Blue light emitting piezoelectric few-layered borophene nanosheets for flexible nanogenerators

Abstract

Piezoelectric response from two-dimensional layered materials with semiconducting properties is important for developing nanogenerators, piezotronics, and piezophototronics devices. However, experimental observation of piezoelectricity and semiconductor properties in monoatomic borophene has been a key challenge for the fabrication of nanogenerator devices. Here, we discover the non-centrosymmetric blue light emitting piezoelectric properties of few layered monoatomic borophene nanosheets. We develop the flexible piezoelectric nanogenerator using few layered borophene nanosheets in polydimethylsiloxane polymer, producing an output voltage of 8 V without electrical poling. The material exhibits a high piezoelectric charge coefficient (d33) of 86 pm V−1 and shows band gap opening with a high band gap of 2.32 eV. Surprisingly, the borophene nanosheets exhibit blue light emission under UV light illumination. Under UV light illumination, the device dramatically improves output performance. We find that the material exhibits a high dielectric constant of about 125 at low frequency.