We establish a powerful poly(4-styrenesulfonate) (PSS)-treated strategy for sulfur vacancy healing in monolayer MoS2 to precisely and steadily tune its electronic state. The self-healing mechanism, in which the sulfur vacancies are healed spontaneously by the sulfur adatom clusters on the MoS2 surface through a PSS-induced hydrogenation process, is proposed and demonstrated systematically. The electron concentration of the self-healed MoS2 dramatically decreased by 643 times, leading to a work function enhancement of ∼150 meV. This strategy is employed to fabricate a high performance lateral monolayer MoS2 homojunction which presents a perfect rectifying behaviour, excellent photoresponsivity of ∼308 mA W−1 and outstanding air-stability after two months. Unlike previous chemical doping, the lattice defect-induced local fields are eliminated during the process of the sulfur vacancy self-healing to largely improve the homojunction performance. Our findings demonstrate a promising and facile strategy in 2D material electronic state modulation for the development of next-generation electronics and optoelectronics.

Monolayer 2D semiconductors (e.g., MoS2) are of considerable interest for atomically thin transistors but generally limited by insufficient carrier mobility or driving current. Minimizing the lattice defects in 2D semiconductors represents a common strategy to improve their electronic properties, but has met with limited success to date. Herein, a hidden benefit of the atomic vacancies in monolayer 2D semiconductors to push their performance limit is reported. By purposely tailoring the sulfur vacancies (SVs) to an optimum density of 4.7% in monolayer MoS2, an unusual mobility enhancement is obtained and a record‐high carrier mobility (>115 cm2 V−1 s−1) is achieved, realizing monolayer MoS2 transistors with an exceptional current density (>0.60 mA µm−1) and a record‐high on/off ratio >1010, and enabling a logic inverter with an ultrahigh voltage gain >100. The systematic transport studies reveal that the counterintuitive vacancy‐enhanced transport originates from a nearest‐neighbor hopping conduction model, in which an optimum SV density is essential for maximizing the charge hopping probability. Lastly, the vacancy benefit into other monolayer 2D semiconductors is further generalized; thus, a general strategy for tailoring the charge transport properties of monolayer materials is defined.

Paper-based (PB) green electronics is an emerging and potentially game-changing technology due to ease of recycling/disposal, the economics of manufacture and the applicability to flexible electronics. Herein, new-type printable PB strain sensors (PPBSSs) from graphite glue (graphite powder and methylcellulose) have been fabricated. The graphite glue is exposed to thermal annealing to produce surface micro/nano cracks, which are very sensitive to compressive or tensile strain. The devices exhibit a gauge factor of 804.9, response time of 19.6 ms and strain resolution of 0.038%, all performance indicators attaining and even surpassing most of the recently reported strain sensors. Due to the distinctive sensing properties, flexibility and robustness, the PPBSSs are suitable for monitoring of diverse conditions such as structural strain, vibrational motion, human muscular movements and visual control.

The NH4PbI3‐based phase transformation is realized by simply adding NH4I additive, in order to simultaneously control perovskite nucleation and crystal growth. Regarding the nucleation process, the NH4+ with small ionic radius preferentially diffuses into the [PbI6]4− octahedral layer to form NH4PbI3, which compensates the lack of CH3NH3I (MAI) precipitation. The generation of NH4PbI3 intermediate phase results in extra heterogeneous nucleation sites and reduces the defects derived from the absence of MA+. Regarding the crystal growth process, the cation exchange process between MA+ and NH4+, instead of the MAs directly entering, successfully retards the crystal growth. Such NH4PbI3 consumption process slows down the crystal growth, which effectively improves the perovskite quality with lowered defect density. The cooperation of these two effects eventually leads to the high‐quality perovskite with enlarged grain size, prolonged photoluminescence lifetime, lowered defect density, and increased carrier concentration, as well as the finally enhanced photovoltaic performance. Moreover, NH3 as a byproduct further facilitates the proposed transformation process and no external residue remains even without any post‐treatment. Such methodology of introducing a novel phase transformation to simultaneously control nucleation and crystal growth processes is of universal significance for further devotion in the foreseeable perovskite solar cells (PSCs) evolution.

