The semiconductor industry is undergoing rapid transformation to overcome the limits of transistor scaling and to meet the increasing demands of artificial intelligence and the Internet of Things. Neuromorphic devices that integrate flexibility, biocompatibility, and biodegradability offer new opportunities for sustainable, wearable, and implantable computing systems capable of seamless integration with biological environments, advancing the vision of green electronics. This review summarizes recent advances in flexible, biocompatible, and biodegradable materials for neuromorphic applications, highlighting their ability to emulate synaptic functions while maintaining mechanical compliance, biosafety, and environmental sustainability. We examine major material classes, including natural polymers, hydrogels, biocompatible metal oxides, and transient electronic systems, and discuss their roles in resistive switching, ionic–electronic conduction, and adaptive learning. Finally, we address the critical challenge of balancing high performance with biocompatibility and environmental friendliness, and we highlight emerging directions, such as multifunctional, self-healing, and energy-autonomous neuromorphic systems.

Active-matrix (AM) micro light-emitting diode (micro-LED) displays rely on transistors and capacitors, thereby limiting integration density, power efficiency, and manufacturing simplicity. While the monolithic integration of transistors onto micro-LED chips or complementary metal oxide semiconductor-based driving circuits has been investigated, these approaches still face challenges such as complex processing, unstable transistor performance, and dependence on capacitor-integrated thin-film transistor (TFT) backplanes. In this study, we present a capacitorless AM micro-LED display architecture driven by a germanium telluride memristor (GeTe memristor), monolithically integrated with the micro-LED chip. The GeTe memristor demonstrates multilevel switching, strong drive capability, and ultra-low operating voltages (SET < 0.2 V, RESET > −0.2 V) along with excellent thermal and electrical stability. Notably, its fabrication requires no thermal annealing, thus simplifying array-level integration compared to conventional TFT-based systems. Using the aforementioned architecture, we successfully demonstrated a capacitorless 12 × 12 AM micro-LED array capable of displaying alphabetic characters. This approach simplifies the manufacturing process and improves pixel density. Hence, the energy-efficient GeTe memristor offers a promising alternative to conventional TFT–capacitor configurations, thereby enabling the development of low-power, high-resolution display systems.

Flexible top-emission organic light-emitting diodes (f-TEOLEDs) with a high aperture ratio can be used in next-generation wearable electronic applications. However, the advancement of f-TEOLEDs is being hindered by their low light extraction and poor mechanical stability. In this study, we introduce an omnidirectional reflector (ODR) consisting of an Ag/SiO₂/Ta₂O₅ cylinder-embedded indium zinc oxide (IZO) mesh (c-mesh) structure that improves both the light extraction and mechanical flexibility of TEOLEDs using blue thermally activated delayed fluorescence emitters. The proposed ODR achieved a remarkable reflectance of over 96%, particularly in the transverse-electric mode. Furthermore, the Ta₂O₅ cylinders effectively compensated for the diverse void-induced depths in the IZO mesh, significantly reducing the leakage current between the electrode and the organic layers. In addition, the ODR electrodes exhibited outstanding mechanical stability. Moreover, even after being subjected to 2000 bending cycles over a 5 mm radius, the device luminance changed by less than 20%. Notably, the proposed f-TEOLEDs with Ag/SiO₂/c-mesh electrodes demonstrated superior performance, achieving a low turn-on voltage (2.6 V), high current efficiency (33 cd·A⁻¹), and power efficiency of 29.6 lm·W⁻¹. Finally, the devices featured a narrow full width at half maximum of 27 nm under first-order microcavity effects.