Unraveling the cause of degradation in Cu(In,Ga)Se ₂ photovoltaics under potential induced degradation

Abstract: Copper indium gallium diselenide (CIGS) based technology is actively competing in the global photovoltaic market with high conversion efficiency. Commercial CIGS modules are anticipated to perform on rated output in the field condition for 20 years. Potential induced degradation (PID) is considered as one of the critical concerns among all the current reliability assessment issues. PID accelerated tests have been performed on pre‐commercial CIGS modules to investigate reduction in electrical performance. We report the severe reduction in electrical performance after PID is correlated to the microstructural and chemical properties of the constituent materials. Under extreme PID stress, the cell surface reveals various defects including crater formation. The aim of this article is to explore the consequences of PID induced craters on the efficiency of CIGS solar cells by investigating material degradation kinetics. In this perspective, we present the root cause of PID in CIGS thin‐film modules in relation to microstructural defects by detailed investigation using J‐V analysis, field emission scanning electron microscope (FESEM), Raman spectroscopy, X‐Ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy (PL). This analysis can provide more effective and sustainable research strategies to cultivate more efficient and reliable CIGS technologies in the long run

Bidisperse silica nanoparticles close-packed monolayer on silicon substrate by three step spin method

We present the studies on the structural properties of monolayer Bidisperse silica (SiO2) nanoparticles (BDS) on Silicon (Si-100) substrate using spin coating technique. The Bidisperse silica nanoparticle was synthesised by the modified sol-gel process. Nanoparticles on the substrate are generally assembled in non-close/close-packed monolayer (CPM) form. The CPM form is obtained by depositing the colloidal suspension onto the silicon substrate using complex techniques. Here we report an effective method for forming a monolayer of bidisperse silica nanoparticle by three step spin coating technique. The samples were prepared by mixing the monodisperse solutions of different particles size 40 and 100 nm diameters. The bidisperse silica nanoparticles were self-assembled on the silicon substrate forming a close-packed monolayer film. The scanning electron microscope images of bidisperse films provided in-depth film structure of the film. The maximum surface coverage obtained was around 70-80%.by Sakshum Khanna, Priyanka Marathey, Utsav, Harsh Chaliawala, and Indrajit Mukhopadhya

Systematic investigation of close-packed silica nanospheres monolayer under sintering conditions

In this paper, we have quantified and investigated the effect of various sintering temperature on close-packed Silica Nanospheres (SNs) monolayers. SNs with diameters of 140, 175 and 220 nm were fabricated by an effective and reliable spin-coating technique. The fabricated SNs monolayers were sintered up to 1200 °C and were analyzed from FESEM to investigate in details for local and extended transformations in their structural and morphological properties. A distinct "neck-formation" was observed and was quantified with different particle size distribution as well as surface packing density. It was observed that SNs monolayer undergoes intra-particle reformation in the form of shrinkage in individual SNs and compactification of growth domains, followed by inter-particle sintering. A geometrical model was developed to determine the curvature radius and interpenetration depth thus enabling us to quantify the parameters that dominate the dynamics of the sintering process for such non-porous SNs.by Sakshum Khanna, Utsav Harsh Chaliyawala, Sagar Paneliya, Debmalya Roy, Kingsuk Mukhopadhyay, Rupak Banerjee and Indrajit Mukhopadhya

Fabrication of long-ranged close-packed monolayer of silica nanospheres by spin coating

In light of the importance of nanostructured surfaces for various technological applications, it becomes imperative to look for simple and reliable methods for assembling ordered nanostructures over a large area. Several methods have been employed for fabricating nanostructured surfaces but not many are compatible with large-scale fabrication. Here we demonstrate the fabrication of long-range ordered close-packed monolayer of silica nanospheres (SNs) (size approximately 200 nm) deposited on a silicon substrate by a three-step spin coating technique in atmospheric conditions, which could be realized on a very small time scale but has significant potential in numerous applications. The dispersity of the SNs and the influence of various deposition parameters like surface modification, SNs concentration, spin speed, spinning time and the volume of aliquot spread over the silicon substrate were studied to optimize uniform high surface coverage of the film. A relatively uniform monolayer film and high surface coverage of silica particles ranging from 85 to 90% were achieved by optimizing the above deposition parameters. These nanostructures templates can be used in the formation non-close-packed monolayer facilitating further development of ordered nanowires, which highlights the prospect of this approach as a simple preparation method for ordered arrays of nanospheres. We conclude that this method is highly suitable for industrial applications, because of faster and effective rate of production and scalability.by Sakshum Khannaa, Utsavb, Priyanka Maratheya, Harsh Chaliyawalaa, Narasimman Rajarama, Debmalya Royc, Rupak Banerjeeb and Indrajit Mukhopadhya

