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Passivating electron‐transporting layers (ETLs) with alkali salts have demonstrated a facial approach that is essential in healing defective surfaces, consequently improving the functionality and stability of perovskite‐based solar cells (PSCs). Herein, the pseudohalide salt of sodium tetrafluoroborate, whose anions have a higher electronegativity than other halide salts (i.e., iodide and chloride), with the potential to passivate the surface of tin oxide while enhancing the optoelectronic properties of a perovskite film, is presented. Meanwhile, the density functional theory calculations show that BF4−/F− ions exhibit a robust ionic interaction with an uncoordinated Sn4+ site. In contrast, the Na ion is bound to an oxygen atom of the OH− group, which helps reduce surface defect states and improves charge transfer properties. Thus, the best PSC exhibits a current density of 23.51 mA cm−2, an open‐circuit voltage of 1.10 V, and an excellent fill factor of 80.48, providing an efficiency of 20.82%, which exceeds that of a control device (18.38%). Importantly, the retention of the power conversion efficiency on NaBF4‐based PSCs without encapsulation is 18.44% after 1000 h of aging under ambient conditions, whereas the retention of a control device is only 16.08%. [ABSTRACT FROM AUTHOR]

Posttreatment of titanium oxide (TiO2) using lithium (Li) and cobalt (Co) precursors is widely adopted to modify the charge quenching property in perovskite solar cells (PSCs); however, the fundamental understanding of the effect of the modification layer on the material itself and, consequently, the photovoltaic performance stability is not complete. In this work, in situ X‐ray diffraction measurements show that the Li and Co ions can diffuse into TiO2 and consequently accelerate the rutile phase transformation. X‐ray photoelectron spectroscopy results reveal the appearance of a Ti3+ feature in both the Li‐ and Co‐treated samples, suggesting that the treatment ions are partially located at the subsurface/surface of the spin‐cast TiO2 layer. The Li‐treated TiO2 exhibits greatly upshifted conduction band edges, which benefits charge extraction properties and improves the average device parameters in a complete PSC. To complement the experiments, density functional theory calculations are performed. While Li treatment initially results in enhanced electronic properties, Li‐treated TiO2 tends to have more surface vacancies over time and is more susceptible to adsorption and accumulation of iodide ions compared to the Co‐treated sample, which is experimentally supported by surface photovoltage spectroscopy and time‐resolved photoluminescence results. [ABSTRACT FROM AUTHOR]

Laser texturing process is a promising method to alter the wettability of metal surface on which micro/nano rough structures are created for changing the contact angle between the textured surface and liquid droplet. This paper aims at fabricating a superhydrophobic surface on AISI316L stainless steel, and a nanosecond pulse laser was employed for texturing line and point patterns on the metal surface. The influences of texturing patterns, laser power, scan speed, irradiation duration, and aging hours on the water contact angle and morphology of workpiece surface were investigated. According to the results, the hydrophilic surface was obtained right after the texturing process, and the surface turned to be hydrophobic after being left in ambient air for 15 days. The aging of laser-textured surface was also performed to induce the chemisorption of hydrocarbons toward the surface. This post process was able to shorten the hydrophilic-to-hydrophobic transition from days to a few hours. The aging duration of 2 and 0.5 h was respectively recommended for yielding and stabilizing the superhydrophobicity on line- and point-patterned surfaces. The maximum contact angle of 159.61° was achievable when the point pattern was textured on the stainless steel surface by using the laser power of 10 W and irradiation duration of 0.18 ms. [ABSTRACT FROM AUTHOR]

To analyze the dominant recombination, researchers often consider the diode ideality factor (nid), determined from the fitting of a semi‐log plot of light intensity–dependent open‐circuit voltage (Voc(lnI/I0)) to a linear dependence. This value is called "nid,Voc". Theoretically, nid is the exponential dependence factor in the recombination rate function of the split of quasi‐Fermi levels. This nid is called "nid,C". Herein, correlations between nid,Voc, nid,C, and the dominant recombination are reconsidered using a validated numerical drift–diffusion model and a diode current analysis in perovskite solar cell devices having accumulations of charged defects near the carrier transporting interfaces. It is found that the interplay between the recombination processes affects the linearity of the Voc(lnI/I0) plots. Devices having a single dominant recombination process exhibit Voc(lnI/I0) plots that appear to be linear, resulting in nid,Voc ≈ nid,C of the dominant recombination. Conversely, bends in the Voc(lnI/I0) curves indicate that different (multiple) recombination mechanisms dominate at different light intensities, so nid,Voc is an effective nid of the total diode current whose value is not consistent with any nid,C values. This work provides more understanding of nid and how to interpret a Voc(lnI/I0) curve more correctly for the insights into recombination mechanisms. [ABSTRACT FROM AUTHOR]

