Toward next‐generation electroluminescent quantum dot (QD) displays, inkjet printing technique has been convinced as one of the most promising low‐cost and large‐scale manufacturing of patterned quantum dot light‐emitting diodes (QLEDs). The development of high‐quality and stable QD inks is a key step to push this technology toward practical applications. Herein, a universal ternary‐solvent‐ink strategy is proposed for the cesium lead halides (CsPbX3) perovskite QDs and their corresponding inkjet‐printed QLEDs. With this tailor‐made ternary halogen‐free solvent (naphthene, n‐tridecane, and n‐nonane) recipe, a highly dispersive and stable CsPbX3 QD ink is obtained, which exhibits much better printability and film‐forming ability than that of the binary solvent (naphthene and n‐tridecane) system, leading to a much better qualitied perovskite QD thin film. Consequently, a record peak external quantum efficiency (EQE) of 8.54% and maximum luminance of 43 883.39 cd m−2 is achieved in inkjet‐printed green perovskite QLEDs, which is much higher than that of the binary‐solvent‐system‐based devices (EQE = 2.26%). Moreover, the ternary‐solvent‐system exhibits a universal applicability in the inkjet‐printed red and blue perovskite QLEDs as well as cadmium (Cd)‐based QLEDs. This work demonstrates a new strategy for tailor‐making a general ternary‐solvent‐QD‐ink system for efficient inkjet‐printed QLEDs as well as the other solution‐processed electronic devices in the future.

A Universal Ternary‐Solvent‐Ink Strategy toward Efficient Inkjet‐Printed Perovskite Quantum Dot Light‐Emitting Diodes

The use of Ti 3 C 2 T x MXenes/polyaniline composite tremendously improved the electrokinetic energy conversion efficiencies of nano-hydroelectric generators, demonstrating a power output sufficient to charge a commercial battery for the very first time. 

Towards Watt-scale hydroelectric energy harvesting by Ti3C2Tx-based transpiration-driven electrokinetic power generators

Nano-hydroelectric technology utilizes hydraulic flow through electronically conducting nanomaterials to generate electricity in a simple, renewable, ubiquitous, and environmentally friendly manner. To date, several designs of nano-hydroelectric devices have been devised to maximize the electrokinetic interactions between water molecules and nanomaterials. However, the reported power generation of the state-of-the-art nano-hydroelectric generators is not sufficient for practical use, as tens of thousands of units were required to operate low-power electronics on a mW scale. Here, we utilize titanium carbide (Ti3C2Tx) MXene nanosheets, which have advantageous properties including metal-like conductivity and hydrophilicity, to facilitate the electrokinetic conversion of the transpiration–driven electrokinetic power generator (TEPG) with a remarkably improved energy generation efficiency compared to that of carbon-based TEPG. The Ti3C2Tx MXene-based TEPG delivered a high pseudo-streaming current of 120 μA by the fast capillary flow promoted by MXene sheets coated on cotton fabric. The strong cationic affinity of Ti3C2Tx enables the generator to achieve an output of 0.68 V and 2.73 mA when NaCl solution is applied. Moreover, incorporation of a conducting polymer (i.e., Ti3C2Tx/polyaniline composite) enhanced the ionic diffusivity while maintaining the electrical network of Ti3C2Tx. The optimized Ti3C2Tx/polyaniline composite TEPG generated a maximum voltage of 0.54 V, a current of 8.2 mA, and a specific power density of 30.9 mW cm−3, which was sufficient to successfully charge a commercial Li-ion battery as well as low-power electronics and devices with a volume of 6.72 cm3.

/pdf/towards-watt-scale-hydroelectric-energy-harvesting-by-4vwqyfa5a2.pdf

Towards Watt-scale hydroelectric energy harvesting by Ti3C2Tx-based transpiration-driven electrokinetic power generators

Synergistic work of photo-thermoelectric and hydroelectric effects of hierarchical structure photo-thermoelectric textile for solar energy harvesting and solar steam generation simultaneously

Novel Narrow Bandgap Terpolymer Donors Enables Record Performance for Semitransparent Organic Solar Cells Based on All-Narrow Bandgap Semiconductors

