photocapacitors

Photocapacitors are energy storage devices in which light exposure influences charge storage in a capacitor-like structure. They rely on photoactive materials—such as semiconductors, quantum dots, dyes, or perovskites—whose absorption of photons generates electron-hole pairs or alters polarization. The generated charges are collected at electrodes to produce a stored electric energy, or the light-induced polarization effectively modulates the device capacitance.

The mechanisms fall into two broad categories. One is photo-induced polarization in a dielectric or semiconductor that yields a persistent charge separation, referred to as photocapacitance. The other involves photoelectrochemical charge storage, where photo-generated charges participate in redox reactions at interfaces. In solid-state designs, illumination can change the dielectric constant or carrier density, thereby changing capacitance or stored charge.

Architectures include solid-state capacitors with integrated photoactive layers, dye-sensitized or quantum-dot-based structures, and photoelectrochemical cells that are designed to be charged under light with either liquid electrolytes or solid contacts. Some devices pre-charge under illumination and then discharge to power a load, while others combine light harvesting and storage in a single unit.

Advantages of photocapacitors include the potential for charging from light, enabling self-powered operation for sensors or portable electronics. Limitations involve relatively modest energy density compared with batteries, stability and degradation under prolonged illumination, cycling durability in some chemistries, and limitations in spectral response.

Current research in photocapacitors focuses on improving efficiency, stability, and scalability, with potential applications in autonomous sensing, optoelectronic memory, and light-driven energy storage systems.