oCVD PEDOT-Cl Thin Film Fabricated by SbCl₅ Oxidant as the Hole Transport Layer to Enhance the Perovskite Solar Cell Device Stability

Perovskite solar cells (PSCs) exhibit remarkable power conversion efficiency (PCE) but face limitations due to poor stability, restricting their practical applications. The commonly used hole transport layer, poly(3,4-ethylene dioxythiophene):polystyrene­sulfonate (PEDOT:PSS), suffers from inherent acidity that compromises PSCs device stability through detrimental interactions with the counter electrode and perovskite layer. This study explores the use of oxidative chemical vapor deposition (oCVD) with antimony pentachloride (SbCl5) as a liquid oxidant to fabricate stable, ultrathin, and highly conformal PEDOT thin films, presenting a promising alternative for the hole transport layer in PSCs. The oCVD PEDOT-Cl thin films, grown using liquid SbCl5 oxidant, demonstrate excellent optoelectronic properties, precise control over nanostructure, stability, and integration capabilities, making them a robust and efficient choice as a hole transport layer. Integration of oCVD PEDOT-Cl thin films as the hole transport layer in PSCs yields a remarkable PCE of 20.74%, surpassing the PCE of 16.53% obtained by spin-coated PEDOT:PSS thin films treated with the dimethyl sulfoxide (DMSO) polar solvent. Furthermore, PSCs incorporating oCVD PEDOT-Cl thin films demonstrate a notable 2.5× enhancement in stability compared to PEDOT:PSS-DMSO counterparts. Utilizing as-deposited oCVD PEDOT-Cl thin films fabricated using SbCl5 oxidant with highly conformal characteristics introduces opportunities for enhancing light absorption by the photoactive layer through artificially textured surfaces. This advancement opens up possibilities for the development of PSCs with high performance and enhanced stability

Intergrain Diffusion of Carbon Radical for Wafer-Scale, Direct Growth of Graphene on Silicon-Based Dielectrics

Graphene intrinsically hosts charge-carriers with ultrahigh mobility and possesses a high quantum capacitance, which are attractive attributes for nanoelectronic applications requiring graphene-on-substrate base architecture. Most of the current techniques for graphene production rely on the growth on metal catalyst surfaces, followed by a contamination-prone transfer process to put graphene on a desired dielectric substrate. Therefore, a direct graphene deposition process on dielectric surfaces is crucial to avoid polymer-adsorption-related contamination from the transfer process. Here, we present a chemical-diffusion mechanism of a process for transfer-free growth of graphene on silicon-based gate-dielectric substrates via low-pressure chemical vapor deposition. The process relies on the diffusion of catalytically produced carbon radicals through polycrystalline copper (Cu) grain boundaries and their crystallization at the interface of Cu and underneath silicon-based gate-dielectric substrates. The graphene produced exhibits low-defect multilayer domains (<i>L</i>_a ∼ 140 nm) with turbostratic orientations as revealed by selected area electron diffraction. Further, graphene growth between Cu and the substrate was 2-fold faster on SiO₂/Si­(111) substrate than on SiO₂/Si­(100). The process parameters such as growth temperature and gas compositions (hydrogen (H₂)/methane (CH₄) flow rate ratio) play critical roles in the formation of high-quality graphene films. The low-temperature back-gating charge transport measurements of the interfacial graphene show density-independent mobility for holes and electrons. Consequently, the analysis of electronic transport at various temperatures reveals a dominant Coulombic scattering, a thermal activation energy (2.0 ± 0.2 meV), and two-dimensional hopping conduction in the graphene field-effect transistor. A band overlapping energy of 2.3 ± 0.4 meV is estimated by employing the simple two-band model

Plasma-Corona-Processed Nanostructured Coating for Thermoregulative Textiles

A rapid increase in the atmospheric temperature has been reported in recent years worldwide. The lack of proper aid to protect from exposure to the sun during working hours has raised the number of sunburn cases among workers. It is important to promote productive workplaces without compromising safety and health concerns. In the present work, we report the low-temperature plasma (LTP)-assisted tailoring of the surface properties of fabrics to reflect IR radiation from the sun. The LTP technique can be adapted for thermally sensitive materials such as fabrics and textiles due to its lower working temperature range of 30 °C. We have modified various substrates such as commercially available fabric, regular, and boron nitride-incorporated electrospun PET surfaces with tetraethoxy orthosilicate (TEOS) plasma. TEOS plasma treatment can deposit a reactive plasma-polymerized silane nanolayer on the surface of these substrates. The plasma-processed silane nanolayer was systematically characterized using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy, Keyence 3D-microscopic imaging, and transmission electron microscopy (TEM). From the SEM and TEM data, the size of the nanoparticles was observed in the range 100–200 nm. The thermal regulation coating thickness was examined with a Keyence 3D imaging technique. The IR reflection potential of the surface was analyzed by using an FLIR thermal imaging system. The data revealed that the plasma-modeled nanosurface shows higher reflective potential toward IR rays, and it seems to be cooler than the unprocessed surface by approximately 15 °C. The stability and efficiency of the plasma-modified electrospun nanolayer in water were satisfactorily examined with SEM and IR imaging. Taken together, these results suggest the excellent potential of plasma processing to develop IR reflective coatings

Retained Carrier-Mobility and Enhanced Plasmonic-Photovoltaics of Graphene via ring-centered η⁶ Functionalization and Nanointerfacing

Binding graphene with auxiliary nanoparticles for plasmonics, photovoltaics, and/or optoelectronics, while retaining the trigonal-planar bonding of sp² hybridized carbons to maintain its carrier-mobility, has remained a challenge. The conventional nanoparticle-incorporation route for graphene is to create nucleation/attachment sites via “carbon-centered” covalent functionalization, which changes the local hybridization of carbon atoms from trigonal-planar sp² to tetrahedral sp³. This disrupts the lattice planarity of graphene, thus dramatically deteriorating its mobility and innate superior properties. Here, we show large-area, vapor-phase, “ring-centered” hexahapto (η⁶) functionalization of graphene to create nucleation-sites for silver nanoparticles (AgNPs) without disrupting its sp² character. This is achieved by the grafting of chromium tricarbonyl [Cr­(CO)₃] with all six carbon atoms (sigma-bonding) in the benzenoid ring on graphene to form an (η⁶-graphene)­Cr­(CO)₃ complex. This nondestructive functionalization preserves the lattice continuum with a retention in charge carrier mobility (9% increase at 10 K); with AgNPs attached on graphene/n-Si solar cells, we report an ∼11-fold plasmonic-enhancement in the power conversion efficiency (1.24%)