Broadband photovoltaic effect of n-type topological insulator Bi₂Te₃ films on p-type Si substrates

We report the photovoltaic effects of n-type topological insulator (TI) Bi₂Te₃ films grown on p-type Si substrates by chemical vapor deposition (CVD). The films containing large nanoplates with a smooth surface formed on p-Si exhibit good p–n diode characteristics under dark and light illumination conditions and display a good photovoltaic effect under the broadband range from ultraviolet (UV) to near infrared (NIR) wavelengths. Under the light illumination with a wavelength of 1, 000 nm, a short circuit current (I_SC) of 19.2 μA and an open circuit voltage (V_OC) of 235 mV are achieved. The maximum fill factor (FF) increases with a decrease in the wavelength or light density, achieving a value of 35.6% under 600 nm illumination. The photoresponse of the n-Bi₂Te₃/p-Si device can be effectively switched between the on and off modes in millisecond time scale. These findings are important for both the fundamental understanding and solar cell device applications of TI materials.