Temperature-dependent photoluminescence of surface-engineered silicon nanocrystals

In this work we report on temperature-dependent photoluminescence measurements (15–300 K), which have allowed probing radiative transitions and understanding of the appearance of various transitions. We further demonstrate that transitions associated with oxide in SiNCs show characteristic vibronic peaks that vary with surface characteristics. In particular we study differences and similarities between silicon nanocrystals (SiNCs) derived from porous silicon and SiNCs that were surface-treated using a radio-frequency (RF) microplasma system

Type-I alignment in MAPbI3 based solar devices with doped-silicon nanocrystals

In this work we couple silicon nanocrystals (Si NCs) with strong quantum confinement (< 4 nm diameter) with large grained MAPbI3 films combining the perovskites excellent transport properties with the unique opto-electronic properties of quantum confined Si NCs. The electronic structures of MAPbI3 and Si NCs, ideally aligned to form a type-I heterojunction, demonstrated improved carrier collection through a higher short-circuit current density (~ 20 mA cm−2) measured in photovoltaic test devices. The addition of p- and n-doped Si NCs within the MAPbI3 films also showed unexpected and interesting device performance improvements, where the typical perovskite degradation process in ambient conditions was considerably slowed down and the overall device efficiency was observed to increase under light soaking. We attribute these improvements to the presence of Si NCs, which helped maintain the perovskite film qualities for more than 14 days in open atmosphere

Silicon-based quantum dots: synthesis, surface and composition tuning with atmospheric pressure plasmas

The synthesis of silicon and silicon-based quantum dots (diameter < 5 nm) is discussed. Specifically the synthesis of Si-based quantum dots (QDs) by atmospheric pressure plasmas is reviewed and the most recent developments are also reported. Atmospheric pressure plasmas are then compared with other synthesis methods that include low pressure plasmas, wet chemistry, electrochemical etching and laser-based methods. Finally, progress in the synthesis of alloyed silicon QDs is discussed where the nanoscale Si-Sn and Si-C systems are reported. The report also includes a theoretical analysis that highlights some fundamental differences offered by plasmas at atmospheric pressure and that may provide opportunities for novel materials with advantageous properties

Synthesis of Copper-Based Nanostructures in Liquid Environments by Means of a Non-equilibrium Atmospheric Pressure Nanopulsed Plasma Jet

The influence of the liquid composition on the chemical and morphological properties of copper-based nanostructures synthesized by a non-equilibrium atmospheric plasma treatment is investigated and discussed. The synthesis approach is simple and environmentally friendly, employs a non-equilibrium nanopulsed atmospheric pressure plasma jet as a contactless cathode and a Cu foil as immersed anode. The process was studied using four distinct electrolyte solutions composed of distilled water and either NaCl + NaOH, NaCl only or NaOH only at two different concentrations, without the addition of any copper salts. CuO crystalline structures with limited impurities (e.g. Cu and Cu(OH)2phases) were produced from NaCl + NaOH containing solutions, mainly CuO and CuCl2structures were synthesized in the electrolyte solution containing only NaCl and no synthesis occurred in solutions containing only NaOH. Both aggregated and dispersed nanostructures were produced in the NaCl + NaOH and NaCl containing solutions. Reaction pathways leading to the formation of the nanostructures are proposed and discussed

Carrier extraction from metallic perovskite oxide nanoparticles

This work was supported by EPSRC (EP/K022237/1, EP/M024938/1 and EP/R023638/1), the EPSRC Supergen SuperSolar Hub, the Department for Employment and Learning (DEL) of Northern Ireland Studentship, and by the New Energy and Industrial Technology Development Organization (NEDO).We observe the extraction of carriers excited between two types of bands in the perovskite oxide, Sr-deficient strontium niobate (Sr0.9NbO3). Sr0.9NbO3 exhibits metallic behaviour and high conductivity, whilst also displaying broad absorption across the ultraviolet, visible, and near-infrared spectral regions, making it an attractive material for solar energy conversion. Furthermore, the optoelectronic properties of strontium niobate can easily be tuned by varying the Sr fraction or through doping. Sr-deficient strontium niobate exhibits a split conduction band, which enables two types of optical transitions: intraband and interband. However, whether such carriers can be extracted from an unusual material as such remains unproven. In this report, we have overcome the immense challenge of photocarrier extraction by fabricating an extremely thin absorber layer of Sr0.9NbO3 nanoparticles. These findings open up great opportunities to harvest a very broad solar spectral absorption range with reduced recombination losses.Publisher PDFPeer reviewe

Ultra‐small CuO nanoparticles with tailored energy‐band diagram synthesized by a hybrid plasma‐liquid process

CuO is a versatile p-type material for energy applications capable of imparting diverse functionalities by manipulating its band-energy diagram. We present ultra-small quantum confined cupric oxide nanoparticles (CuO NPs) synthesized via a simple one-step environmentally friendly atmospheric pressure microplasma synthesis process. The proposed method, based on the use of a hybrid plasma-liquid cell, enables the synthesis of CuO NPs directly from solid metal copper in ethanol with neither surfactants nor reducing agents. CuO NPs films are then used for the first time in all-inorganic third generation solar cell devices demonstrating highly effective functionalities as blocking layer

Varying Surface Chemistries for p‑Doped and n‑Doped Silicon Nanocrystals and Impact on Photovoltaic Devices

Doping of quantum confined nanocrystals offers unique opportunities to control the bandgap and the Fermi energy level. In this contribution, boron-doped (p-doped) and phosphorus-doped (n-doped) quantum confined silicon nanocrystals (SiNCs) are surface-engineered in ethanol by an atmospheric pressure radio frequency microplasma. We reveal that surface chemistries induced on the nanocrystals strongly depend on the type of dopants and result in considerable diverse optoelectronic properties (e.g., photoluminescence quantum yield is enhanced more than 6 times for n-type SiNCs). Changes in the position of the SiNCs Fermi levels are also studied and implications for photovoltaic application are discussed