The role of residual lead iodide on the photophysical properties of methylammonium lead iodide is still unclear and contradictory views exist about its impact. Herein, it is reported that there is a critical amount of residual lead iodide, which is beneficial for the solar cell performance. Transient absorption spectroscopy is used to investigate the charge carrier recombination dynamics in perovskite solar cells and to address the role of different amounts of residual lead iodide. The amount of lead iodide is varied through the perovskite thin film preparation protocol upon a modified two-step fabrication process. Slower carrier dynamics are observed at the perovskite/titanium dioxide interface in the presence of residual lead iodide when exciting the perovskite at the perovskite/titanium interface, which correlates with improved solar cell device performance. Excitation from the perovskite side indicates that the effect of residual lead iodide is primarily at the titanium dioxide interface. Increasing the lead iodide content does not further alter the carrier recombination; on the contrary, it results in lower device performance. This study confirms that the presence of lead iodide can have a beneficial effect, as it reduces charge carrier recombination at the perovskite/titanium dioxide interface.

Optoelectronic devices typically require low-resistance Ohmic contacts between the optical active layers and metal electrodes. Failure to make such a contact often results in a Schottky barrier which inhibits charge extraction and, in turn, reduces device performance. Here, we introduce a universal solution processable metal-oxide/organic interfacial bilayer which forms a near-perfect ohmic contact between both organic and inorganic semiconductors and metals. This bilayer comprises a Nb-doped TiO2 metal oxide with enhanced electron mobility and reduced trap density compared to pristine TiO2, in combination with a metal-chelating organic molecule to make an intimate electrical contact with silver metallic electrodes. Using this universal interfacial bilayer, we demonstrate substantial efficiency improvements in organic solar cells (from 9.3% to 12.6% PCE), light emitting diodes (from 0.6 to 2.2 Cd W-1) and transistors (from 19.7 to 13.9 V threshold voltage). In particular, a boost in efficiency for perovskite solar cells (from 18.7% up to 20.7% PCE) with up to 83% fill factor is achieved with no-operational lifetime loss for at least 1000 hours under continuous, full-spectrum illumination.

This paper investigated the use of semipolar InGaN/GaN multiple quantum well based micro-photodetectors (μPDs) as the optical receiver for visible light communication (VLC). The fabricated semipolar μPDs exhibited a low dark current of 1.6 pA at −10 V, a responsivity of 0.191 A W−1, and a −3 dB modulation bandwidth of 347 MHz. A high data rate of up to 1.55 Gbit s−1 was achievable by utilizing the extended bandwidth of more than −10 dB, and based on a straight-forward non-return-to-zero on–off keying modulation scheme. This development demonstrated the feasibility of wavelength-selective detection scheme using semipolar μPD for high-data-capacity VLC systems.

Lipid Droplets (LDs) are emerging as crucial players in colon cancer development and maintenance. Their expression has been associated with high tumorigenicity in Cancer Stem Cells (CSCs), so that they have been proposed as a new functional marker in Colorectal Cancer Stem Cells (CR-CSCs). They are also indirectly involved in the modulation of the tumor microenvironment through the production of pro-inflammatory molecules. There is growing evidence that a possible connection between metabolic alterations and malignant transformation exists, although the effects of nutrients, primarily glucose, on the CSC behavior are still mostly unexplored. Glucose is an essential fuel for cancer cells, and the connections with LDs in the healthy and CSC populations merit to be more deeply investigated. Here, we showed that a high glucose concentration activated the PI3K/AKT pathway and increased the expression of CD133 and CD44v6 CSC markers. Additionally, glucose was responsible for the increased amount of Reactive Oxygen Species (ROS) and LDs in both healthy and CR-CSC samples. We also investigated the gene modulations following the HG treatment and found out that the healthy cell gene profile was the most affected. Lastly, Atorvastatin, a lipid-lowering drug, induced the highest mortality on CR-CSCs without affecting the healthy counterpart.

