Ultra-Lightweight, Flexible InGaP/GaAs Tandem Solar Cells with a Dual-Function Encapsulation Layer.

Lightweight, flexible solar cells from III-V semiconductors offer new application opportunities for devices that require a power supply, such as cars, drones, satellites, or wearable devices, due to their outstanding efficiency and power-to-weight ratio (specific power). However, the specific power and stability of flexible photovoltaic (PV) devices need to be enhanced for use in such applications because current flexible PV devices are vulnerable to moisture and heat. Here, we develop ultra-lightweight, flexible InGaP/GaAs tandem solar cells with a dual-function encapsulation layer that serves as both a moisture barrier and an antireflection coating for the active device layer. Using a thin polymer film as a substrate and an ultrathin metal as a bonding layer, the total weight of the device is dramatically reduced. Therefore, the specific power of our solar cells is remarkably high with a value of over 5000 W/kg under the AM 1.5G solar spectrum. Additionally, there is no degradation even if the solar cells are exposed to harsh environmental conditions.

Temperature dependence of the Auger recombination coefficient in InGaN/GaN multiple-quantum-well light-emitting diodes.

This study investigated the temperature dependence of the Auger recombination coefficient (C) in an InGaN/GaN blue multiple-quantum-well (MQW) light-emitting diode structure at temperatures between 20 and 100°C. The temperature dependence of C was determined by fitting the measured external quantum efficiency (EQE) data using an analytical model or numerical simulation. In the analytical model, the carrier density in InGaN MQWs was assumed to be constant and independent of temperature. In contrast, the inhomogeneous carrier distribution in MQWs and its temperature-dependent redistribution were included in the numerical simulation. When the analytical model was employed to fit the EQE curve, C decreased with increasing temperature. On the other hand, when the numerical simulation was employed, C increased steadily by ∼31% as the temperature was increased from 20 to 100°C. We found that the temperature-dependent carrier distribution is important to consider when determining the temperature dependence of the Auger recombination coefficient in InGaN MQW structures.

Deterministic Integration of Quantum Dots into on-Chip Multimode Interference Beamsplitters Using in Situ Electron Beam Lithography.

The development of multinode quantum optical circuits has attracted great attention in recent years. In particular, interfacing quantum-light sources, gates, and detectors on a single chip is highly desirable for the realization of large networks. In this context, fabrication techniques that enable the deterministic integration of preselected quantum-light emitters into nanophotonic elements play a key role when moving forward to circuits containing multiple emitters. Here, we present the deterministic integration of an InAs quantum dot into a 50/50 multimode interference beamsplitter via in situ electron beam lithography. We demonstrate the combined emitter-gate interface functionality by measuring triggered single-photon emission on-chip with g(2)(0) = 0.13 ± 0.02. Due to its high patterning resolution as well as spectral and spatial control, in situ electron beam lithography allows for integration of preselected quantum emitters into complex photonic systems. Being a scalable single-step approach, it paves the way toward multinode, fully integrated quantum photonic chips.