Photo-induced CdS nanoparticles growth

A photochemical approach on the size control of CdS nanoparticles is presented. CdS nanoparticles were grown using the photo-induced reaction of sodium thiosulfate with Cadmium sulfate, in the absence of any surfactant. Particles of 5.5–11 nm were obtained by changing the illumination time. The dark growth of nanoparticles was negligible, however we found by optical scattering measurements that a ripening phenomenon occurs and the size of nanoparticles slightly increases with time.     

Hybrid solar cell based on polythiophene and GaN nanoparticles composite

Hybrid solar cells based on poly(3-hexylthiophene)(P3HT)and Galium nitride(GaN)nanoparticle bulk heterojunction are fabricated and analyzed.The GaN nanocrystal is synthesized by means of a combination of sol–gel process with high temperature ammoniation using Ga(OC2H5)as a precursor.Their characteristics are determined by X-ray diffraction,X-ray photoelectron spectroscopy,and scanning electron microscopy.With the addition of GaN nanoparticle to P3HT,the device performance is greatly enhanced.     

Exploring alkylthiol additives in PBDB-T:ITIC blended active layers for solar cell applications

Bulk heterojunction, non-fullerene PBDB-T:ITIC blend polymer solar cells have been fabricated. The active layers consisting of PBDB-T as a donor and ITIC as an acceptor are optimized using a series of alkylthiol additives(1,3-propanedithiol, 1,4-butanedithiol, and 1,8-octanedithiol). It is found that the donor and acceptor are phase separated with different crystalline domains. The additives effectively re-organize the morphology and extend the molecule ordering in lamellar structure with increased correlation length in ITIC domain, benefiting the generation and dissociation of exciton and reducing charge recombination. A substantial improvement in power conversion efficiency of the devices from 8.13% to 9.44% is observed. This study shows that the application of alkylthiol additives is a simple and effective approach to improve the device performance in solar cells based on polymer/non-fullerene blend system.     

给体-受体型有机太阳电池光敏层的优化设计

针对有机给体-受体型异质结薄膜太阳电池，基于薄膜中的光学干涉效应和激子扩散理论建立模型，定量分析了有机层厚度对太阳电池性能的影响，通过限制有机光敏层厚度来控制由光学干涉效应引起的局部光子密度(光强度)的分布，进而优化有机层的吸收效率和激子扩散效率，以此达到提高器件光伏效率的目的.并通过实验进行了验证. 关键词： 有机太阳电池 给体-受体 优化设计 激子     

Simplistic surface active agents mediated morphological tweaking of CdS thin films for photoelectrochemical solar cell performance

This study reports on the formation of cadmium sulfide (CdS) nanostructures with controlled morphology synthesized via a simple chemical route in surface active agent environment. The effect of organic surface active agents (surfactants) as sodium dodecyl sulfate (SDS), polyethylene glycol (PEG) and cetyltrimethylammonium bromide (CTAB) on structural, morphological, optical and photoelectrochemical properties of CdS thin films have been studied. Our results reveal that the organic surfactants play key roles in tweaking the surface morphology. A compact spongy ball like morphology was observed for the CdS samples grown without organic surfactants. The cauliflower's with nanopetals from the CTAB, whereas crowded star fish like morphology is observed in PEG-mediated growth. Water hyacinth like morphology is tweaked using SDS. Considering the importance of these nanostructures, the growth mechanism has been discussed in details. Additionally, the samples are photoelectrochemically (PEC) active and having a compact surface with a nanoporous structure twig helps in improved photoelectrochemical performance compared to that of CdS deposits from surfactant free solution. This is a simplistic way to tune the morphology using surfactants, which can be applied to other energy conversion applications.     

True nature of active layers in organic solar cells fabricated by sequential casting of donor and acceptor layers

The operation characteristics of nominal bilayer (BL) organic solar cells (OSCs), the active layers (ALs) of which consisted of sequentially casted bottom P3HT donor and top ICBA acceptor layers, resembled those of OSCs with bulk heterojunction (BHJ) ALs. Optical analysis and device simulations showed that such resemblance can be attributed to a similarity in the micromorphology of ALs; as‐deposited BL‐type ALs transformed spontaneously into BHJ‐type ALs. The inclusion of P3HT nanowires (NWs) in the donor layers resulted in different AL micromorphology and consequently a larger power conversion efficiency. Separate assessment of the exciton generation and charge–carrier transport and/or extraction showed that the contribution of P3HT NWs was more prominent in optical effects.