van der Waals (vdWs) heterostructures have provided a platform for nanoscale material integrations and enabled promise for use in optoelectronic devices. Because of the ultrastrength of two-dimensional materials, strain engineering is considered as an effective way to tune their band structures and further tailor the interface performance of vdWs heterostructures. However, the less-constrained vdWs interfaces make the traditional strain technique via latticemismatched growth infeasible. Here, we report a strategy to construct mixed-dimensional heterostructure arrays with periodically strain-engineered vdWs interfaces utilizing one-dimensional semiconductor-induced nanoindentation. Using monolayer MoS 2 (1L-MoS 2 )/ZnO heterostructure arrays as a model system, we demonstrate inhomogeneous built-in strain gradient at the heterointerfaces ranging from 0 to 0.6% tensile. Through systematic optical characterization of the hybrid structures, we verify that strain can improve the interfacial charge transfer efficiency. Consequently, we observe that the photoluminescence (PL) emission of 1L-MoS 2 at strained interfaces is dramatically quenched more than 50% with respect to that at unstrained interfaces. Furthermore, we confirm that the strain-optimized interfacial carrier behavior is attributed to the reduction of interfacial barrier height, which originated from the strain-dependent Fermi level of 1L-MoS 2 . These results demonstrate that strain provides another degree of freedom in tuning the vdWs interface performance and our method developed here should enable flexibility in achieving more sophisticated vdWs integration via strain engineering.

Ultrathin molybdenum disulfide (MoS2) presents ideal properties for building next‐generation atomically thin circuitry. However, it is difficult to construct logic units of MoS2 monolayer using traditional silicon‐based doping schemes, such as atomic substitution and ion implantation, as they cause lattice disruption and doping instability. An accurate and feasible electronic structure modulation strategy from defect engineering is proposed to construct homogeneous electronics for MoS2 monolayer logic inverters. By utilizing the energy‐matched electron induction of the solution process, numerous pure and lattice‐stable monosulfur vacancies (Vmonos) are introduced to modulate the electronic structure of monolayer MoS2 via a shallow trapping effect. The resulting modulation effectively reduces the electronic concentration of MoS2 and improves the work function by 100 meV. Under modulation of Vmonos, an atomically thin homogenous monolayer MoS2 logic inverter with a voltage gain of 4 is successfully constructed. A brand‐new and practical design route of defect modulation for 2D‐based circuit development is provided.

The dangling-bond-free surfaces of van der Waals (vdW) materials make it possible to build ultrathin junctions. Fundamentally, the interfacial phenomena and related optoelectronic properties of vdW junctions are modulated by the interlayer coupling effect. However, the weak interlayer coupling of vdW heterostructures limits the interlayer charge transfer efficiency, resulting in low photoresponsivity. Here, a bilayer MoS2 homogeneous junction is constructed by stacking the as-grown onto the self-healed monolayer MoS2. The homojunction barrier of ∼165 meV is obtained by the electronic structure modulation of defect self-healing. This homojunction reveals the stronger interlayer coupling effect in comparison with vdW heterostructures. This ultrastrong interlayer coupling effect is experimentally verified by Raman spectra and angle-resolved photoemission spectroscopy. The ultrafast interlayer charge transfer takes place within ∼447 fs, which is faster than those of most vdW heterostructures. Furthermore, the homojunction photodiode manifests outstanding rectifying behavior with an ideal factor of ∼1.6, perfect air stability over 12 months, and high responsivity of ∼54.6 mA/W. Moreover, the interlayer exciton peak of ∼1.66 eV is found in vdW homojunctions. This work offers an uncommon vdW junction with strong interlayer coupling and perfects the relevance of interlayer coupling and interlayer charge transfer.

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