Flexible Organic Photodetectors with Mechanically Robust Zinc Oxide Nanoparticle Thin Films

Abstract

Zinc oxide nanoparticle (ZnO-NP) thin films have been intensively used as electron transport layers (ETLs) in organic optoelectronic devices, but their moderate mechanical flexibility hinders their application to flexible electronic devices. This study reveals that the multivalent interaction between ZnO-NPs and multicharged conjugated electrolytes, such as diphenylfluorene pyridinium bromide derivative (DFPBr-6), can significantly improve the mechanical flexibility of ZnO-NP thin films. Intermixing ZnO-NPs and DFPBr-6 facilitates the coordination between bromide anions (from the DFPBr-6) and zinc cations on ZnO-NP surfaces, forming Zn 2+ −Br − bonds. Different from a conventional electrolyte (e.g., KBr), DFPBr-6 with six pyridinium ionic side chains holds the Br − -chelated ZnO-NPs adjacent to DFP + through Zn 2+ −Br − −N + bonds. Consequently, ZnO-NP:DFPBr-6 thin films exhibit improved mechanical flexibility with a critical bending radius as low as 1.5 mm under tensile bending conditions. Flexible organic photodetectors with ZnO-NP:DFPBr-6 thin films as ETLs demonstrate reliable device performances with high R (0.34 A/W) and D* (3.03 × 10 12 Jones) even after 1000 times repetitive bending at a bending radius of 4.0 mm, whereas devices with ZnO-NP and ZnO-NP:KBr ETLs yield >85% reduction in R and D* under the same bending condition.

Flexible and Stretchable Light-Emitting Diodes and Photodetectors for Human-Centric Optoelectronics

“…Similarly, the nanoscale thinning process and structural design, including serpentine, − fractals, − buckling, − and liquid metals, − have been explored for developing flexible and stretchable electrodes. For active materials, several approaches, including nanodimensional materials, , structural engineering, ,− organic materials ,− and hybrid composites, − are introduced to implement the PDs with great flexibility/stretchability and high performance simultaneously. Representative flexible/stretchable PDs with performance parameters are summarized in Table .…”

Submicron-Thickness Ultraflexible Organic Light-Emitting Diodes via a Photoregulated Stripping Strategy

“…Ultraflexible electronics possess extremely lightweight, thin, and soft properties, enabling seamless contact with curved and moving surfaces, as well as compatibility with human skin and internal organs, showing significant application prospects in the development of epidermal and implantable electronics. − In response to this trend, several notable ultraflexible electronic devices have already been developed, such as organic thin-film transistors (OTFTs), , organic photovoltaics (OPVs), , organic photodetectors (OPDs), , and organic light-emitting diodes (OLEDs). , Among them, OLEDs as typical carriers of visual information transmission are considered to be one of the most potential candidates for emerging ultraflexible displays, due to their unique advantage of inherent flexibility, high contrast, and wide viewing angle. , Recently, although numerous research efforts have focused on flexible OLEDs, the development of ultraflexible OLEDs is still initial and scarce. However, compared to flexible OLEDs, achieving ultraflexible counterparts is extremely critical for the preparation of mechanically stable foldable and skin electronics.…”

Flexible Self‐Powered Organic Photodetector with High Detectivity for Continuous On‐Plant Sensing

“…[27][28][29][30][31] Organic photovoltaics have been demonstrated in ultrathin form factors with a powerto-weight density far greater than Si-based devices. [32] This opens up opportunities for the detectors to conform to non-planar surfaces, [28,33,34] and surfaces that cannot bear the weight of heavy objects (e.g., a leaf). Flexible OPDs have been fabricated utilizing flexible conductive electrodes with polyethylene terephthalate (PET), [35] polyimide, [33,36] and polyethylene naphthalate substrates.…”

“…[32] This opens up opportunities for the detectors to conform to non-planar surfaces, [28,33,34] and surfaces that cannot bear the weight of heavy objects (e.g., a leaf). Flexible OPDs have been fabricated utilizing flexible conductive electrodes with polyethylene terephthalate (PET), [35] polyimide, [33,36] and polyethylene naphthalate substrates. [37] However, they typically exhibit performance below that of rigid detectors, [35] remain limited in the degree of flexibility, [33,37] or require a voltage bias for effective operation.…”

“…Flexible OPDs have been fabricated utilizing flexible conductive electrodes with polyethylene terephthalate (PET), [35] polyimide, [33,36] and polyethylene naphthalate substrates. [37] However, they typically exhibit performance below that of rigid detectors, [35] remain limited in the degree of flexibility, [33,37] or require a voltage bias for effective operation. [36] Here, we demonstrated a flexible self-powered OPD capable of stable, robust, long-term detection.…”