     

In-situ growth of a CdS window layer by vacuum thermal evaporation for CIGS thin film solar cell applications

Highly crystalline and transparent CdS films are grown by utilizing the vacuum thermal evaporation （VTE） method. The structural, surface morphological, and optical properties of the films are studied and compared with those prepared by chemical bath deposition （CBD）. It is found that the films deposited at a high substrate temperature （200 ℃） have a preferential orientation along （002） which is consistent with CBD-grown films. Absorption spectra reveal that the films are highly transparent and the optical band gap values are found to be in a range of 2.44 eV-2.56 eV. Culnl_xGaxSe2 （CIGS） solar cells with in-situ VTE-grown CdS films exhibit higher values of Voc together with smaller values of Jsc than those from CBD. Eventually the conversion efficiency and fill factor become slightly better than those from the CBD method. Our work suggests that the in-situ thermal evaporation method can be a competitive alternative to the CBD method, particularly in the physical- and vacuum-based CIGS technology.     

In situ growth of silver nanoparticles in mesoporous silica by spray pyrolysis

Silver-dispersed mesoporous silica was in situ synthesized in aerosol phase. The solidification of silica was catalyzed in the presence of the silver, which increased the order and d values of the mesophase at given reactor temperature. Silver nanoparticles grew confined in the pores when the atomic % of silver to Si was below 10 and the pore wall turned to be impermeable above 400 °C. Silver permeated through the pore wall below 400 °C to grow freely in the carrier gas. The mesophase deteriorated using spray pyrolysis above 800 °C due to the further densification of silica, or above 10 at.% of silver due to the excessive growth within the phase. The highest dispersion of silver ~4 nm in diameter with the highest order of the mesoporosity was obtained at 600 °C with 5 at.% silver. Calcination following the spray pyrolysis further densified the silica phase to freeze the growth of silver particles as well as lower the d value of the mesophase.     

In situ synthesis of mesoporous CdS nanoparticles in ternary cubic phase lyotropic liquid crystal

An in situ technique for the synthesis of CdS nanoparticles in a ternary lyotropic cubic phase liquid crystal has been carried out. The extremely viscous cubic phase liquid-crystal system consists of poly(oxyethylene)₁₀ nonyl phenol ether as non-ionic surfactant, octane as oil phase and an aqueous phase containing reactant ions (Cd²⁺ and S^2-). Thioacetamide (TAA) has been utilized as a source for slow release of sulfur in the in situ synthesis of CdS. Rheological results show that CdS nanoparticle growth did not disrupt the structure of the cubic phase liquid-crystal system. This indicates that homogenous synthesis of CdS in the liquid crystal had been achieved. The final products were characterized using X-ray photoelectron spectroscopy, thermal gravimetric analysis, transmission electron microscopy and UV-visible spectroscopy. It was found that the CdS nanoparticles formed have a mesoporous structure with a size dependent on the TAA decomposition aging time. Received: 29 March 2002 / Accepted: 4 September 2002 / Published online: 17 December 2002 RID="*" ID="*"Corresponding author. Fax: +603-8921/3257, E-mail: shahidan@pkrisc.cc.ukm.my     

Electrical bistability of CdS nanoparticles sandwiched between aluminum tris (8-hydroxyquinoline) layers

We report the electrical bistability of cadmium sulfide (CdS) nanoparticles (NPs) capped by dodecanethiol, which are sandwiched between aluminum tris (8-hydroxyquinoline) (Alq₃) layers. The current density–voltage (J–V) characteristics of the device with Al/Alq₃/CdS NPs/Alq₃/Al structures show the high- and low-conducting state at the same voltage, and the two states are reproducible by applying different negative sweeping voltages. The Ohmic model and the space–charge limited model are proposed and supported by the current density–voltage results, which give a possible transport mechanism for the electrical bistability of our devices.     

CuInS2 solar cell absorber plasmonically modified by gold nanoparticles

Thin CuInS₂ light-absorbing layer prospective for the solar cell applications is modified by gold nanoparticles. Theoretical and experimental possibilities of placement nanoparticles over or under the CuInS₂ coating were tested. It was revealed that placement of nanoparticles under the CuInS₂ layer is better in terms of spray pyrolysis technique. It results in more effective plasmon-enhanced light absorption in the CuInS₂ layer at the visible/near infrared 650–700 nm spectral range.     

