Enhancing the Efficiency and Stability of Tin-Lead Perovskite Solar Cells via Sodium Hydroxide Dedoping of PEDOT:PSS.

Tin-lead (Sn-Pb) perovskite solar cells (PSCs) have gained interest as candidates for the bottom cell of all-perovskite tandem solar cells due to their broad absorption of the solar spectrum. A notable challenge arises from the prevalent use of the hole transport layer, PEDOT:PSS, known for its inherently high doping level. This high doping level can lead to interfacial recombination, imposing a significant limitation on efficiency. Herein, NaOH is used to dedope PEDOT:PSS, with the aim of enhancing the efficiency of Sn-Pb PSCs. Secondary ion mass spectrometer profiles indicate that sodium ions diffuse into the perovskite layer, improving its crystallinity and enlarging its grains. Comprehensive evaluations, including photoluminescence and nanosecond transient absorption spectroscopy, confirm that dedoping significantly reduces interfacial recombination, resulting in an open-circuit voltage as high as 0.90 V. Additionally, dedoping PEDOT:PSS leads to increased shunt resistance and high fill factor up to 0.81. As a result of these improvements, the power conversion efficiency is enhanced from 19.7% to 22.6%. Utilizing NaOH to dedope PEDOT:PSS also transitions its nature from acidic to basic, enhancing stability and exhibiting less than a 7% power conversion efficiency loss after 1176 h of storage in N2 atmosphere.

Development and Validation of a 3D Resnet Model for Prediction of Lymph Node Metastasis in Head and Neck Cancer Patients.

The accurate diagnosis and staging of lymph node metastasis (LNM) are crucial for determining the optimal treatment strategy for head and neck cancer patients. We aimed to develop a 3D Resnet model and investigate its prediction value in detecting LNM. This study enrolled 156 head and neck cancer patients and analyzed 342 lymph nodes segmented from surgical pathologic reports. The patients' clinical and pathological data related to the primary tumor site and clinical and pathology T and N stages were collected. To predict LNM, we developed a dual-pathway 3D Resnet model incorporating two Resnet models with different depths to extract features from the input data. To assess the model's performance, we compared its predictions with those of radiologists in a test dataset comprising 38 patients. The study found that the dimensions and volume of LNM + were significantly larger than those of LNM-. Specifically, the Y and Z dimensions showed the highest sensitivity of 84.6% and specificity of 72.2%, respectively, in predicting LNM + . The analysis of various variations of the proposed 3D Resnet model demonstrated that Dual-3D-Resnet models with a depth of 34 achieved the highest AUC values of 0.9294. In the validation test of 38 patients and 86 lymph nodes dataset, the 3D Resnet model outperformed both physical examination and radiologists in terms of sensitivity (80.8% compared to 50.0% and 91.7%, respectively), specificity(90.0% compared to 88.5% and 65.4%, respectively), and positive predictive value (77.8% compared to 66.7% and 55.0%, respectively) in detecting individual LNM + . These results suggest that the 3D Resnet model can be valuable for accurately identifying LNM + in head and neck cancer patients. A prospective trial is needed to evaluate further the role of the 3D Resnet model in determining LNM + in head and neck cancer patients and its impact on treatment strategies and patient outcomes.

Biotoxicity of Halide Perovskites in Mice.

Halide perovskites are crystalline semiconductors with exceptional optoelectronic properties, rapidly developing toward large-scale applications. Lead (II) (Pb2+ ) is the core element used to prepare halide perovskites. Pb2+ can displace key 2+ elements, including calcium, zinc and iron, that regulate vital physiological functions. Sn2+ can replace Pb2+ within the perovskite structure and, if accidentally dispersed in the environment, it readily oxidizes to Sn4+ , which is compatible with physiological functions and thus potentially safe. The 3+ salt bismuth (III) (Bi3+ ) is also potentially safe for the same reason and useful to prepare double perovskites. Here, this work studies the biotoxicity of Pb, Sn, and Bi perovskites in mice for the first time. This work analyses histopathology and growth of mice directly exposed to perovskites and investigate the development of their offspring generation. This study provides the screening of organs and key physiological functions targeted by perovskite exposure to design specific studies in mammalians.

A Comparison of Charge Carrier Dynamics in Organic and Perovskite Solar Cells.

The charge carrier dynamics in organic solar cells and organic-inorganic hybrid metal halide perovskite solar cells, two leading technologies in thin-film photovoltaics, are compared. The similarities and differences in charge generation, charge separation, charge transport, charge collection, and charge recombination in these two technologies are discussed, linking these back to the intrinsic material properties of organic and perovskite semiconductors, and how these factors impact on photovoltaic device performance is elucidated. In particular, the impact of exciton binding energy, charge transfer states, bimolecular recombination, charge carrier transport, sub-bandgap tail states, and surface recombination is evaluated, and the lessons learned from transient optical and optoelectronic measurements are discussed. This perspective thus highlights the key factors limiting device performance and rationalizes similarities and differences in design requirements between organic and perovskite solar cells.

