Large-Scale Preparation of Low-Cost Nonfullerene Acceptors for Stable and Efficient Organic Solar Cells

Despite the development of nonfullerene acceptors (NFAs) that have made a breakthrough in the photovoltaic performance, large-scale preparation of NFAs that is prerequisite for commercial application has never been explored. Herein, we designed two dodecacyclic all-fused-ring electron acceptors, F11 and F13, and develop a whole set of synthetic procedures, achieving unprecedented scalable preparation of NFAs in the lab at a 10-g scale notably within one day. The single-crystal structures of F11 reveals the 3D network packing. F11 and F13 display the lowest costs among reported NFAs, even comparable with the classical donor material, P3HT. By matching a medium-bandgap polymer donor, F13 delivers power conversion efficiencies of over 13%, which is an efficiency record for non-INCN acceptors. Benefiting from the intrinsically high stability, OSCs based on F11 and F13 show device stability superior to the typical ITIC- and Y6-based OSCs as evidenced by the tiny burn-in losses. The current work presents a first example for large-scale preparation of low-cost NFAs with good efficiency and high device stability, which is significant for OSC commercialization in near future.

Design of a system for controlling a levitating sphere in superfluid 3He at extremely low temperatures

We present a new mechanical probe to study the properties of superfluid 3He at microkelvin temperatures down to 100 μK. The setup consists of a set of coils for levitating a superconducting sphere and controlling its motion in a wide variety of regimes. In particular, the realisation of motion of a levitating body at a uniform velocity presents both an experimental challenge and a promising direction into the study of the edge states in topological superfluid 3He-B. We include the theoretical study of the device stability and simulations to illustrate the capabilities of the control system.

Photovoltaics: towards ultimate performances

Photovoltaic conversion has made impressive progress since its discovery, but as will be discussed here, much can still be done. It is of interest to investigate what are the intrinsic limits of the technology. We call here ultimate performance those that could be limited only by intrinsic properties of the devices. This point will be discussed along three lines: ultimate limits for energy conversion, ultimate limits for material usage and ultimate limits for device stability.

Stable epidermal electronic device with strain isolation induced by in situ Joule heating

Epidermal electronics play increasingly important roles in human-machine interfaces. However, their efficient fabrication while maintaining device stability and reliability remains an unresolved challenge. Here, a facile in situ Joule heating method is proposed for fabricating stable epidermal electronics on a polyvinyl alcohol (PVA) substrate. Benefitting from the precise control of heating locations, the crystallization and enhanced rigidity of PVA are restricted to desired areas, leading to strain isolation of the active regions. As a result, the electronic device can be conformably attached to skin while showing negligible degradation in device performance during deformation. Based on this method, a flexible surface electromyography (sEMG) sensor with outstanding stability and highly comfortable wearability is demonstrated, showing high accuracy (91.83%) for human hand gesture recognition. These results imply that the fabrication method proposed in this research is a facile and reliable approach for the fabrication of epidermal electronics.

Design of a system for controlling a levitating sphere in superfluid 3He at extremely low temperatures

We present a new mechanical probe to study the properties of superfluid 3 He at microkelvin temperatures down to 100µK. The setup consists of a set of coils for levitating a superconducting sphere and controlling its motion in a wide variety of regimes. In particular, the realisation of motion of a levitating body at a uniform velocity presents both an experimental challenge and a promising direction into the study of the edge states in topological superfluid 3 He-B. We include the theoretical study of the device stability and simulations to illustrate the capabilities of the control system.

Revealing molecular conformation–induced stress at embedded interfaces of organic optoelectronic devices by sum frequency generation spectroscopy

Interface stresses are pervasive and critical in conventional optoelectronic devices and generally lead to many failures and reliability problems. However, detection of the interface stress embedded in organic optoelectronic devices is a long-standing problem, which causes the unknown relationship between interface stress and organic device stability (one key and unsettled issue for practical applications). In this study, a kind of previously unknown molecular conformation–induced stress is revealed at the organic embedded interface through sum frequency generation (SFG) spectroscopy technique. This stress can be greater than 10 kcal/mol per nm2 and is sufficient to induce molecular disorder in the organic semiconductor layer (with energy below 8 kcal/mol per nm2), finally causing instability of the organic transistor. This study not only reveals interface stress in organic devices but also correlates instability of organic devices with the interface stress for the first time, offering an effective solution for improving device stability.