New issue of GaN nanoparticles solar cell

This study involves the synthesis of gallium nitride (GaN) nanoparticles (NPs) under different low temperatures using a simple chemical method. The nanoparticles are spin coated on Si substrate to fabricate the solar cell. The FESEM images obtained indicate the presence of cubic GaN nanoparticle with average diameter of 50 nm synthesized at 90 °C. The spin coating technique deposited n-GaN NPs/Si(111) produced a heterojunction solar cell with fill factor of 0.56 and conversion efficiency of 2.06%. Based on these results, this study proposes a novel low cost technique for the fabrication of GaN NPs solar cells.     

Comparison of CdS films deposited by different techniques: Effects on CdTe solar cell

Polycrystalline cadmium sulfide (CdS) thin-films were deposited on glass substrate by chemical bath deposition (CBD) and vacuum evaporation (VE) techniques. VE-CdS films consisted primarily of hexagonal phase, whereas CBD CdS films containing primarily the cubic form. VE-grown films were shown to have better crystallinity than CBD-grown films. The grain size of the CBD films is smaller than the ones of VE films. VE-CdS films exhibited relatively high transmittance in the above-gap region and band gap compared with CBD films. However, CdTe solar cells with these low quality CBD-CdS layers yield higher and more stable characteristics. Current-voltage-temperature measurements showed that the current transport for both cells was controlled by both tunneling and interface recombination but the cells with CBD-CdS displayed less tunneling.     

Plasmons in waveguide structures formed by two graphene layers

Plasmon modes in a waveguide formed by two parallel graphene layers with an insulator spacer layer are considered. The existence of TM and TE guided modes is predicted and their properties are compared with those of plasmons in metal/insulator waveguides.     

In situ characterization of nanoparticles during growth by means of white light scattering

A simple method of characterization of suspensions of spherical nanoparticles with monotonically variable size is proposed. It allows for the in situ measurement of the particle size as well as spectral dependence of their refractive indices. The method requires three optical channels: one for the illumination of a suspension by white light and two for the measurements of the spectra of scattered light. Parameters of the particles are determined by fitting the measured temporal spectral surfaces by the calculated Mie scattering functions. The method is applied to the particles being grown in a low-pressure reactive plasma of a discharge in an acetylene-argon mixture.     

Enhanced optical absorption by Ag nanoparticles in a thin film Si solar cell

Thin film solar cells have the potential to significantly reduce the cost of photovoltaics. Light trapping is crucial to such a thin film silicon solar cell because of a low absorption coefficient due to its indirect band gap. In this paper, we investigate the suitability of surface plasmon resonance Ag nanoparticles for enhancing optical absorption in the thin film solar cell. For evaluating the transmittance capability of Ag nanoparticles and the conventional antireflection film, an enhanced transmittance factor is introduced. We find that under the solar spectrum AM1.5, the transmittance of Ag nanoparticles with radius over 160 nm is equivalent to that of conventional textured antireflection film, and its effect is better than that of the planar antireflection film. The influence of the surrounding medium is also discussed.     

The structure of CdS nanoparticles

CdS nanoparticles in the high-pressure polyethylene (HPPE) matrix have been synthesized and investigated. Shift of the fundamental absorption edge has been shown to be absent with a variation in the nanoparticle size for the given samples and a small disordering of atoms in nanoparticles is observed.     

Preparation of chemically deposited thin films of CdS/PbS solar cell

The present paper reports the preparation of a solar cell which has a cross-sectional scheme: ITO/CdS/PbS, containing a commercially transparent conductive ITO; chemically deposited n-type CdS (340 nm) and absorbed layer of p-type PbS (1400 nm). The structural and optical properties of the constituent films are presented. X-ray diffraction showed that all of the thin films are polycrystalline. Using scanning electron microscopy, the present study revealed that the films have uniform surface morphology over the substrate. The solar cell was characterized by determining the open circuit voltage, short-circuit current density, and J–V under 40 mW/cm² solar radiation. The efficiency of the solar cells was 1.35%, which is much higher (0.041, 0.5 and 0.1–0.4%) and slightly smaller (1.65%) than some solar cells reported in the literature.