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Highly efficient vacuum-deposited CsPbBr3 perovskite light-emitting diodes (PeLEDs) are demonstrated by introducing a separate polyethylene oxide (PEO) passivation layer. A CsPbBr3 film deposited on the PEO layer via thermal co-evaporation of CsBr and PbBr2 exhibits an almost 50-fold increase in photoluminescence quantum yield intensity compared to a reference sample without PEO. This enhancement is attributed to the passivation of interfacial defects of the perovskite, as evidenced by temperature-dependent photoluminescence measurements. However, direct application of PEO to an LED device is challenging because of the electrically insulating nature of PEO. This issue is solved by doping PEO layers with MgCl2. This strategy results in an enhanced luminance and external quantum efficiency (EQE) of up to 6887 cd m-2 and 7.6%, respectively. To the best of our knowledge, this is the highest EQE reported to date among vacuum-deposited PeLEDs.

We report the synthesis of Bi-based lead-free halide perovskite nanocrystals (NCs) via a ligand-assisted reprecipitation (LARP) method. Detailed chemical analysis of the synthesized Cs–Bi–Br NCs, w...

Highly efficient vacuum-deposited CsPbBr

We report the formation of a new class of solvent-intercalated two-dimensional (SI-2D) formamidinium lead halide perovskites. They can be mixed with three-dimensional (3D) stoichiometric perovskites by controlling the ratio of the precursor solutions. The composite leads to greatly improved photoluminescence quantum yield (PLQY) over the 3D compound. The enhanced PLQY is attributed to a type-I band alignment between the 3D and SI-2D, as revealed by first-principles calculations, which results in confined excitons with enhanced radiative recombination. The films exhibited excellent thermal and air stability retaining PLQY > 20% over 2 months in ambient conditions. Assemblies of halide perovskites with mixed dimensionality offer a pathway to enhance optoelectronic performance and device lifetimes.

Korea Space Launch Vehicle-I (KSLV-I) carrying the STSAT-2A satellite, made its maiden flight on August 25, 2009. Liftoff was from the Korea Aerospace Research Institute (KARI) launch site at the Naro Space Center in a southern coastal province of the Korean peninsula. A video telemetry system provided visual monitoring of flight critical events, as well as dynamic moving images, through two cameras equipped on the upper stage. This paper describes the development of the onboard video system consisting of two video cameras, a video compression unit and an RF transmitter meeting the requirements of the KSLV-I launch vehicle. During the flight, the ETTARS, an especially reconstructed small telemetry ground station for the KSLV-I, received the video telemetry data and simultaneously measured automatic gain control (AGC) signal levels from the receiver. The onboard video system achieved a 15fps video rate, flew with a 2Mbps data rate and transmitted data using NRZ-L PCM/FM in the S-band. Errors on real telemetry channels occurred as predicted by link budget equations based on thermal noise and multipath interference. According to error analysis, the BER versus SNR performance degradation from the laboratory reference was about 1dB, which is close to expected limit.

In general, rocket or satellite circuit designers focus on reducing temperature of electronic devices in order to enhance electronic unit`s reliability. This paper describes the quantitative analysis result of activation energy as well as device temperature effects to the system reliabilities. The quantitative analysis result shows that activation energy of device has more effects on system reliability than temperature does. And this paper suggests a strategy for enhancement of reliability during devices placement on PCB with simulation results.

Pyro-shock measurement system in launch vehicle is necessary to validate structural robustness and to prepare environmental qualification criteria for launch vehicle systems. This paper describes design, development and function test of prototype pyro-shock recorder to be employed on KSLV-I in the near future. Due to the limitation of telemetry transmission rate, pyro-shock recorder acquires and stores the shock sensor data with high sampling rate in short period and sends the data to the KSLV-I telemetry system with lower data rate. Signal conditioning in pyro-shock recorder is designed to enhance signal-to-noise ratio through proper placement of anti-aliasing filter.

The third-generation Korean sounding rocket, KSR-III, was successfully launched on Nov. 28, 2002 from the western coastal area of the Korean Peninsula. The previous KSR-I and -II series had employed a solid propulsion system whereas the KSR-III utilizes Korea’s first liquid propulsion system. The prime objective of the mission was to evaluate the performance of the liquid propulsion system. The onboard electronics system of the KSR-III is an enhanced version of the ones used in the previous series. The system has extended data channels and has adopted a distributed data processing system using the RS-485 bus network. The rocket has various sensors to measure physical characteristics such as temperature, pressure, strain, acceleration, etc., and has scientific instruments including an ozone detector and two magnetometers. The flight data is transmitted to the ground station in real time by the onboard telemetry system. The onboard electronics system of the KSR-III mainly consists of telemetry, an RF subsystem, a tele-command system, a power supply system, and scientific payloads. Herein, we present an overview of the enhanced electronics system of the KSR-III and representative flight test results analyses including scientific data are discussed.

KSLV (Korea Space Launch Vehicle)-I is under development to place a 100-kg class satellite into a low earth orbit of 300times1500km. KSLV-I telemetry system will be composed of two telemetry streams: a lower (first) stage telemetry stream and an upper (second) stage telemetry stream. Different from the previously developed telemetry system by KARI for KSR (Korea Sounding Rocket) series, the new telemetry system has been required to meet the enhanced requirements on telemetry system. This paper introduces a new development of telemetry system for KSLV-I upper stage telemetry with MIL-STD-1553B data bus emphasizing on the design, implementation, evaluation test and salient features of the telemetry system

This paper includes development of a distributed data processing system for both space mission vehicles and test results by ground experiment. We developed test models of OBC (On-Board Computer), RIU (Remote Interface Unit), and MIL-STD-1553B data bus to meet requirements of a space vehicle. OBC and RIU hardware specifications, memory size, number of channels, data acquisition frequency and CPU throughput are designed followed by quantitative analysis considering its mission requirements. Tests of the developed systems were conducted with a satellite attitude control simulator to demonstrate their applicability on space mission vehicles. Experimental results show the developed system can be applied to space mission vehicles through further enhancement of performance in the future.