▎ 摘　　要

Graphene is flexible and transparent with one-atom layer thickness, and is a novel building block with potential applications in future portable devices. Herein a flexible, transparent and ultrathin earphone based on single-layer graphene (SLG) is reported. The SLG earphone operates in the frequency range of 20 Hz to 200 kHz and has a highest sound pressure level (SPL) of 70 dB at a 1 cm distance. The SPLs emitted from one to six layers of stacked SLG are compared. It is observed that the SPL decreases with an increasing number of stacked layers. The SLG earphone, which is packaged with a commercial earphone casing, can play music clearly. Compared with a conventional earphone, the SLG earphone has a broader frequency response and a lower fluctuation. Testing results in both time and frequency domains show a frequency doubling effect, which indicates that the working principle is based on the electro-thermoacoustic (ETA) effect. As the SLG earphone operates in both the audible and ultrasonic frequency range, it can be used for a wide variety of applications.