Interfacial Kinetics and Ionic Diffusivity of the Electrodeposited MoS₂ Film

The transition-metal disulfide (MoS2) is a fantastic material used in diverse fields of applications. Ionic diffusivity and interfacial exchange current density are model parameters that play a crucial role for the optimization of device performances, which are not clearly known for this material. The additive-free dense film of MoS2 has been deposited by a facile electrodeposition approach and characterized by structural, morphological, and compositional analyses. This report provides the characterization of interfacial charge-transfer kinetics and diffusion of lithium ion in the MoS2 films as a function of lithium concentration at 25 °C temperature. The interfacial exchange current density is observed to be varied barely, ∼0.069–0.066 mA/cm2, with the change of lithium content, from x = 0.01–0.25, in LixMoS2. The ionic diffusivity of the film is found to be in the range of ∼3 × 10–11–10–11 cm2 s–1 and does not vary much with the measured lithium concentration window. The electrochemical performances of the material are limited by the transport of lithium ion and interfacial kinetics over the measured state of lithium content. A submicron-size particle with high surface area is needed to be used as an electrode of the material for practical C-rates

Ecofriendly and Nonvacuum Electrostatic Spray-Assisted Vapor Deposition of Cu(In,Ga)(S,Se)₂ Thin Film Solar Cells

Chalcopyrite Cu­(In,Ga)­(S,Se)₂ (CIGSSe) thin films have been deposited by a novel, nonvacuum, and cost-effective electrostatic spray-assisted vapor deposition (ESAVD) method. The generation of a fine aerosol of precursor solution, and their controlled deposition onto a molybdenum substrate, results in adherent, dense, and uniform Cu­(In,Ga)­S₂ (CIGS) films. This is an essential tool to keep the interfacial area of thin film solar cells to a minimum value for efficient charge separation as it helps to achieve the desired surface smoothness uniformity for subsequent cadmium sulfide and window layer deposition. This nonvacuum aerosol based approach for making the CIGSSe film uses environmentally benign precursor solution, and it is cheaper for producing solar cells than that of the vacuum-based thin film solar technology. An optimized CIGSSe thin film solar cell with a device configuration of molybdenum-coated soda-lime glass substrate/CIGSSe/CdS/i-ZnO/AZO shows the photovoltaic (<i>j–V</i>) characteristics of <i>V</i>_oc = 0.518 V, <i>j</i>_sc = 28.79 mA cm^–2, fill factor = 64.02%, and a promising power conversion efficiency of η = 9.55% under simulated AM 1.5 100 mW cm^–2 illuminations, without the use of an antireflection layer. This demonstrates the potential of ESAVD deposition as a promising alternative approach for making thin film CIGSSe solar cells at a lower cost

Carrier Generation and Collection in CdS/CdSe-Sensitized SnO₂ Solar Cells Exhibiting Unprecedented Photocurrent Densities

CdS/CdSe-sensitized nanostructured SnO2 solar cells exhibiting record short-circuit photocurrent densities have been fabricated. Under simulated AM 1.5, 100 mW cm−2 illumination, photocurrents of up to 17.40 mA cm−2 are obtained, some 32% higher than that achieved by otherwise identical semiconductor-sensitized solar cells (SSCs) employing nanostructured TiO2. An overall power conversion efficiency of 3.68% has been achieved for the SnO2-based SSCs, which compares very favorably to efficiencies obtained by the TiO2-based SSCs. The characteristics of these SSCs were studied in more detail by optical measurements, spectral incident photon-to-current efficiency (IPCE) measurements, and impedance spectroscopy (IS). The apparent conductivity of sensitized SnO2 photoanodes is apparently too large to be measured by IS, yet for otherwise identical TiO2 electrodes, clear electron transport features could be observed in impedance spectra, tacitly implying slower charge transport in TiO2. Despite this, electron diffusion length measurements suggest that charge collection losses are negligible in both kinds of cell. SnO2-based SSCs exhibit higher IPCEs compared with TiO2-based SSCs which, considering the similar light harvesting efficiencies and the long electron diffusion lengths implied by IS, is likely to be due to a superior charge separation yield. The resistance to charge recombination is also larger in SnO2-based SSCs at any given photovoltage, and open-circuit photovoltages under simulated AM 1.5, 100 mW cm−2 illumination are only 26−56 mV lower than those obtained for TiO2-based SSCs, despite the conduction band minimum of SnO2 being hundreds of millielectronvolts lower than that of TiO2

15% Efficiency Ultrathin Silicon Solar Cells with Fluorine-Doped Titanium Oxide and Chemically Tailored Poly(3,4-ethylenedioxythiophene):Poly(styrenesulfonate) as Asymmetric Heterocontact

In order to achieve a high performance-to-cost ratio to photovoltaic devices, the development of crystalline silicon (c-Si) solar cells with thinner substrates and simpler fabrication routes is an important step. Thin-film heterojunction solar cells (HSCs) with dopant-free and carrier-selective configurations look like ideal candidates in this respect. Here, we investigated the application of n-type silicon/poly­(3,4-ethylenedioxythiophene):poly­(styrenesulfonate) (PEDOT:PSS) HSCs on periodic nanopyramid textured, ultrathin c-Si (∼25 μm) substrates. A fluorine-doped titanium oxide film was used as an electron-selective passivating layer showing excellent interfacial passivation (surface recombination velocity ∼10 cm/s) and contact property (contact resistivity ∼20 mΩ/cm2). A high efficiency of 15.10% was finally realized by optimizing the interfacial recombination and series resistance at both the front and rear sides, showing a promising strategy to fabricate high-performance ultrathin c-Si HSCs with a simple and low-temperature procedure