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Semiconductor nanomaterials with controlled morphologies and architectures are of critical importance for high-performance optoelectronic devices. However, the fabrication of such nanomaterials on polymer-based flexible electrodes is particularly challenging due to degradation of the flexible electrodes at a high temperature. Here we report the fabrication of nickel oxide nanopillar arrays (NiO x NaPAs) on a flexible electrode by vapor deposition, which enables highly efficient perovskite solar cells (PSCs). The NiO x NaPAs exhibit an enhanced light transmittance for light harvesting, prohibit exciton recombination, promote irradiation-generated hole transport and collection, and facilitate the formation of large perovskite grains. These advantageous features result in a high efficiency of 20% and 17% for the rigid and flexible PSCs, respectively. Additionally, the NaPAs show no cracking after 500 times of bending, consistent with the mechanic simulation results. This robust fabrication opens a new opportunity for the fabrication of a large area of high-performance flexible optoelectronic devices.

Nano-size Y-Ti-oxides are largely responsible for the extraordinary mechanical properties and irradiation tolerance of nano-structured ferritic alloys (NFAs). Here we report a theoretical study to assess the characters and possible roles of the ferrite/oxide interface in managing neutron transmutation product helium in NFAs. Using one observed cube-on-cube orientation relationship, various candidate structures of the ferrite/Y2Ti2O7 interfaces were constructed and the associated energies were carefully evaluated. The interface phase diagram is obtained by expressing the energy as a function of temperature and internal oxygen activity (expressed in terms of oxygen partial pressure). The oxide interfaces are predicted to be Y/Ti-rich at thermodynamic equilibrium for the wide temperature range of interest. Vacancy formation energies are lower and helium segregates to the interfaces, in preference to the iron matrix and grain boundaries. Combined with our previous results on bulk-phase Y2Ti2O7, the profound implications of nano-oxides to helium management in NFAs are discussed.

devices, flexible substrates play a key role to fabricate high-performance electronics. In the past decade, various flexible substrates have been greatly developed. For instance, Chongwu and co-workers fabricated silver nanowire films on flexible polyethylene terephthalate (PET) substrates with good mechanical flexibility and demonstrated the application in a touch panel. [7] Johansson and co-workers reported a polyethylene naphthalate (PEN) substrate coated by Ag nanowire network for an extremely lightweight and ultraflexible colloidal quantum dots solar cell. [8] Jeong and co-workers fabricated copper conductors on polyimide and polyethersulfone substrates, exhibiting the potential accessibility for flexible electronics. [9] The abovementioned flexible substrates exhibit excellent stretchable ability and high-flexible performance. Because of their excellent mechanical and chemical stability, it takes extremely long time for them to degrade or decompose in the nature, leading to environmental pollution. Therefore, more and more attention is paid to looking for flexi ble, biocompatible, and environmentally friendly biomass substrates for wearable devices. [6,[10][11][12][13] Flexible biomass substrates based on nanofibrillated cellulose have been explored and are expected to be used in wearable electronics due to their excellent mechanical properties, renewability, and raw material abundance. Ma and co-workers successfully fabricated gallium arsenide microwave devices on flexible wood-derived cellulose nanofibril paper. [14] Ju and co-workers reported flexible, transparent phototransistors on biodegradable wood-derived cellulose nanofibrillated fiber substrates toward environment friendly electronics. [15] Hu and co-workers fabricated flexible organic field-effect transistors on tailorable softwood-derived nanopapers. [16] These successful studies suggest the feasibility to fabricate environment friendly cellulose-based substrates for flexible electronics, and further accelerate development of the flexible wearable devices.Currently flexible perovskite solar cells (PSCs) have gained wide attention by their excellent performance and potential application in wearable energy devices. [13,[17][18][19] As is well known, high performance flexible perovskite devices are still based on nonbiocompatible and nondegradable plastic substrates such as PET, PEN, and polydimethylsiloxane. Yu and co-workers first reported flexible perovskite solar cells fabricated on Wearable devices are mainly based on plastic substrates, such as polyethylene terephthalate and polyethylene naphthalate, which causes environmental pollution after use due to the long decomposition periods. This work reports on the fabrication of a biodegradable and biocompatible transparent conductive electrode derived from bamboo for flexible perovskite solar cells. The conductive bioelectrode exhibits extremely flexible and light-weight properties. After bending 3000 times at a 4 mm curvature radius or even undergoing a crumpling test, it still shows excellent e...

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For the fabrication of deformable electronic devices, electrodes that are robust against repeated bending, twisting, stretching, folding, reversible plasticizing, and that maintain electrical conductivity, and so on, are required. Malleable and pliable silk‐derived electrodes are fabricated to enable the shape deformation of perovskite solar cells. Moisture‐driven silk‐derived electrodes show reversible plasticization with malleability and pliability, realizing diverse deformation from simple operations (including bending, folding, stretching, etc.) to complicated structures (including flower, bowknot, and paper crane). It is worth noting that the silk‐derived electrodes maintain electrical conductivity (15.8 Ω sq−1) compared to their initial value (15 Ω sq−1) even after suffering from reversible mechanical plasticization of complicated structures. Deformable perovskite solar cells are fabricated with the silk‐derived electrodes and achieve a power conversion efficiency of 10.40%. The devices maintain 92% of the initial efficiency after 1000 bends at a curvature radius of 2.5 mm. The power does not decline at 50% strain and keeps more than 60% of the initial value after stretching for 50 cycles. Malleability and pliability of silk‐derived electrodes benefit the realization of stretchable perovskite solar cells and deformable electronic devices.

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