Si nanopillar arrays with nanocrystals produced by template-induced growth at room temperature

Well-aligned and closely-packed silicon nanopillar （SNP） arrays are fabricated by using a simple method with magnetron sputtering of Si on a porous anodic alumina （PAA） template at room temperature. The SNPs are formed by selective growth on the top of the PAA pore walls. The growth mechanism analysis indicates that the structure of the SNPs can be modulated by the pore spacing of the PAA and the sputtering process and is independent of the wall width of the PAA. Moreover, nanocrystals are identified by using transmission electron microscopy in the as-deposited SNP samples, which are related to the heat isolation structure of the SNPs. The Raman focus depth profile reveals a high crystallization ratio on the surface.

The enhancement of light-emitting efficiency using GaN-based multiple quantum well light-emitting diodes with nanopillar arrays

The quest for higher modulation speed and lower energy consumption has inevitably promoted the rapid development of semiconductor-based solid lighting devices in recent years. GaN-based light-emitting diodes （LEDs） have emerged as promising candidates for achieving high efficiency and high intensity, and have received increasing attention among many researchers in this field. In this paper, we use a self-assembled array-patterned mask to fabricate InGaN/GaN multi- quantum well （MQW） LEDs with the intention of enhancing the light-emitting efficiency. By utilizing inductively coupled plasma etching with a self-assembled Ni cluster as the mask, nanopillar arrays are formed on the surface of the InGaN/GaN MQWs. We then observe the structure of the nanopillars and find that the V-defects on the surface of the conventional structure and the negative effects of threading dislocation are effectively reduced. Simultaneously, we make a comparison of the photoluminescence （PL） spectrum between the conventional structure and the nanopillar arrays, achieved under an experimental set-up with an excitation wavelength of 325 mm. The analysis demonstrates that MQW-LEDs with nanopillar arrays achieve a PL intensity 2.7 times that of conventional LEDs. In response to the PL spectrum, some reasons are proposed for the enhancement in the light-emitting efficiency as follows： 1） the improvement in crystal quality, namely the reduction in V-defects; 2） the roughened surface effect on the expansion of the critical angle and the attenuated total reflection; and 3） the enhancement of the light-extraction efficiency due to forward scattering by surface plasmon polariton modes in Ni particles deposited above the p-type GaN layer at the top of the nanopillars.

Interface engineering of high performance all-inorganic perovskite solar cells via low-temperature processed TiO2 nanopillar arrays

All-inorganic perovskite solar cells suffer from low performance due to unsatisfactory carrier transport and light harvesting efficiency.Semiconductor nanopillar arrays can reduce light reflection loss and suppress exciton recombination dynamics in optoelectronic devices.In all-inorganic perovskite solar cells,few studies employing TiO_(2)nanopillar arrays(TiO_(2)NaPAs)have been reported to improve the device performance.Herein,well-arranged TiO_(2)NaPAs are chosen to enhance the interfacial contact between perovskite and electron transporting layers for improving the carrier transport.Notably,TiO_(2)NaPAs can be directly fabricated on rigid/flexible substrates at roughly room temperature by unique glancing angle deposition,which is more available than high-temperature hydrothermal/solvothermal methods.By embedding TiO_(2)NaPAs into chemical processable CsPbI2Br layers,continuous and intimate films are readily formed,guaranteeing large physical contact for facilitating more effective electron injection and charge separation.The vertically grown TiO_(2)NaPAs also provide a straightforward electron transporting path to electrodes.In addition,TiO_(2)NaPAs can guide the incident light and enhance the light-harvesting ability of CsPbI2Br films.As a result,the solar cell with TiO_(2)NaPAs displays a power conversion efficiency of 11.35%higher than planar control of 10.04%,and exhibits better long-term thermal stability.This strategy provides an opportunity by constructing direct interfacial regulation towards the performance improvement of inorganic perovskite solar cells.