All‐Sprayed‐Processable, Large‐Area, and Flexible Perovskite/MXene‐Based Photodetector Arrays for Photocommunication

Photodetectors (PDs) for photoelectric signal conversion are attracting an increasing attention in scientific research and industrial realms due to its wide applications, such as optical communications, environmental monitoring, and biological detection.[1] Currently, the widely used active materials of PDs are dominated by crystalline-Si and III–V alloys for the detection of ultraviolet (UV) to near-infrared spectra.[2] However, the above PDs are usually assembled on rigid substrates, which seriously limits its wider applications in the field of flexible optoelectronics devices, such as wearable optoelectronic devices, bendable imaging sensors, and implantable optoelectronics devices.[3] Contrary to rigid PDs, flexible PDs can essentially meet the stretchable and bendable demands for intelligentized applications. Both high optoelectronic performance and excellent mechanical flexibility should be simultaneously integrated in one device, which is still a great challenge for the active materials, electrodes, substrates and fabrication technique to date.[4] Therefore, in order to obtain the flexible PDs with the above two advantages, the as-prepared devices must meet the following requirements: i) the sufficiently thin active materials for effectively releasing stress together with the relatively low degradation of photoelectrical properties when bending; ii) the well-matched work function between the optimal electrode materials and active materials in order to effectively transport photogenerated electron–hole pairs; and iii) the low-cost, large-area, and easy-processable fabrication techniques for promisingly replacing the expensive and complex high-vacuum process technology.[5] Recently, all-inorganic perovskites (CsPbX3) are hopeful to be widely used in optoelectronics devices due to the unique photoelectric properties, such as large absorption coefficient (2 × 105 cm−1), high charge carrier mobility (1000 cm2 V−1), long electron–hole diffusion, and tunable bandgap.[6] Particularly, compared to traditional crystalline-Si, all-inorganic perovskites can be processed by more economical solution-processing Flexible photodetectors (PDs) are attracting more attention due to their promising applications in wearable optoelectronic devices, bendable imaging sensors, and implantable optoelectronics. For the easy-processable technology of massively fabricating PDs, instead of the expensive and complex high-vacuum technique, the well-matched work function of their active materials is essential. Herein, all-sprayed-processable and largearea PDs are demonstrated on common paper based on two-dimensional (2D) CsPbBr3 nanosheets and conductive Ti3C2Tx (MXene). Ascribed to the superior conductivity of MXene, high crystallinity of 2D CsPbBr3, and their well-matched work function, the as-prepared PDs exhibit an outstanding on/off current ratio up to 2.3 × 103 and a remarkable photoresponse as fast as 18 ms. Specifically, the detectivity (D*) of 6.4 × 108 Jones and responsivity (R) of 44.9 mA W−1 under a bias of 10 V are achieved. Besides, after bending 1500 cycles, the as-prepared PDs can still maintain the excellent flexibility and stability. Based on this, a superior-quality and large-area 1665 pixel sensor in 72 cm2 (≈24 units cm−2) is developed, and it can clearly transmit the image of “0” to realize the photocommunication function. This work provides a low-cost method of massively producing the flexible large-area PDs for wearable optoelectronic devices and expanded photocommunication.