Lowering the Contact Barriers of 2D Organic F₁₆CuPc Field‐Effect Transistors by Introducing Van der Waals Contacts

Abstract

2D organic crystals exhibit efficient charge transport and field‐effect characteristics, making them promising candidates for high‐performance nanoelectronics. However, the strong Fermi level pinning (FLP) effect and large Schottky barrier between organic semiconductors and metals largely limit device performance. Herein, by carrying out temperature‐dependent transport and Kelvin probe force microscopy measurements, it is demonstrated that the introducing of 2D metallic 1T‐TaSe2 with matched band‐alignment as electrodes for F16CuPc nanoflake filed‐effect transistors leads to enhanced field‐effect characteristics, especially lowered Schottky barrier height and contact resistance at the contact and highly efficient charge transport within the channel, which are attributed to the significantly suppressed FLP effect and appropriate band alignment at the nonbonding van der Waals (vdW) hetero‐interface. Moreover, by taking advantage of the improved contact behavior with 1T‐TaSe2 contact, the optoelectronic performance of F16CuPc nanoflake‐based phototransistor is drastically improved, with a maximum photoresponsivity of 387 A W−1 and detectivity of 3.7 × 1014 Jones at quite a low Vds of 1 V, which is more competitive than those of the reported organic photodetectors and phototransistors. The work provides an avenue to improve the electrical and optoelectronic properties of 2D organic devices by introducing 2D metals with appropriate work function for vdW contacts.

Revealing and Controlling Energy Barriers and Valleys at Grain Boundaries in Ultrathin Organic Films

“…[ 36 ] While this drop‐casting method in its current form is not suitable for large‐scale processing, it is sufficient for the current investigations where sample dimensions below 1 cm 2 are required. The high purity of the resulting films is comparable to recent works focusing on low‐dimensional organic crystals as the active layer in, e.g., OFETs, [ 37–40 ] and allows precise examination of the surface potential of individual grain boundaries. In particular, this allows detailed local electrostatic examination of grain boundaries and thereby enables identification of the mechanisms by which grain boundaries can affect charge transport.…”

Improving Charge Injection at Gold/Conjugated Polymer Contacts by Polymer Insulator‐Assisted Annealing for Transistors

“…[22][23][24][25] Several methods have been proposed to reduce the contact resistance and improve charge injection at metal/organic interface, such as contact doping, introducing a charge injection layer, or forming an abrupt damage-free metal/semiconductor interface by transferred electrodes. [2,5,[24][25][26][27][28][29][30] However, these methods require additional and complicated processes, which increase the difficulty of device fabrication and some of them also…”

“…[ 22–25 ] Several methods have been proposed to reduce the contact resistance and improve charge injection at metal/organic interface, such as contact doping, introducing a charge injection layer, or forming an abrupt damage‐free metal/semiconductor interface by transferred electrodes. [ 2,5,24–30 ] However, these methods require additional and complicated processes, which increase the difficulty of device fabrication and some of them also damage organic films. [ 27 ] Actually, due to the dynamic impact of metal deposition process, the disordered metal/organic interface may be a thermodynamically non‐equilibrium state, which could be potentially reformed to construct a more ordered and stable structure spontaneously, thereby eliminating the adverse effects of metal deposition.…”

A Robust Bridge‐Type Airflow Sensor Based on Flexible Superhydrophobic Carbon Nanotube Fiber Thin Films

“…At the same time, the multi‐layer structure of CNTF leads to reduced layer distance of the bending part (Figure 5c), hence increasing Van de Waals contacting spots, further reducing contact potential barrier, and increasing conductivity. [ 46 ] The two corresponding resistances of contacting spots are together defined as contacting R cont . From the mechanism analysis above, conclusion can be drawn that applying on/off airflow onto the CNTF‐PPPS‐1 airflow sensor leads to distortion of the interior sensitive elements of the sensor, and thereby altering conductivity of the sensor, so that the airflow detection property is achieved.…”