High-Speed Fabrication of Intrinsically Flexible Perovskite Optoelectronics on Diverse Substrates (Cellulose Paper, Textiles, etc.) Using Printing and Handwriting

Flexible optoelectronic devices on deformable substrates hold significant promise for applications in wearable electronics, soft robotics, deformable displays, and more. Despite extensive research into halide perovskites for high-performance light-emitting diodes (LEDs), existing fabrication techniques that use rigid substrates fail to meet the growing demand for flexible display electronics. This study introduces two all-solution-processed fabrication strategies for high-throughput production of intrinsically stretchable perovskite LEDs (PeLEDs), printing and handwriting. We firstly developed a highly scalable multi-material inkjet printing approach, each device layer, from the bottom anode to the top cathode, is directly patterned on elastomer such as PDMS.<br/><br/>Beyond elastomers, common materials such as cellulose paper and textiles show potential as platforms for next-generation flexible and wearable electronics. We introduce a novel fabrication methodology termed "handwriting," which is versatile, scalable, and sustainable. This method enables the direct drawing of multicolor PeLEDs (covering the entire visible spectrum) and perovskite photodetectors (PePDs, in both vertical-photodiode and planar-photoconductor configurations) on various unconventional substrates (including cellulose paper, textiles, plastic, rubber, metal, and 3D objects) in an ultra-fast and mask-free manner. This innovation leverages everyday ballpoint pens filled with specially formulated inks containing conductive polymer blends, metal nanowires, and perovskite/polymer composites for light emission and absorption.<br/><br/>To address the challenge of rough surface morphology on cellulose fiber networks, particularly to achieve uniform printed film thickness and minimal leakage current, we incorporated an ionic polymer, poly(ethylene oxide), into the inks. The rheology and viscosity of these formulated inks were meticulously adjusted to replicate an authentic writing experience. Furthermore, the handwriting method sets a new benchmark for the rapid production of high-performance perovskite optoelectronic devices, enabling the fabrication of a batch of samples within just 10 minutes—significantly faster compared to the hours or days required by conventional microfabrication processes. Notably, the entire process is conducted under ambient conditions without the need for specific moisture and temperature control. The PeLEDs produced via the handwriting method exhibit a brightness of up to 15,225 cd/m², a current efficiency of 6.65 cd/A, and a turn-on voltage of 2.4 V. The PePDs demonstrate an on/off ratio exceeding 10⁴ and a response time of less than 15 ms. Benefiting from the exceptional flexibility of each functional layer, the LEDs written on cellulose paper substrates can be bent to an extreme curvature radius of 1 mm for over 5000 cycles without any performance degradation. In summary, this work lays the foundation for the practical application of perovskite optoelectronics in cost-effective and large-area scenarios, such as E-textiles, E-paper, smart packaging, disposable electronics, and wearables.<br/><br/>References:<br/>1. Zhao, Junyi, et al. "Handwriting of perovskite optoelectronic devices on diverse substrates." <i>Nature Photonics</i> 17.11 (2023): 964-971.<br/>2. Zhao, Junyi, et al. "High-Speed Fabrication of All-Inkjet-Printed Organometallic Halide Perovskite Light-Emitting Diodes on Elastic Substrates." <i>Advanced Materials</i> 33.48 (2021): 2102095.