently, observing how the fabrication process and layer thickness have an influence in the shape of the plot. This experimental device, enabled us to create a computational model for the QLED based on the Transfer Hamiltonian approach to calculate the current density J (mA cm-2), the band diagram of the system, and the accumulated charge distribution. Besides, it is worth highlighting that the simulator allows the possibility to study the influence of different parameters of the QLED structure like the junction capacitance between the distinct multilayer set. Specifically, we found that the Anode-HIL interface capacitance has a greater influence in the I-V curve. This junction capacitance plays an important role in the current density increase and the QLED turn-on value when a forward voltage is applied to the device. The simulation enabled that influence could be controlled by the selection of the optimal thickness and transport layers during the experimental fabrication process. This work is remarkable since it achieves to fit simulation and experiment results in an accurate way for electroluminescent QLED devices; particularly the simulation of the device current, which is critical when designing the automotive electronics to control these new nanotechnology lighting devices in the future.

Band-like electron transport in 2D quantum dot periodic lattices: the effect of realistic size distributions

Electron mobility in nanocrystal films has been a controversial topic in the last few years. Theoretical and experimental studies evidencing carrier transport by hopping or showing band-like features have been reported in the past. A relevant factor to analyze transport results is the progressive improvement in quantum dot superlattice fabrication, leading to better regimented structures for which band-like transport would be more relevant. This work presents an efficient model to compute temperature-dependent band-like electronic mobilities in 2D quantum dot arrays when a realistic quantum dot size distribution is considered. Comparisons with experimental results are used to estimate these size distributions, in good agreement with data of the samples.