Silicon nanowires (SiNWs) with desirable axial crystallographic orientations can be readily prepared by a novel chemical‐etching technique (see SEM image). The as‐synthesized SiNW arrays significantly suppress reflection over the visible‐light spectral range and are therefore promising candidates for antireflection coatings of photovoltaic cells despite exhibiting a lower efficiency than non‐nanowire‐based devices at this stage of development.

A novel strategy for preparing large‐area, oriented silicon nanowire (SiNW) arrays on silicon substrates at near room temperature by localized chemical etching is presented. The strategy is based on metal‐induced (either by Ag or Au) excessive local oxidation and dissolution of a silicon substrate in an aqueous fluoride solution. The density and size of the as‐prepared SiNWs depend on the distribution of the patterned metal particles on the silicon surface. High‐density metal particles facilitate the formation of silicon nanowires. Well‐separated, straight nanoholes are dug along the Si block when metal particles are well dispersed with a large space between them. The etching technique is weakly dependent on the orientation and doping type of the silicon wafer. Therefore, SiNWs with desired axial crystallographic orientations and doping characteristics are readily obtained. Detailed scanning electron microscopy observations reveal the formation process of the silicon nanowires, and a reasonable mechanism is proposed on the basis of the electrochemistry of silicon and the experimental results.

Neatly scratching the surface: A facile etching technique assisted by a silver‐nanoparticle network to produce large‐area 1D silicon nanostructure arrays with desired orientation and doping characteristics is demonstrated (see picture). A mechanism for the highly selective etching is proposed on the basis of experimental evidence.

Large-area slantingly-aligned silicon nanowire arrays (SA-SiNW arrays) on Si(111) substrate have been fabricated by wet chemical etching with dry metal deposition method and employed in the fabrication of solar cells for the first time. The formation of SA-SiNW arrays possibly results from the anisotropic etching of silicon by silver catalysts. Superior to the previous cells fabricated with vertically-aligned silicon nanowire arrays (VA-SiNW arrays), the SA-SiNW array solar cells exhibit a highest power conversion efficiency of 11.37%. The improved device performance is attributed to the integration of the excellent anti-reflection property of the arrays and the better electrical contact of the cell as a result of the special slantingly-aligned structure. The high surface recombination velocity of minority carriers in SiNW arrays is still the main limitation on cell performance.

We report a metal-insulator-semiconductor heterojunction solar cell by depositing a carbon nanotube film onto silicon substrate, followed by acid oxidation of the Si surface to form a thin oxide layer at the junction interface. The nanotube-oxide-Si solar cells with polymer encapsulation show stable efficiencies of above 10%, owing to enhanced photon absorption, inhibited charge recombination, and reduced internal resistance. Parallel and series connections without sacrificing cell efficiencies were demonstrated.

Feine Kratzer auf der Oberfläche: Eine einfache Ätztechnik, die von einem Ag‐Nanopartikelnetzwerk unterstützt wird und großflächige 1D‐Anordnungen von Siliciumnanostrukturen mit der gewünschten Orientierung und Dotierungscharakteristik liefert, wird vorgestellt (siehe Bild). Aus den experimentellen Befunden wird ein Mechanismus für das hoch selektive Ätzen abgeleitet.

Defect state passivation and conductivity of materials are always in opposition; thus, it is unlikely for one material to possess both excellent carrier transport and defect state passivation simultaneously. As a result, the use of partial passivation and local contact strategies are required for silicon solar cells, which leads to fabrication processes with technical complexities. Thus, one material that possesses both a good passivation and conductivity is highly desirable in silicon photovoltaic (PV) cells. In this work, a passivation‐conductivity phase‐like diagram is presented and a conductive‐passivating‐carrier‐selective contact is achieved using PEDOT:Nafion composite thin films. A power conversion efficiency of 18.8% is reported for an industrial multicrystalline silicon solar cell with a back PEDOT:Nafion contact, demonstrating a solution‐processed organic passivating contact concept. This concept has the potential advantages of omitting the use of conventional dielectric passivation materials deposited by costly high‐vacuum equipment, energy‐intensive high‐temperature processes, and complex laser opening steps. This work also contributes an effective back‐surface field scheme and a new hole‐selective contact for p‐type and n‐type silicon solar cells, respectively, both for research purposes and as a low‐cost surface engineering strategy for future Si‐based PV technologies.

To attain a deep understanding of ferroelectric and piezoelectric characteristics of K0.5Na0.5NbO3 as a promising lead-free compound, the ferroelectric and piezoelectric responses of its epitaxially grown films with three primary orientations of [001], [110], and [111] were investigated with an emphasis on the influence of crystallographic orientation. The films were prepared by sol-gel processing using Nb-doped SrTiO3 single-crystalline substrates with various cutting directions. A peak remnant polarization value (Pr) of 17.3 μC/cm2 was obtained along the [110] direction due to the coincidence between the spontaneous polarization and the film orientation, which is significantly higher than 10.5 μC/cm2 in [111]-oriented and 10.1 μC/cm2 in [001]-oriented ones. However, a better piezoelectric response was achieved in the [001]-oriented films with an average local effective piezoelectric coefficient (d33) of 50.5 pm/V, as compared with 45.1 pm/V and 39.7 pm/V in [110]- and [111]-oriented films, respectively.