An antiferromagnetic NiO spiral wall in Fe/NiO/Co0.5Ni0.5O/vicinal Ag(001) was created by rotating Fe magnetization and investigated using x-ray magnetic linear dichroism (XMLD). Different from the Mauri's 180° spiral wall, we find that the NiO spiral wall always switches its chirality at ~ 90° rotation of the Fe magnetization, and unwinds the spiral wall back to a single domain with a further rotation of the Fe magnetization from 90° to 180°. The effect of this chirality switching on the magnetic anisotropy was studied using rotational magneto-optic Kerr effect (ROTMOKE) on Py/NiO/Co0.5Ni0.5O/vicinal Ag(001). We find that the original Mauri's model has to be corrected by an energy folding due to the chirality switching, which consequently converts the exchange bias from the Mauri's 180° spiral wall into a uniaxial anisotropy and a negative fourfold anisotropy.

The efficiency of state-of-the-art perovskite solar cells is limited by carrier recombination at defects and interfaces. Thus, understanding these losses and how to reduce them is the way forward toward the Shockley-Queisser limit. Here, we demonstrate that ultrafast transient absorption spectroscopy can directly probe hole extraction and recombination dynamics at perovskite/hole transport layer (HTL) interfaces. To illustrate this, we employed PDPP-3T as HTL because its ground-state absorption is at lower energy than the perovskite's photobleach, enabling direct monitoring of interfacial hole extraction and recombination. Moreover, by fitting the carrier dynamics using a diffusion model, we determined the carrier mobility. Afterwards, by varying the perovskite thickness, we distinguished between carrier diffusion and carrier extraction at the interface. Lastly, we prepared device-like structures, TiO2/perovskite/PDPP-3T stacks, and observed reduced carrier recombination in the perovskite. From PDPP-3T carrier dynamics, we deduced that hole extraction is one order faster than recombination of holes at the interface.

Molar fractions are used in applied diffusion kinetics for incorporating thermodynamic and kinetic databases. Molar quantities (molar concentration and molar flux) and reduced molar quantities (molar fraction and reduced molar flux) usually are regarded to be equivalent; i.e., molar quantities are replaced with their reduced forms. However, as the fluxes are related to material properties, the diffusion equations expressed in molar fractions are not consistent with the normalization condition of molar fractions. We develop diffusion kinetics consistent with this condition. Our method is applicable to diffusion with total reduced flux, such as diffusion in an external field or flow field. As two case studies, the developed method is used to investigate ionic diffusion in an electrolyte solution and ionic demixing in a semiconductor oxide.

With the advent of flexible and wearable electronics and sensors, there is an urgent need to develop energy-harvesting solutions that are compatible with such wearables. However, many of the proposed energy-harvesting solutions lack the necessary mechanical properties, which make them susceptible to damage by repetitive and continuous mechanical stresses, leading to serious degradation in device performance. Developing new energy materials that possess high deformability and self-healability is essential to realize self-powered devices. Herein, a thermoelectric ternary composite is demonstrated that possesses both self-healing and stretchable properties produced via 3D-printing method. The ternary composite films provide stable thermoelectric performance during viscoelastic deformation, up to 35% tensile strain. Importantly, after being completely severed by cutting, the composite films autonomously recover their thermoelectric properties with a rapid response time of around one second. Using this self-healable and solution-processable composite, 3D-printed thermoelectric generators are fabricated, which retain above 85% of their initial power output, even after repetitive cutting and self-healing. This approach represents a significant step in achieving damage-free and truly wearable 3D-printed organic thermoelectrics.

Giant planar Hall effect arising from chiral anomaly, which is related to the Berry curvature, has been predicted and realized in nonmagnetic Dirac/Weyl semimetals. Here, we report the observation of the anisotropic planar Hall effect in type-II Weyl semimetal WTe2. Interestingly, we observed chiral-anomaly-induced sinusoidal angular dependent PHE when the electric field is parallel to the tilting direction of Weyl cone, i.e. b-axis of WTe2. The PHE amplitude is linearly dependent on the magnetic fields and decreases gradually as the temperature increases across the topological phase transition temperature. Our observations clearly revealed the footprints on transport from the chiral anomaly feature in type-II Weyl semimetals.