Recyclable Monolithic Vitrimer Foam for High-Efficiency Solar-Driven Interfacial Evaporation

With the exponentially rapid development of solar-driven interfacial evaporation, evaporators with both high evaporation efficiency and recyclability are highly desirable to alleviate resource waste and environmental problems but remain challenging. Here, a monolithic evaporator was developed based on a dynamic disulfide vitrimer (a covalently cross-linked polymer network with associative exchangeable covalent bonds). Two types of solar absorbers, carbon nanotubes and oligoanilines, were simultaneously introduced to enhance the optical absorption. A high evaporation efficiency of 89.2% was achieved at 1 sun (1 kW m–2). When the evaporator was applied to solar desalination, it shows self-cleaning performance with long-term stability. Drinkable water with low ion concentrations satisfying the drinkable water levels of the World Health Organization and a high output (8.66 kg m–2, 8 h per day) was obtained, revealing great potential for practical seawater desalination. Moreover, a high-performance film material was obtained from the used evaporator via simple hot-pressing, indicating excellent fully closed-loop recyclability of the evaporator. This work provides a promising platform for high-efficiency and recyclable solar-driven interfacial evaporators

Harnessing the Day–Night Rhythm of Humidity and Sunlight into Mechanical Work Using Recyclable and Reprogrammable Soft Actuators

Toward a sustainable society, soft actuators driven by environmentally friendly energy from nature are of great social and economic significance. Meanwhile, recyclability, repeated reconfiguration for other use, and complex three-dimensional (3D) geometries are also essential for mitigating the energy crisis and practical application demands. Here, we integrate all of the above features in one actuator using vitrimers with exchangeable disulfide links. By reconfiguration, welding, patterning, and kirigami techniques, complex 3D actuators can be easily fabricated, which can be repeatedly reconfigured for other applications to save cost in new material preparation. These actuators operate synergistically with the day–night rhythm of humidity and sunlight without the need of extra energy input

Ultrathin Flexible Transparent Composite Electrode via Semi-embedding Silver Nanowires in a Colorless Polyimide for High-Performance Ultraflexible Organic Solar Cells

Ultraflexible organic solar cells (OSCs) with both high power conversion efficiency (PCE) and good mechanical robustness are still challenging, in which flexible transparent composite electrodes (FTCEs, substrate-cum-electrodes) play critical roles. Here, an ultrathin FTCE (∼9 μm) via semi-embedding a silver nanowire electrode in a colorless polyimide (CPI) substrate was developed, which simultaneously possessed outstanding performance such as low square resistance (Rsq ∼ 12.7 Ω sq–1), high optical transmittance (T550 ∼ 86.3%), smooth surface (root-mean-square ∼ 0.32 nm), and excellent thermal, mechanical, and solution producing stability. Prior to the FTCE fabrication, four CPI samples with the number-average molecular weight ranging from 35.9 to 177.5 kDa were prepared and their optical, mechanical, and thermal properties were studied in detail. Moreover, the effect of the molecular weight on the minimum thickness that can withstand the following solution production of ultraflexible OSCs was investigated, which revealed that the molecular weight of CPI here should be above 81.4 kDa. Based on the FTCE, an ultraflexible OSC with a high PCE value of 14.37% and outstanding mechanical robustness was constructed, in which the PCE could still maintain above 96% of its initial value after 1000 bending cycles at a bending radius of 0.5 mm

Miscibility-Controlled Mechanical and Photovoltaic Properties in Double-Cable Conjugated Polymer/Insulating Polymer Composites

Flexibility is one of the main characteristics of organic solar cells (OSCs), which enables them to possess potential applications in flexible electronics. The study of flexibility (such as mechanical and bending behaviors) of the photoactive layers and the strategy to enhance the flexibility are important research topics in this field. In this work, we have focused on studying the flexibility of a single photoactive layer via using a double-cable conjugated polymer instead of two-component bulk-heterojunction layers. This simplified system enabled us to add the insulating polymers into the double-cable polymer to generate a polymer/polymer mixtures. The results found that the miscibility between the double-cable conjugated polymer and insulating polymers was the key factor to influence the mechanical and photovoltaic properties. Good miscibility by using polystyrene as an additive can provide better crack-onset strains as well as high efficiency, while lower miscibility by using polydimethylsiloxane as an additive exhibited low efficiencies in single-component OSCs

Double-Cable Conjugated Polymers with Rigid Phenyl Linkers for Single-Component Organic Solar Cells

Nonradiative recombination loss is the key factor to be responsible for low open-circuit voltage (Voc) in organic solar cells (OSCs), which can be reduced via tuning the chemical structure of conjugated materials. However, the intrinsic correlation between them was rarely studied. In this work, we were able to build a strong connection between chemical structure and nonradiative recombination loss, which was then used to lower the voltage losses in OSCs. The studies start from designing several double-cable conjugated polymers with rigid phenyl linkers, which guarantee the precise distance between donor (D) backbone and acceptor (A) side units. In addition, the number of phenyl linkers was changed from one to three, so as to provide different D/A distances. The universal studies of solar cells, morphology, and voltage losses showed that longer D/A distance provided lower nonradiative recombination losses and hence higher Voc in single-component OSCs. Our results demonstrate that extending the D/A distance via rigid phenyl linkers is an efficient way to reduce the voltage losses in OSCs

Miscibility-Controlled Mechanical and Photovoltaic Properties in Double-Cable Conjugated Polymer/Insulating Polymer Composites

Flexibility is one of the main characteristics of organic solar cells (OSCs), which enables them to possess potential applications in flexible electronics. The study of flexibility (such as mechanical and bending behaviors) of the photoactive layers and the strategy to enhance the flexibility are important research topics in this field. In this work, we have focused on studying the flexibility of a single photoactive layer via using a double-cable conjugated polymer instead of two-component bulk-heterojunction layers. This simplified system enabled us to add the insulating polymers into the double-cable polymer to generate a polymer/polymer mixtures. The results found that the miscibility between the double-cable conjugated polymer and insulating polymers was the key factor to influence the mechanical and photovoltaic properties. Good miscibility by using polystyrene as an additive can provide better crack-onset strains as well as high efficiency, while lower miscibility by using polydimethylsiloxane as an additive exhibited low efficiencies in single-component OSCs