Improved mechanical performance and structural properties of bias induced reactively sputtered Si doped TiAlC nanocomposite coatings

Si doped TiAlC nanocomposite coatings consisting of nanocrystallineTiC phase embedded in amorphous matrix of a-C/a-Si/a-Al4C3 have been deposited on stainless steel and silicon (100) substrates using four cathode reactive unbalanced direct current magnetron sputtering at Tsub= 300οC. The effects of substrate bias ǀVbǀon the microstructure, surface morphological, compositional, mechanical and frictional properties have been carried out by using X-ray diffraction (XRD), field-emission scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, nanoindentation hardness tester and nano-scratch measurements. XRD analysis reveals that the coating exhibits fccNaCl type TiC (111) preferential orientations. Moreover, micro-Raman spectroscopy study indicates the existence of graphitic rich layer of a-C in the coating as the bias voltage increases. Substrate bias causes a subsequent change in the microstructure from fine granular to a denser morphology. High rate of ion bombardment induces a transformation from columnar to a non-columnar microstructure as the bias voltage increases. Coatings prepared at an optimum ǀVbǀ=50 V, exhibit the excellent hardness and Young’ modulus value of ~ 33 and 280 GPa, respectively. The friction co-efficient measurements show a decrease from ~ 0.55 to 0.24 as the bias voltage increases from ǀVbǀ= 25 to 150 V

Direct-synthesis of AgxCu100-x bimetallic nanoparticles on p-Si supports for the photoelectrochemical reduction of CO2

International audienc

Role of nanowire length on the performance of a self-driven NIR photodetector based on mono/bi-layer graphene (camphor)/SinanowireSchottky junction

International audienceIn this article, we have demonstrated a solid carbon source such as camphor as a naturalprecursor to synthesize a large area mono/bi-layer graphene (MLG) sheet to fabricate a nanowirejunction-based near infrared photodetectors (NIRPDs). In order to increase the surface-tovolumeratio, we have developed Si-nanowire arrays (SiNWAs) of varying lengths by etchingplanar Si. Then, the camphor-based MLG/Si and MLG/SiNWAs Schottky junctionphotodetectors have been fabricated to achieve an efficient response with self-driven propertiesin the near infrared (NIR) regime. Due to a balance between light absorption capability andsurface recombination centers, devices having SiNWAs obtained by etching for 30 min shows abetter photoresponse, sensitivity and detectivity. Fabricated NIRPDs can also be functioned asself-driven devices which are highly responsive and very stable at low optical power signals upto 2 V with a fast rise and decay time of 34/13 ms. A tremendous enhancement has beenwitnessed from 36 μAW−1 to 22 mAW−1 in the responsivity at 0 V for MLG/30 min SiNWAsthan planar MLG/Si PDs indicating an important development of self-driven NIRPDs based oncamphor-based MLG for future optoelectronic devices

Metal-Assisted Chemical Etching for the Direct Synthesis of Bimetallic Cu-Pd Nanoparticles on Silicon

An original study is presented for the synthesis of Cu100-xPdx nanoparticles directly on silicon by Metal Assisted Chemical Etching (MACE). CuPd is chosen as a representative bimetallic system on account of its interest and potential applications in catalysis and electrocatalysis, among others. The proposed methodology allows precise control of the nanoparticle bimetallic composition and structure. Thus, we demonstrate that Cu100-xPdx solid solutions and phase-separated nanoparticles can be synthesized at will by simply changing the deposition conditions. In-depth physical characterization of the synthesized material (structure, morphology, composition, oxidation state and d-band center position) is carried out by XRD, SEM-EDX and XPS. Finally, band bending simulations at the nanoscale in combination with electrochemical measurements help to interpret some of the peculiarities of the Pd, Cu and CuxPd100-x deposits. The new method can be easily implemented, used for various silicon substrate geometries and extended to any bimetallic system whose metals are suitable for MACE of silicon