In this contribution, inspired by the excellent resource management and material transport function of leaf veins, the electrical transport function of metallized leaf veins is mimicked from the material transport function of the vein networks. By electroless copper plating on real leaf vein networks with copper thickness of only several hundred nanometre up to several micrometre, certain leaf veins can be converted to transparent conductive electrodes with an ultralow sheet resistance 100 times lower than that of state-of-the-art indium tin oxide thin films, combined with a broadband optical transmission of above 80% in the UV–VIS–IR range. Additionally, the resource efficiency of the vein-like electrode is characterized by the small amount of material needed to build up the networks and the low copper consumption during metallization. In particular, the high current density transport capability of the electrode of > 6000 A cm⁻² was demonstrated. These superior properties of the vein-like structures inspire the design of high-performance transparent conductive electrodes without using critical materials and may significantly reduce the Ag consumption down to < 10% of the current level for mass production of solar cells and will contribute greatly to the electrode for high power density concentrator solar cells, high power density Li-ion batteries, and supercapacitors.

We describe the preparation and properties of bilayers of graphene‐ and multi‐walled carbon nanotubes (MWCNTs) as an alternative to conventionally used platinum‐based counter electrode for dye‐sensitized solar cells (DSSC). The counter electrodes were prepared by a simple and easy‐to‐implement double self‐assembly process. The preparation allows for controlling the surface roughness of electrode in a layer‐by‐layer deposition. Annealing under N₂ atmosphere improves the electrode's conductivity and the catalytic activity of graphene and MWCNTs to reduce the I₃⁻ species within the electrolyte of the DSSC. The performance of different counter‐electrodes is compared for ZnO photoanode‐based DSSCs. Bilayer electrodes show higher power conversion efficiencies than monolayer graphene electrodes or monolayer MWCNTs electrodes. The bilayer graphene (bottom)/MWCNTs (top) counter electrode‐based DSSC exhibits a maximum power conversion efficiency of 4.1 % exceeding the efficiency of a reference DSSC with a thin film platinum counter electrode (efficiency of 3.4 %). In addition, the double self‐assembled counter electrodes are mechanically stable, which enables their recycling for DSSCs fabrication without significant loss of the solar cell performance.

We present a concept for a core-shell silicon nanowire thin-film solar cell showing strong light trapping. Nanowires are wet chemically etched into a several micrometer-thick laser-crystallized silicon thin film on glass. The nanowires are equipped with an a-Si heteroemitter deposited as a shell around the nanowires by plasma-enhanced chemical vapor deposition to achieve a radial p-n heterojunction. The space between the nanowires is filled with ZnO:Al, acting as a transparent contact. Our core-shell nanowire solar cells reached an efficiency of 8.8%. The main emphasis of this study is on the optical properties of the nanowire solar cell system.