Large-scale arrays of highly oriented hexagonal ZnO nanorods and nanotubes were fabricated on arbitrary ZnO-film-coated substrates using a low-temperature chemical-liquid-phase deposition method. The obtained nanoproducts were characterized, and the growth mechanism is proposed.

Using a femtosecond resolved up‐conversion technique, the ultrafast carrier dynamics in fluorescent carbon nanodots are investigated in order to shed light on the mysterious origins of their fluorescence. These experiments reveal that the fluorescence of carbon nanodots consists of two spectral overlapped bands that can be ascribed to the intrinsic and extrinsic fluorescence. The intrinsic band exhibits a small bandwidth of 175 meV at 459 nm, and it is attributed to the sp2 nano domains. The extrinsic band originates from the surface states with a much broader bandwidth of 450 meV. The relaxation with time constants of a few picoseconds, tens of picoseconds, and a few nanoseconds are attributed to optical phonon scattering, acoustic phonon scattering, and carrier (e–h pair) recombination, respectively. A fast trapping is observed from the nano domains into the surface states with a time constant of 400 fs. The excitation wavelength‐dependent fluorescence can arise from the abundant carboxyl functional groups on the surface.

Minimizing energy loss is of critical importance in the pursuit of attaining high-performance organic solar cells. Interestingly, reorganization energy plays a crucial role in photoelectric conversion processes. However, the understanding of the relationship between reorganization energy and energy losses has rarely been studied. Here, two acceptors, Qx-1 and Qx-2, were developed. The reorganization energies of these two acceptors during photoelectric conversion processes are substantially smaller than the conventional Y6 acceptor, which is beneficial for improving the exciton lifetime and diffusion length, promoting charge transport, and reducing the energy loss originating from exciton dissociation and non-radiative recombination. So, a high efficiency of 18.2% with high open circuit voltage above 0.93 V in the PM6:Qx-2 blend, accompanies a significantly reduced energy loss of 0.48 eV. This work underlines the importance of the reorganization energy in achieving small energy losses and paves a way to obtain high-performance organic solar cells.

Volatile solid additives (SADs) are considered as a simple yet effective approach to tune the film morphology for high-performance organic solar cells (OSCs). However, the structural effects of the SADs on the photovoltaic performance are still elusive. Herein, two volatilizable SADs were designed and synthesized. One is SAD1 with twisted conformation, while the other one is planar SAD2 with the S···O noncovalent intramolecular interactions (NIIs). The theoretical and experimental results revealed that the planar SAD2 with smaller space occupation can more easily insert between the Y6 molecules, which is beneficial to form a tighter intermolecular packing mode of Y6 after thermal treatment. As a result, the SAD2-treated OSCs exhibited less recombination loss, more balanced charge mobility, higher hole transfer rate, and more favorable morphology, resulting in a record power conversion efficiency (PCE) of 18.85% (certified PCE: 18.7%) for single-junction binary OSCs. The universality of this study shed light on understanding the conformation effects of SADs on photovoltaic performances of OSCs.

Mixed tin (Sn)-lead (Pb) perovskite is considered the most promising low-bandgap photovoltaic material for both pursuing the theoretical limiting efficiency of single-junction solar cells and breaking the Shockley-Queisser limitation by constructing tandem solar cells. However, their power conversion efficiencies (PCEs) are still lagging behind those of medium-bandgap perovskite solar cells (pero-SCs) due to their serious energy loss (E loss ). In this work, we used an ultra-thin bulkheterojunction (BHJ) organic semiconductor (PBDB-T:ITIC) layer as an intermediary between the hole transporting layer and Sn-Pb-based low-bandgap perovskite film to minimize E loss . It was found that this BHJ PBDB-T:ITIC intermediary simultaneously provided a cascading energy alignment in the device, facilitated high-quality Sn-Pb perovskite film growth, and passivated the antisite defects of the perovskite surface. In this simple way, the E loss of pero-SCs based on (FASnI 3 ) 0.6 (MAPbI 3 ) 0.4 (bandgap ≈ 1.25 eV) was dramatically reduced below 0.4 eV, leading to a high open-circuit voltage (V oc ) of 0.86 V. As a result, the best pero-SC showed a significantly improved PCE of 18.03% with negligible J-V hysteresis and high stability. To the best of our knowledge, the PCE of 18.03% and V oc of 0.86 V are the highest values among the low-bandgap pero-SCs to date.

Interchain interaction, i.e., pi-pi stacking, can benefit the carrier transport in conjugated regio-regular poly(3-hexylthiophene) (P3HT) thin films. However, the existence of the insulating side hexyl chains in the surface region may be detrimental to the charge transfer between the polymer backbone and overlayer molecules. The control of the molecular orientation in the surface region is expected to alter the distribution of the pi electron density at the surface to solve such problems, which can be achieved by controlling the solvent removal rate during solidification. The evidence that the pi-electron density distribution at the outermost surface can be controlled is demonstrated by the investigation using the powerful combination of near edge X-ray absorption fine structure spectroscopy, ultraviolet photoelectron spectroscopy, and the most surface-sensitive technique: Penning ionization electron spectroscopy. From the spectroscopic studies, it can be deduced that the slower removal rate of the solvent makes the polymer chains even at the surface have sufficient time to adopt a more nearly equilibrium structure with edge-on conformation. Thus, the side hexyl chains extend outside the surface, which buries the pi-electron density contributed from the polymer backbone. Contrarily, the quench of obtaining a thermo-equilibrium structure in the surface region due to the faster removal of the solvent residual can lead to the surface chain conformation without persisting to the strong bulk orientation preference. Therefore, the face-on conformation of the polymer chain at the surface of thin films coated with high spin coating speed facilitate the electron density of the polymer backbone exposed outside the surface. Finally, thickness dependence of the surface electronic structure of P3HT thin films is also discussed.

A PCDTBT:PC71BM solar cell adopted by a ternary strategy with PDTSTPD achieves an overall PCE of 20.8% under indoor illumination.

The direct electrodeposition of crystalline germanium (Ge) nanowire film electrodes from an aqueous solution of dissolved GeO(2) using discrete 'flux' nanoparticles capable of dissolving Ge(s) has been demonstrated. Electrodeposition of Ge at inert electrode substrates decorated with small (<100 nm), discrete indium (In) nanoparticles resulted in crystalline Ge nanowire films with definable nanowire diameters and densities without the need for a physical or chemical template. The Ge nanowires exhibited strong polycrystalline character as-deposited, with approximate crystallite dimensions of 20 nm and a mixed orientation of the crystallites along the length of the nanowire. Energy dispersive spectroscopic elemental mapping of individual Ge nanowires showed that the In nanoparticles remained at the base of each nanowire, indicating good electrical communication between the Ge nanowire and the underlying conductive support. As-deposited Ge nanowire films prepared on Cu supports were used without further processing as Li(+) battery anodes. Cycling studies performed at 1 C (1624 mA g(-1)) indicated the native Ge nanowire films supported stable discharge capacities at the level of 973 mA h g(-1), higher than analogous Ge nanowire film electrodes prepared through an energy-intensive vapor-liquid-solid nanowire growth process. The cumulative data show that ec-LLS is a viable method for directly preparing a functional, high-activity nanomaterials-based device component. The work presented here is a step toward the realization of simple processes that make fully functional energy conversion/storage technologies based on crystalline inorganic semiconductors entirely through benchtop, aqueous chemistry and electrochemistry without time- or energy-intensive process steps.