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Full‐Color Retinal Prosthetic Optoelectronic organic polymers are employed as functional material substitutes for photoreceptor cells towards a state‐of‐the‐art full‐color retinal prosthetic with the aim of potentially restoring vision in individuals afflicted with retinal disorders such as age‐related macular degeneration and retinitis pigmentosa. More details can be found in article 2400128 by Leslie Askew, Aimee Sweeney, David Cox, and Maxim Shkunov.

Recent research on synergistic integration of photoelectric energy conversion and electrochemical energy storage devices has been focused on achieving sustainable and reliable power output. The energy conversion device (solar cells), when integrated with energy storage systems such as supercapacitors (SC) or lithium-ion batteries (LIBs), can self-charge under illumination and deliver a steady power supply whenever needed. This review highlights the progress in the development of various self-charging power packs with a supercapacitor as an energy storage system in detail. This integrated assembly is often referred to as a self-charging power pack, photocapacitor, or solar capacitor. Herein, a supercapacitor is chosen as the energy storage unit, since it is capable of providing high power density and long-term stability. In order to utilize these power packs in practical applications, various factors are considered, including overall energy conversion efficiency, fabrication techniques, safety, and the cost of the device. In the present review, various device configurations, operation mechanisms, and performance of several photocapacitors are presented. Finally, the existing challenges and limitations of self-charging power packs are elaborated.

Implantable devices for the wireless modulation of neural tissue need to be designed for reliability, safety and reduced invasiveness. Here we report chronic electrical stimulation of the sciatic nerve in rats by an implanted organic electrolytic photocapacitor that transduces deep-red light into electrical signals. The photocapacitor relies on commercially available semiconducting non-toxic pigments and is integrated in a conformable 0.1-mm 3 thin-film cuff. In freely moving rats, fixation of the cuff around the sciatic nerve, 10 mm below the surface of the skin, allowed stimulation (via 50–1,000-μs pulses of deep-red light at wavelengths of 638 nm or 660 nm) of the nerve for over 100 days. The robustness, biocompatibility, low volume and high-performance characteristics of organic electrolytic photocapacitors may facilitate the wireless chronic stimulation of peripheral nerves. An organic electrolytic photocapacitor transducing deep-red light into electrical signals and implanted within a thin cuff around the sciatic nerve of rats allows for wireless electrical stimulation of the nerve for over 100 days.

Bioinspired supramolecular architectonics is attracting increasing interest due to their flexible organization and multifunctionality. However, state‐of‐the‐art bioinspired architectonics generally take place in solvent‐based circumstance, thus leading to achieving precise control over the self‐assembly remains challenging. Moreover, the intrinsic difficulty of ordering the bio‐organic self‐assemblies into stable large‐scale arrays in the liquid environment for engineering devices severely restricts their extensive applications. Herein, a gaseous organization strategy is proposed with the physical vapor deposition (PVD) technology, allowing the bio‐organic monomers not only self‐assemble into architectures well‐established from the solvent‐based approaches but morphologies distinct from those delivered from the liquid cases. Specifically, 9‐fluorenylmethyloxycarbonyl‐phenylalanine‐phenylalanine (Fmoc‐FF) self‐assembles into spheres with tailored dimensions in the gaseous environment rather than conventional nanofibers, due to the distinct organization mechanisms. Arraying of the spherical architectures can integrate their behaviors, thus endorsing the bio‐organic film the ability of programmable optoelectronic properties, which can be employed to design P‐N heterojunction‐based bio‐photocapacitors for non‐invasive and nongenetic neurostimulations. The findings demonstrate that the gaseous strategy may offer an alternative approach to achieve unprecedented bio‐organic superstructures, and allow ordering into large‐scale arrays for behavior integration, potentially paving the avenue of developing supramolecular devices and promoting the practical applications of bio‐organic architectonics. By eliminating solvophobic driving forces and solvent interference, a physical vapor deposition based gaseous organization strategy is delivered, allowing Fmoc‐FF self‐assemble into spheres with tailored dimensions. Furthermore, arraying of the spheres can integrate their behaviors, endorsing the bio‐organic film the ability of programmable optoelectronic properties, which can be employed to design P‐N heterojunction‐based bio‐photocapacitors for non‐invasive and nongenetic neurostimulations.

Light activated local stimulation and sensing of biological cells hold great promise for minimally invasive bioelectronic interfaces. Organic semiconductors are particularly appealing for these applications due to their optoelectronic properties and biocompatibility. This study examines the material properties necessary to localize the optical excitation and achieve optoelectronic transduction with high spatial resolution. Using photovoltage and photocurrent microscopy, we investigate spatial broadening of local optical excitation in Phthalocyanine/3,4,9,10‐Perylenetetracarboxylic diimide (H2PC/PTCDI) planar heterojunctions. Our measurements reveal that resolution losses are tied to the effective diffusion length of charge carriers at the heterojunction. For the H2PC/PTCDI heterojunction, the diffusion length is determined to be λd = 1.5 ± 0.1 µm, attributed to reduced carrier mobility. Covering the heterojunction with poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) improves the charge generation performance but increases the carrier diffusion length to λd = 7.0 ± 0.3 µm due to longer lifetime and higher carrier mobility. These findings elucidate the physical mechanisms underlying transduction and provide design principles for organic semiconductor devices aimed at achieving high efficiency and high spatial resolution for wireless and optically activated bioelectronics. This study explores how the optoelectronic properties of organic semiconductors impact on the resolution of light‐activated bioelectronic interfaces. Using photovoltage and photocurrent microscopy techniques, the authors show that H2PC/PTCDI heterojunctions enable a resolution down to 6.5 µm due to low carrier mobility along the heterojunction. Adding a layer of PEDOT:PSS increases charge separation efficiency, but deteriorates the resolution due to larger photocarrier diffusion.