Additive-Free, Low-Temperature Crystallization of Stable α-FAPbI3 Perovskite.

Formamidinium lead triiodide (FAPbI3 ) is attractive for photovoltaic devices due to its optimal bandgap at around 1.45 eV and improved thermal stability compared with methylammonium-based perovskites. Crystallization of phase-pure α-FAPbI3 conventionally requires high-temperature thermal annealing at 150 °C whilst the obtained α-FAPbI3 is metastable at room temperature. Here, aerosol-assisted crystallization (AAC) is reported, which converts yellow δ-FAPbI3 into black α-FAPbI3 at only 100 °C using precursor solutions containing only lead iodide and formamidinium iodide with no chemical additives. The obtained α-FAPbI3 exhibits remarkably enhanced stability compared to the 150 °C annealed counterparts, in combination with improvements in film crystallinity and photoluminescence yield. Using X-ray diffraction, X-ray scattering, and density functional theory simulation, it is identified that relaxation of residual tensile strains, achieved through the lower annealing temperature and post-crystallization crystal growth during AAC, is the key factor that facilitates the formation of phase-stable α-FAPbI3 . This overcomes the strain-induced lattice expansion that is known to cause the metastability of α-FAPbI3 . Accordingly, pure FAPbI3 p-i-n solar cells are reported, facilitated by the low-temperature (≤100 °C) AAC processing, which demonstrates increases of both power conversion efficiency and operational stability compared to devices fabricated using 150 °C annealed films.

Phosphorene Nanoribbon-Augmented Optoelectronics for Enhanced Hole Extraction.

Phosphorene nanoribbons (PNRs) have been widely predicted to exhibit a range of superlative functional properties; however, because they have only recently been isolated, these properties are yet to be shown to translate to improved performance in any application. PNRs show particular promise for optoelectronics, given their predicted high exciton binding energies, tunable bandgaps, and ultrahigh hole mobilities. Here, we verify the theorized enhanced hole mobility in both solar cells and space-charge-limited-current devices, demonstrating the potential for PNRs improving hole extraction in universal optoelectronic applications. Specifically, PNRs are demonstrated to act as an effective charge-selective interlayer by enhancing hole extraction from polycrystalline methylammonium lead iodide (MAPbI3) perovskite to the poly(triarylamine) semiconductor. Introducing PNRs at the hole-transport/MAPbI3 interface achieves fill factors above 0.83 and efficiencies exceeding 21% for planar p-i-n (inverted) perovskite solar cells (PSCs). Such efficiencies are typically only reported for single-crystalline MAPbI3-based inverted PSCs. Methylammonium-free PSCs also benefit from a PNR interlayer, verifying applicability to architectures incorporating mixed perovskite absorber layers. Device photoluminescence and transient absorption spectroscopy are used to demonstrate that the presence of the PNRs drives more effective carrier extraction. Isolation of the PNRs in space-charge-limited-current hole-only devices improves both hole mobility and conductivity, demonstrating applicability beyond PSCs. This work provides primary experimental evidence that the predicted superlative functional properties of PNRs indeed translate to improved optoelectronic performance.

Ambient Fabrication of Organic-Inorganic Hybrid Perovskite Solar Cells.

Organic-inorganic hybrid perovskite solar cells (PSCs) have attracted significant attention in recent years due to their high-power conversion efficiency, simple fabrication, and low material cost. However, due to their high sensitivity to moisture and oxygen, high efficiency PSCs are mainly constructed in an inert environment. This has led to significant concerns associated with the long-term stability and manufacturing costs, which are some of the major limitations for the commercialization of this cutting-edge technology. Over the past few years, excellent progress in fabricating PSCs in ambient conditions has been made. These advancements have drawn considerable research interest in the photovoltaic community and shown great promise for the successful commercialization of efficient and stable PSCs. In this review, after providing an overview to the influence of an ambient fabrication environment on perovskite films, recent advances in fabricating efficient and stable PSCs in ambient conditions are discussed. Along with discussing the underlying challenges and limitations, the most appropriate strategies to fabricate efficient PSCs under ambient conditions are summarized along with multiple roadmaps to assist in the future development of this technology.

Correlating the Active Layer Structure and Composition with the Device Performance and Lifetime of Amino-Acid-Modified Perovskite Solar Cells.