Polymer–polymer blends have been reported to exhibit exceptional thermal and ambient stability. However, power conversion efficiencies (PCEs) from devices using polymeric acceptors have been recorded to be significantly lower than those based on conjugated molecular acceptors. Herein, two organic nonfullerene bulk heterojunction (BHJ) blends ITIC:PBDB‐T and N2200:PBDB‐T, together with their fullerene counterpart, PCBM:PBDB‐T, are adopted to understand the effect of electron acceptors on device performance. Free charge carrier properties using time‐resolved microwave conductivity (TRMC) measurements are comprehensively investigated. The nonfullerene devices show an improved PCE of 10.06% and 6.65% in the ITIC‐ and N2200‐based cells, respectively. In comparison, the PCBM:PBDB‐T‐based devices yield a PCE of 5.88%. The optimal N2200:PBDB‐T produced the highest TRMC mobility, longest lifetime, and greatest free‐carrier diffusion length. It is found that such phenomena can be associated with the unfavorable morphology of the all‐polymer BHJ microstructure. In contrast, the solar cells using either the PCBM or ITIC acceptors display a more balanced donor and acceptor phase separation, leading to more efficient free‐carrier separation and transport in the operating device. By sacrificing efficiency for superior stability, it is shown that the improved structure in all‐polymer blend can deliver a more stable morphology under thermal stress. [ABSTRACT FROM AUTHOR]

A simple deposition process for preparing crystalline semiconductors with low degrees of disorder is of paramount interest for both device applications and research investigations. This study centers on the ultrasonically sprayedaerosol based approach for preparing crystals of methylammonium lead trihalide perovskite (CH3NH3PbI3). The surface photovoltage (SPV) spectra are found to depend strongly on the preparation conditions, with the SPV signals (below the material's band gap) providing information on the defect states. The measured values of tail states near the band gap (Et) are found to be about 21 and 52 meV for the CH3NH3PbI3 crystals prepared by the ultrasonically sprayed-on and spun casting approaches, respectively. [ABSTRACT FROM AUTHOR]

Results of a temperature dependence study of photoinduced charge separation across P3HT nanocrystals at P3HT/ITO interfaces have been investigated by modulated surface photovoltage (SPV) spectroscopy in a fixed capacitor arrangement. The SPV measurements were correlated with the crystalline sizes of P3HT nanocrystals determined by grazing incidence X-ray diffraction (GIXRD). The crystalline sizes of P3HT nanocrystals were varied systematically by progressive heating/cooling cycles identical for SPV and GIXRD measurements. Photovoltage signals, indication of photoinduced charge dissociation in space, at the P3HT/ITO interface were collected, and electrons were separated across the first monolayer of P3HT nanocrystals at the P3HT/ITO interface due to band bending. The activation energies for quenching of the in-phase and phase-shifted by 90° SPV signals were 0.7 and 0.6 eV, respectively. Thermal activation of the formation of P3HT nanocrystals was of the same order as the enthalpy of fusion of ideal crystals from regioregular P3HT. A schematic drawing of photoinduced charge separation at the P3HT/ITO is proposed. [ABSTRACT FROM AUTHOR]

Combined Experimental and Simulation Studies of Lithium and Cobalt-Modified TiO2 and Their Impacts on the Performance and Stability of Perovskite Solar Cells (Adv. Keywords: charge separation; density functional theory simulations; Li/Co-treatments; perovskite solar cells; surface photovoltage; TiO 2 EN charge separation density functional theory simulations Li/Co-treatments perovskite solar cells surface photovoltage TiO 2 1 1 1 11/07/22 20221101 NES 221101 B Photovoltaic Performance Stability b The most fundamental properties of photovoltaic materials are impacted by the photoinduced charge separation behavior, which can be improved by modifying the underlying layer that the perovskite is prepared on top. Charge separation, density functional theory simulations, Li/Co-treatments, perovskite solar cells, surface photovoltage, TiO 2. [Extracted from the article]

Organic halide perovskite solar cells (PSC's) have achieved high efficiencies in a relatively short amount of time. In order to attain efficiency in the neighborhood of the Shockley‐Queisser (SQ) limit, additional modifications are continuously being made. A simple lumped circuit model, which had been previously used to investigate organic and inorganic thin‐film solar cells, is used in this study to gain more insight into the effects of these modifications on the performance‐related factors. It is examined that the changes in the lumped‐circuit parameters associated with the device performances when different hole transport materials (HTM's) such as PEDOT:PSS, NiOx, and PTAA or when different underneath substrates are employed. The reason for this interest is the well‐accepted fact that the defect formation greatly hinders the formation of photo‐generated charge carriers. Using the time‐resolved surface photovoltage measurements, we show that the photo‐induced charge separation and charge migration are greatly influenced by the HTM's. The resulting changes were analyzed in detail. Unlike what occurs when CH3NH3PbI3 is deposited onto bare ITO or PEDOT:PSS, the long‐lived (from micro‐millisecond) charge separations are observed when the NiOx is used as the HTL. These observations point to the need to examine other low‐cost HLM's or combinations of them, for use to improve the solar energy conversion efficiencies of the PSC's. [ABSTRACT FROM AUTHOR]

The design and utilization of an affordable compact-size high-density plasma reactor for micro- and nano-crystalline diamond (MCD/NCD) thin film deposition is presented. The system is based on a 2.45 GHz domestic microwave oven magnetron. A switching power supply module, which yields a low-voltage high-current AC filament feeding and a high-voltage low-current DC cathode bias, is constructed to serve as the magnetron power source. With a high stability of the power module combined with the usage of water cooling gaskets, over 100 h of plasma processing time was achieved without overheating or causing any damage to the magnetron. Depositions of well-faceted MCD/NCD thin films, with distinct diamond Raman characteristics, were obtained using H2–CH4 discharge with 1–5% CH4. Metal–semiconductor diode structures were fabricated using gold and aluminum as ohmic and rectifying contacts, respectively, and their responses to DC signals revealed a high rectification ratio of up to 106 in the intrinsic MCD/NCD devices. [ABSTRACT FROM AUTHOR]