2D Allotrope of Carbon for Self‐Powered, Flexible, and Transparent Optoelectronics

Flexible and transparent optoelectronics based on 2D materials are promising candidates for next‐generation technologies. Among all 2D materials, it is of numerous practical implications to explore nonmetal, earth‐abundant candidates. Herein, an exciting addition is unearthed—2D hydrogenized amorphous carbon (α‐C:H). The 2D α‐C:H nanosheets, with layered structural feature, are composed of crystalline sp2 nanoclusters embedded in sp3 amorphous matrix. The typical “vapor–solid” mechanism governs the growth of these nanosheets under the temperature–pressure combination above the Berman–Simon line. Their high transmittance over 97.7% covers the 425–1300 nm wavelength region. Optical characterizations also reveal a spectral overlap between the π–π* absorption edge and σ–σ* photoluminescence peak. Self‐powered and flexible photodetectors based on the 2D α‐C:H/ZnO heterostructure exhibit a remarkable photoresponse, with a broadened photosensitivity responsivity of 195.16 mA W−1 and a 267‐fold decrease of the rise time. This performance enhancement originates from the type II band alignment, the pyroelectric and piezo‐phototronic effects. As a new member in the 2D family, α‐C:H nanosheets promise to be appealing in transparent flexible optoelectronics with ultralow power consumption and real‐time, on‐site response.