Mwenya Trevor

Dual function interfacial layer for highly efficient and stable lead halide perovskite solar cells

The trap states and the intrinsic nature of polycrystalline organometallic perovskites cause carrier losses in perovskite solar cells (PSCs) through carrier recombination at the surface and subsurface of the perovskites, leading to lowered conversion efficiency. Herein, to reduce the carrier losses, an intelligent approach concerning surface passivation and interfacial doping of the perovskite is proposed by introducing an F4TCNQ interfacial layer. The trap states at the perovskite surface are efficiently suppressed, leading to a homogenous surface potential of perovskite, which avoids the surface carrier recombination. The Fermi level of the perovskite is shifted to its valence band by 0.2 eV, inducing an energy barrier for electron diffusion and contributing directly to a minimized carrier recombination at the subsurface of the perovskite film. Consequently, the performance of the PSCs is remarkably improved, with the average efficiency increased from 14.3 ± 0.9% to 16.4 ± 1.0% (with a maximum efficiency of 18.1%). Moreover, the PSCs with the dual function interfacial layer show enhanced long-term stability in ambient air without device encapsulation.

A one-step template-free approach to achieve tapered silicon nanowire arrays with controllable filling ratios for solar cell applications

A facile and low-cost one-step template-free approach is presented for the fabrication of tapered silicon nanowire (SiNW) arrays. A silver network catalyst is used to chemically etch silicon in a HF/H2O2 solution, where the solution is chosen to selectively dissolve the silver network during the etching process, resulting in the formation of tapered SiNWs. Notably, the filling ratio of the tapered SiNWs can be tuned simply by varying the pattern of the silver network. Surface reflection was strongly suppressed in the tapered SiNW arrays (only 400 nm in thickness), which were employed in SiNWs/poly(3,4-ethylenedioxy-thiophene):poly(styrenesulfonate) (PEDOT:PSS) heterojunction solar cells exhibiting a power conversion efficiency of 6.7%. The tapered SiNW arrays prepared by this one-step template-free method are expected to be efficient structures for a variety of photovoltaic devices.

Ordering Ag nanowire arrays by spontaneous spreading of volatile droplet on solid surface

Large-area Ag nanowires are ordered by spontaneous spreading of volatile droplet on a wettable solid surface. Compared with other nanowires orientation methods, radial shaped oriented Ag nanowires in a large ring region are obtained in an extremely short time. Furthermore, the radial shaped oriented Ag nanowires are transferred and aligned into one direction. Based on the hydrodynamics, the coactions among the microfluid, gravity effect and the adhesion of substrate on the orientation of the Ag nanowires are clearly revealed. This spreading method opens an efficient way for extreme economic, efficient and “green” way for commercial producing ordered nanowire arrays.

The application of localized surface plasmons resonance in Ag nanoparticles assisted Si chemical etching

Localized surface plasmons excited by Ag nanoparticles are introduced in the chemical etching process of silicon. A special crateriform structure with gradually varying radius is achieved by the surface electromagnetic field enhancement effect of localized surface plasmons resonance (LSPR). Theoretical analysis demonstrates that the formation kinetics of the crateriform structures conforms to the local electromagnetic field enhancement and forward scattering induced by LSPR. The LSPR assisted photocatalytic etching offers a potential approach for the preparation of the surface microstructures used in optoelectronic devices.

Facile one-pot synthesis of flower-like AgCl microstructures and enhancing of visible light photocatalysis.

Flower-like AgCl microstructures with enhanced visible light-driven photocatalysis are synthesized by a facile one-pot hydrothermal process for the first time. The evolution process of AgCl from dendritic structures to flower-like octagonal microstructures is investigated quantitatively. Furthermore, the flower-like AgCl microstructures exhibit enhanced ability of visible light-assisted photocatalytic degradation of methyl orange. The enhanced photocatalytic activity of the flower-like AgCl microstructure is attributed to its three-dimensional hierarchical structure exposing with [100] facets. This work provides a fresh view into the insight of electrochemical process and the application area of visible light photocatalysts.

Exact comprehensive equations for the photon management properties of silicon nanowire.

Unique photon management (PM) properties of silicon nanowire (SiNW) make it an attractive building block for a host of nanowire photonic devices including photodetectors, chemical and gas sensors, waveguides, optical switches, solar cells, and lasers. However, the lack of efficient equations for the quantitative estimation of the SiNW’s PM properties limits the rational design of such devices. Herein, we establish comprehensive equations to evaluate several important performance features for the PM properties of SiNW, based on theoretical simulations. Firstly, the relationships between the resonant wavelengths (RW), where SiNW can harvest light most effectively, and the size of SiNW are formulized. Then, equations for the light-harvesting efficiency at RW, which determines the single-frequency performance limit of SiNW-based photonic devices, are established. Finally, equations for the light-harvesting efficiency of SiNW in full-spectrum, which are of great significance in photovoltaics, are established. Furthermore, using these equations, we have derived four extra formulas to estimate the optimal size of SiNW in light-harvesting. These equations can reproduce majority of the reported experimental and theoretical results with only ~5% error deviations. Our study fills up a gap in quantitatively predicting the SiNW’s PM properties, which will contribute significantly to its practical applications.

Research Progress of Solar Cells Based on Organic–Inorganic Hybrid Perovskites Methylamine Lead Halide

Methylamine lead halide is a kind of perovskite structural crystalline materials compounded by organic methylamine and inorganic lead halide, which has attracted great attention in photovoltaic research. Solution processed photovoltaics incorporating methylamine lead halide perovskite absorbers have achieved efficiencies of nearly 16% in solid-state device configurations, superseding traditional dye sensitized solar cells, evaporated and tandem organic solar cells, as well as various thin film photovoltaic. Now, interest has been soaring in this research domain, resulting in more and more controversies that related to the promotion and development of resulting photovoltaic devices. Therefore it is urgent and important to clarify the operating mechanism of such perovskite-based solar cells for their further development. In this rogress Report, we introduced the structure and preparation of organic–inorganic hybrid perovskite methylamine lead halide, and reviewed its latest investigation in solar cell application. Meanwhile, comparative analysis of some different views and key issues such as materials selection, device architecture etc. have been done.

Broadband antireflection property of silicon nanocone arrays with porous sidewalls fabricated by Ag-catalyzed etching

Siliconnanocone (SiNC) arrays with porous sidewallswere successfully fabricated through a simple, low-cost Ag-catalyzed etching method. By electron spin resonance technique and TEM analysis, it has been verified that the formation of porous SiNC arrays is due to the gradual dissolution of the pristine Ag nanoislands as they sank into the Si and the lateral etching of the regenerated Ag nanoparticles to the SiNC sidewalls. Theoretical calculation results suggest that the reflectance of the porous SiNC arrays is much lower than that of the smooth SiNC arrays over wide wavelengths ranging from 300nm to 1700nm. The long-wavelength reflectance can be further suppressed by increasing surface porosity of the SiNCs and their length. Experimental test results show the lowest average reflectance of 1.7% in the wavelength range of 300-1000nm while approximately 30% in the wavelength ranges of 1200-1700nm, which is generally consistent with the theoretical results. This shows that the porous SiNC arrays had excellent...