Broadband, high-performance, p-type Bi₂Te₃ flakes photodetectors with multispectral imaging capability

Broadband photodetectors have received widespread attention due to their significant applications in optical communication, remote sensing, and imaging, especially in monolithic multispectral imaging and mimicking the human visual system. However, existing broadband materials struggle to simultaneously exhibit appropriate responses to blue (B), green (G), and red (R) wavelengths. In this work, we investigate the thickness-dependent work functions, contact properties, and broadband imaging photodetection performance of p-type Bi₂Te₃ flakes. It is found that the work functions of the flakes initially increase with thickness and stabilize at 5.07 eV when the thickness exceeding the critical screening length (about 6 nm). Device with Ag electrodes exhibits a hole-blocking layer and Schottky contact due to the lower work function of Ag compared to the p-type Bi₂Te₃ flakes, whereas higher work function metals such as Au and Pt form Ohmic contacts at the interfaces. Moreover, the p-type Bi₂Te₃ photodetector with Au contact demonstrates the highest responsivity of 141.77 mA W⁻¹ and detectivity of 1.04×10¹⁰ Jones, along with outstanding broadband photodetection from 405 to 1050 nm and multispectral imaging capability. This work not only provides guidance for optimizing electrode contacts in novel electronic devices but also highlights the promising potential of p-type Bi₂Te₃ flakes in multispectral imaging photodetection.