Two-step Deposition Approach Research Articles

Coating of CoS on hybrid anode electrode with enhance performance in hybrid dye-sensitized solar cells

Improvement of the power generation performance of dye-sensitized solar cells (DSSCs) remains a key task, as charge transfer and charge separation are efficiently achieved at the photoanode and between the polysulfide electrolyte interface and the counter-electrode. We synthesized the metal sulfides from dithiocarbamate complexes and used them to fabricate a new modified cell by passivating the photoanode electrode with CoS nanoparticles and SnS as photosensitizer in a two-step deposition approach. They were used as FTO-TiO2/CoS/SnS/HI-30/FTO-Pt, known as C-S-1, C-S-2 and C-S-3. SEM images show that the C-S-1 and C-S-2 are uniform, without cracks and have a dense surface morphology covering the surface area. Thus, confirming the successively passivation by CoS and sensitization of SnS, forming FTO-TiO2/CoS/SnS heterostructure. The η of 8.79% and 9.43% are much higher than that of C-S-2, with 0.23% affirm the roles of the Co, Sn and S ratio on both devices. The EIS Nyquist plot for the C-S-2 device shows a semicircle radius smaller than the C-S-1 and C-S-3, which indicates more efficient inhibition of electron/hole pairs and faster transportation of photogenerated charge carriers. The enhanced performance of both devices shows that the passivation of the electrodes ensures that maximum absorption is achieved through a higher absorption coefficient of SnS. Also, both devices reach a steady state within about 200–300 s and remain at the steady state current for a long duration for C-S-1 and C-S-3. The enhanced performance of both devices shows that the passivation of the electrodes ensures that maximum absorption is achieved through a higher absorption co-efficient of SnS.

(Invited) Development of High-Performance Tin Perovskite Solar Cells Via a Sequential Two-Step Deposition Approach

The performance of a tin-based perovskite solar cell (PSC) has undergone rapid progress in recent years but most high-performing devices were fabricated according to a traditional one-step method with the key anti-oxidizer or passivator treated as an additive in the perovskite precursor solution. Herein we present a sequential deposition procedure to passivate the surface of a hybrid mixed cationic perovskite with phenylhydrazinium halide (PHX, X = Cl, Br, I and SCN) dissolved in trifluoroethanol (TFE) solvent. TFE plays an important role not only to give PHX sufficient solubility but also to retain the tin-perovskite films intact for an effective surface passivation characterized by SEM, XRD, GIWAX, SIMS, XPS, UPS, c-AMF and TCSPC. A slow surface passivation was observed; the performance of the PHSCN device improved upon increasing the storage period to attain the best efficiency 13.5 % for a current-voltage scan in the forward bias direction. An inverted effect of hysteresis was observed in that the efficiency of the forward scan was greater than of the reverse scan. An ion-migration model due to the effect of PH surface passivation was proposed to account for the observed phenomena. Furthermore, High-performance tin-based PSC have been extensively explored using PEDOT:PSS as a hole-transport material (HTM) layer according to a one-step fabrication method. In the second part of the work we report tin-based PSC using the concept of a self-assembled monolayer (SAM) to modify the ITO surface with deposition in two steps; a traditional one-step method failed to produce a uniform tin perovskite layer on the ITO/SAM surface because of insufficient surface hydrophilicity. Herein we developed a preheating procedure to diminish effectively the amounts of hydroxyl groups and oxygen vacancies on the ITO surface for a uniform SAM to form, which has been characterized with X-ray photoelectron spectra. We found that the ITO substrate preheated at 400 °C gave the best device performance for an efficiency of power conversion attaining 6.5 % with excellent enduring stability in a glove box for ~1900 h without encapsulation. The present work thus provides a new direction for the development of HTM-free lead-free perovskite solar cells for their future up-scale production.

Thin-Film Deposition and Characterization of a Sn-Deficient Perovskite Derivative Cs2SnI6

In this work, we describe details of a two-step deposition approach that enables the preparation of continuous and well-structured thin films of Cs2SnI6, which is a one-half Sn-deficient 0-D perovskite derivative (i.e., the compound can also be written as CsSn0.5I3, with a structure consisting of isolated SnI64– octahedra). The films were characterized using powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), UV–vis spectroscopy, photoluminescence (PL), photoelectron spectroscopy (UPS, IPES, XPS), and Hall effect measurements. UV–vis and PL measurements indicate that the obtained Cs2SnI6 film is a semiconductor with a band gap of 1.6 eV. This band gap was further confirmed by the UPS and IPES spectra, which were well reproduced by the calculated density of states with the HSE hybrid functional. The Cs2SnI6 films exhibited n-type conduction with a carrier density of 6(1) × 1016 cm–3 and mobility of 2.9(3) cm2/V·s. While the computationally derived band str...