For the prosthetic retina, a device replacing dysfunctional cones and rods, with the ability to mimic the spectral response properties of these photoreceptors and provide electrical stimulation signals to activate residual visual pathways, can relay sufficient data to the brain for interpretation as color vision. Organic semiconductors including conjugated polymers with four different bandgaps providing wavelength‐specific electrical responses are ideal candidates for potential full‐color vision restoration. Here, conjugated polymer photocapacitor devices immersed in electrolyte are demonstrated to elicit a photovoltage measured by a Ag/AgCl electrode 100 microns from the device of ≈−40 mV for 15–39 µW mm−2 of incident light power density at three wavelengths: 405 nm for blue photoreceptor candidate material, 534 nm for green, 634 nm for red. Photoresponse is substantially improved by introducing polymer donor/acceptor molecules bulk heterojunctions. Devices with bulk heterojunction configurations achieved at least −70 mV for green candidates with the highest at −200 mV for red cone candidates. These findings highlight the potential for organic materials to bridge the gap toward natural vision restoration for retinal dystrophic conditions such as age‐related macular degeneration, Stargardt disease, or retinitis pigmentosa and contribute to the ongoing advancements in visual prosthetic devices. Optoelectronic organic polymers are employed as functional material substitutes for photoreceptor cells toward a state‐of‐the‐art full‐color retinal prosthetic. The objective of this study is to assess the viability of emulating the functionality of natural photoreceptors using these specialized materials, with the aim of potentially reinstating vision in individuals afflicted with retinal disorders.

Fiber-shaped photocapacitors (FPCs) based on shared bifunctional fiber electrodes for supercapacitors and solar cells hold great potential for the realization of self-powered systems for flexible wearable electronics. However, the reported electrodes for FPCs still face certain limitations, such as limited specific energy density, low total photochemical–electric energy conversion efficiency ( η total ), and poor flexibility. Herein, hollow fibers consisting of partially reduced graphene oxide and a highly conductive polymer are assembled by wet-spinning and employed as shared bifunctional fibers to fabricate self-powered FPCs. Intriguingly, the FPCs achieve high flexibility and a η total of 4.2%. This study illustrates a feasible way to design high-performance FPCs and their applications in flexible electronics. Graphical Abstract

The LC oscillator with the interdigitated aluminium-on-GaN/sapphire photocapacitor has been demonstrated. Upon illumination with a 375 nm UV LED, an oscillator frequency downshift owing to the photocapacitive effect attains a 5.2 MHz (3.5 % of the dark frequency value 149 MHz) with sensitivity up to 170 kHz/(μW/cm2). The oscillator can be employed as a visible-blind UV sensor with a remote wireless pickup of the RF output signal.

The novel metallo-phthalocyanines (4–6) were obtained from the reactions of gereniol substituted phthalonitrile compound (3) with corresponding metal salts (Co (II), Cu (II) and Zn (II) acetates). The electrical and photoconductive properties of Al/p-Si/organic complex/Al devices with cobalt (4) , copper (5) and zinc (6) phthalocyanines complexes containing geraniol as side groups were studied by using optoelectrical measurements at various sunlight intensites. The transient photocurrent and photocapacitance were measured as a function of time. Experimental results indicate that the prepared diodes exhibit both photodiode and photocapacitive behavior. Consequently, it is evaluated that the studied devices can be used as a photocapacitor in optical applications.

Photocapacitors gain increasing attention due to their capability of integrating conversion and storage of solar energy which can realize miniaturization and multi-functionalization of the device. In this work, a photoresponsible and reliable electrode consisting of Al- and Fe-doped TiO 2 (Al, Fe–TiO 2 ), SiO 2 and C with vertically aligned nanopores structure is developed on a pentabasic ceramic substrate of Al- and Fe-doped Ti 3 SiC 2 (Al, Fe–TSC) via sintering and anodizing in sequence. The resulting electrode demonstrates good electrochemical performance with a specific capacitance of 12.03 mF cm −2 at the scan rate of 100 mV s −1 and sustains a stability of 93% after 1000 cycles. Moreover, it exhibits a high solar energy conversion and storage capacity up to 59 μA cm −2 and 4.33 mF cm −2 under visible light irradiation indicating that it has the potential to be used as a photocapacitor. The exploited approach in this work offers an alternative strategy for designing miniaturized difunctional photoelectrode ingredients with ordered periodic nanostructure to promote solar harvesting and utilizing of the photocapacitor.