Additive engineering is emerging as a powerful strategy to further enhance the performance of perovskite solar cells (PSCs), with the incorporation of bulky cations and amino acid (AA) derivatives being shown as a promising strategy for enhanced device stability. However, the incorporation of such additives typically results in photocurrent losses owing to their saturated carbon backbones, hindering charge transport and collection. Here, we investigate the use of AAs with varying carbon chain lengths as zwitterionic additives to enhance the PSC device stability, in air and nitrogen, under illumination. We, however, discovered that the device stability is insensitive to the chain length as the anticipated photocurrent drops as the chain length increases. Using glycine as an additive results in an improvement in the open circuit voltage from 1.10 to 1.14 V and a resulting power conversion efficiency of 20.2% (20.1% stabilized). Using time-of-flight secondary ion mass spectrometry, we confirm that the AAs reside at the surfaces and interfaces of our perovskite films and propose the mechanisms by which stability is enhanced. We highlight this with glycine as an additive, whereby an 8-fold increase in the device lifetime in ambient air at 1 sun illumination is recorded. Short-circuit photoluminescence quenching of complete devices is reported, which reveals that the loss in photocurrent density observed with longer carbon chain AAs results from the inefficient charge extraction from the perovskite absorber layer. These combined results demonstrate new fundamental understandings about the photophysical processes of additive engineering using AAs and provide a significant step forward in improving the stability of high-performance PSCs.

Chemical vapour deposition (CVD) of nickel oxide using the novel nickel dialkylaminoalkoxide precursor [Ni(dmamp')2] (dmamp' = 2-dimethylamino-2-methyl-1-propanolate).

Nickel oxide (NiO) has good optical transparency and wide band-gap, and due to the particular alignment of valence and conduction band energies with typical current collector materials has been used in solar cells as an efficient hole transport-electron blocking layer, where it is most commonly deposited via sol-gel or directly deposited as nanoparticles. An attractive alternative approach is via vapour deposition. This paper describes the chemical vapour deposition of p-type nickel oxide (NiO) thin films using the new nickel CVD precursor [Ni(dmamp')2], which unlike previous examples in literature is synthesised using the readily commercially available dialkylaminoalkoxide ligand dmamp' (2-dimethylamino-2-methyl-1-propanolate). The use of vapour deposited NiO as a blocking layer in a solar-cell device is presented, including benchmarking of performance and potential routes to improving performance to viable levels.

ZnO-PCBM bilayers as electron transport layers in low-temperature processed perovskite solar cells.

We investigate an electron transport bilayer fabricated at <110 °C to form all low-temperature processed, thermally stable, efficient perovskite solar cells with negligible hysteresis. The components of the bilayer create a symbiosis that results in improved devices compared with either of the components being used in isolation. A sol-gel derived ZnO layer facilitates improved energy level alignment and enhanced charge carrier extraction and a [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) layer to reduce hysteresis and enhance perovskite thermal stability. The creation of a bilayer structure allows materials that are inherently unsuitable to be in contact with the perovskite active layer to be used in efficient devices through simple surface modification strategies.

Valproic acid mediates the synaptic excitatory/inhibitory balance through astrocytes--a preliminary study.

Valproic acid (VPA) is one of the most widely used anticonvulsant and mood-stabilizing agents for the treatment of epilepsy and bipolar disorder. However, the underlying therapeutic mechanisms of the treatment of each disease remain unclear. Recently, the anti-epileptic effect of VPA has been found to lead to modulation of the synaptic excitatory/inhibitory balance. In addition, the therapeutic action of VPA has been linked to its effect on astrocytes by regulating gene expression at the molecular level, perhaps through an epigenetic mechanism as a histone deacetylase (HDAC) inhibitor. To provide insight into the mechanisms underlying the actions of VPA, this study investigated whether the synaptic excitatory/inhibitory (E/I) balance could be mediated by VPA through astrocytes. First, using the primary rat neuronal, astroglial, and neuro-glial mixed culture systems, we demonstrated that VPA treatment could regulate the mRNA levels of two post-synaptic cell adhesion molecules(neuroligin-1 and neuregulin-1) and two extracellular matrices (neuronal pentraxin-1and thrombospondin-3) in primary rat astrocyte cultures in a time- and concentration-dependent manner. Moreover, the up-regulation effect of VPA was noted in astrocytes, but not in neurons. In addition, these regulatory effects could be mimicked by sodium butyrate, a HDAC inhibitor, but not by lithium or two other glycogen synthase kinase-3 beta inhibitors. With the known role of these four proteins in regulating the synaptic E/I balance, we further demonstrated that VPA increased excitatory post-synaptic protein (postsynaptic density 95) and inhibitory post-synaptic protein (Gephyrin) in cortical neuro-glial mixed cultures. Our results suggested that VPA might affect the synaptic excitatory/inhibitory balance through its effect on astrocytes. This work provides the basis for future evaluation of the role of astroglial cell adhesion molecules and the extracellular matrix on the control of excitatory and inhibitory synapse formation.