Direct electricity generation from water flow/evaporation, coined hydrovoltaic effect, has recently attracted intense interest as a facile approach to harvest green energy from ubiquitous capillary water flow or evaporation. However, the current hydrovoltaic device is inferior in output power efficiency compared to other renewable energy devices. Slow water evaporation rate and inefficient charge collection at device electrodes are two fundamental drawbacks limiting energy output efficiency. Here, we report a bioinspired hierarchical porous fabric electrode that enables high water evaporation rate, efficient charge collection, and rapid charge transport in nanostructured silicon-based hydrovoltaic devices. Such an electrode can efficiently collect charges generated in nanostructured silicon as well as induce a prompt water evaporation rate. At room temperature, the device can generate an open-circuit voltage (Voc) of 550 mV and a short-current density (Jsc) of 22 μA·cm-2. It can output a power density over 10 μW·cm-2, which is 3 orders of magnitude larger than all those reported for analogous hydrovoltaic devices. Our results could supply an effective strategy for the development of high-performance hydrovoltaic devices through optimizing electrode structures.

Bioinspired Hierarchical Nanofabric Electrode for Silicon Hydrovoltaic Device with Record Power Output.

Coffee-Stain-Free Perovskite Film for Efficient Printed Light-Emitting Diode

In non-fullerene-based photovoltaic devices, it still remains unclear how excitons efficiently dissociate into free charge carriers even under a tiny driving force (tens of meV) with reduced energy loss. Here, dielectric constants of different non-fullerene-based solar cells consisting of fluorinated-thienyl benzodithiophene (BDT-2F)-based polymer PM6 as the typical donor, and a selected series of non-fullerene acceptors were precisely measured by a newly developed method. It was found that most of the non-fullerene acceptors exhibited higher dielectric constants than fullerene derivatives (PC61BM and PC71BM). The corresponding photoactive films exhibited not only higher dielectric constants but also the larger dielectric constant differences between donor and non-fullerene acceptors. These would result in lower exciton binding energy and increased charge dissociation possibility with low geminate losses. Additionally, the overlap between the emission spectrum of donor and absorption spectra of non-fullerene acceptors would allow the resonance energy transfer from donor to the acceptor in these non-fullerene-based devices, which was confirmed by investigating the emission spectra of pristine donor (and acceptor) films and corresponding blend films. Such an energy transfer process enhanced the efficient exciton diffusion, promising improved device performance. Therefore, based on the synergistic effect of higher dielectric property and energy transfer on charge separation of selected non-fullerene-based photovoltaic devices, these results provided strong hints to interpret efficient charge separation for the high device performance with a tiny driving force. Our work paves another path to elucidate the intrinsic physical working mechanism on non-fullerene organic solar cells.

Synergistic Effect of Dielectric Property and Energy Transfer on Charge Separation in Non-Fullerene-Based Solar Cells.

Hydrovoltaic devices are proposed as an alternative way to directly generate electricity due to the ubiquity of water and its interaction with specific porous structures. At present, the output power density of the reported device is limited by its low current density arising from the low surface charge density and inferior charge transport capability of the active materials. In this work, an asymmetric structure consisting of positively charged conductive polyaniline (PANI) and negatively charged Ti3C2TX MXene is proposed to build a hydrovoltaic device to achieve high conductivity and surface charge density simultaneously. An extra polyvinyl alcohol layer is utilized between PANI and MXene to reserve the asymmetric structure and maintain a constant voltage output. As a result, a peak current density of 1.8 mA/cm2 is achieved, which is 18 times higher than the previous peak current density of the device with an inert electrode. Our work of incorporating an asymmetric structure provides an alternative way to target high-efficiency hydrovoltaic devices with a large current density.

Zheheng Song

Papers

Bioinspired Hierarchical Nanofabric Electrode for Silicon Hydrovoltaic Device with Record Power Output.

Coffee-Stain-Free Perovskite Film for Efficient Printed Light-Emitting Diode

Synergistic Effect of Dielectric Property and Energy Transfer on Charge Separation in Non-Fullerene-Based Solar Cells.

Asymmetric Charged Conductive Porous Films for Electricity Generation from Water Droplets via Capillary Infiltrating.

Freestanding Silicon Nanowires Mesh for Efficient Electricity Generation from Evaporation-Induced Water Capillary Flow