Thin-Film Preparation and Characterization of Cs3Sb2I9: A Lead-Free Layered Perovskite Semiconductor

Computational, thin-film deposition, and characterization approaches have been used to examine the ternary halide semiconductor Cs3Sb2I9. Cs3Sb2I9 has two known structural modifications, the 0-D dimer form (space group P63/mmc, no. 194) and the 2-D layered form (P3m1, no. 164), which can be prepared via solution and solid-state or gas-phase reactions, respectively. Our computational investigations suggest that the layered form, which is a one-third Sb-deficient derivative of the ubiquitous perovskite structure, is a potential candidate for high-band gap photovoltaic (PV) applications. In this work, we describe details of a two-step deposition approach that enables the preparation of large grain (>1 μm) and continuous thin films of the lead-free layered perovskite derivative Cs3Sb2I9. Depending on the deposition conditions, films that are c-axis oriented or randomly oriented can be obtained. The fabricated thin films show enhanced stability under ambient air, compared to methylammonium lead(II) iodide per...

Immobilization of trypsin in polyaniline-coated nano-Fe3O4/carbon nanotube composite for protein digestion

In this report, a four-component nanocomposite, trypsin-immobilized polyaniline-coated Fe3O4/carbon nanotube composite, was synthesized for highly efficient protein digestion. Fe3O4 was deposited by the chemical coprecipitation of Fe2+ and Fe3+ in an alkaline solution containing carbon nanotubes (CNTs) to prepare nano-Fe3O4/CNT composite. Subsequently, polyaniline (PA) was assembled on the Fe3O4/CNT composite by the in situ polymerization of aniline in the presence of trypsin to obtain trypsin-immobilized PA/Fe3O4/CNT nanocomposite. The novel 1D superparamagnetic biomaterial has been characterized by TEM, SEM, XRD, and magnetometric analysis. The feasibility and performance of the unique magnetic biomaterial have been demonstrated by the tryptic digestion of bovine serum albumin, myoglobin, and lysozyme within 5min. The digests were identified by MALDI-TOF MS with sequence coverages that were comparable to those obtained from the conventional in-solution tryptic digestion. The present biocomposite offers considerable promise for protein analysis due to its high magnetic responsivity and excellent dispersibility. It can be easily isolated from the digests with the aid of an external magnetic field. Because the enzyme-immobilized nanocomposite can be prepared by a simple two-step deposition approach at low cost, it may find a wide range of biological applications including proteome research.

Experimental study of nucleation and quality of CVD diamond adopting two-step deposition approach using MPECVD

Effects of the deposition conditions on quality and nucleation density of CVD diamond were investigated using a microwave plasma enhanced chemical vapor deposition (MPECVD) method with methane-hydrogen gas mixtures. Diamond films were deposited at pressures of 665–4000 Pa, temperatures of 660–950 °C, and methane concentrations of 0.5–5 vol.%. Deposited diamond films were characterized by scanning electron microscopy, field emission scanning electron microscopy, micro-Raman spectroscopy, and X-ray diffraction. Diamond quality and nucleation density significantly affected by the deposition pressure, substrate temperature, and methane concentration. The findings of this work were discussed in terms of the effects of deposition conditions on the plasma composition. A two-step deposition approach was applied to improve nucleation density and quality of CVD diamond films. Polycrystalline diamond films were grown using the two-step deposition process changing a combination of parameters in the two steps. Growth and quality of the deposited diamond films were improved altering the deposition pressure and substrate temperature in the two steps.

Effect of substrate temperature and ion bombardment on the formation of cubic boron nitride films: A two-step deposition approach

The influence of substrate temperature and ion bombardment on the formation of cubic boron nitride (c-BN) films has been examined with bias-assisted magnetron sputtering of h-BN for argon and nitrogen as the working gases. It is shown through a two-step deposition approach that higher substrate temperatures are required only to establish an appropriate h-BN base layer which is mandatory as a nucleation base for c-BN. For nitrogen as the working gas the energy of the bombarding ions can also be reduced after c-BN-nucleation. Hence, the conditions for the formation of c-BN films are more restrictive for the initial growth stage than for the later c-BN growth once the nucleation into c-BN has been established. Corresponding results for argon and nitrogen display characteristic differences which lead to the conclusion that the establishment of full BN surface stoichiometry is a key condition for c-BN growth.