Ultrasensitive broadband phototransistors based on perovskite/organic-semiconductor vertical heterojunctions

Abstract

Organolead halide perovskites have emerged as the most promising materials for various optoelectronic devices, especially solar cells, because of their excellent optoelectronic properties. Here, we present the first report of low-voltage high-gain phototransistors based on perovskite/organic-semiconductor vertical heterojunctions, which show ultrahigh responsivities of ~109A W–1 and specific detectivities of ~1014 Jones in a broadband region from the ultraviolet to the near infrared. The high sensitivity of the devices is attributed to a pronounced photogating effect that is mainly due to the long carrier lifetimes and strong light absorption in the perovskite material. In addition, flexible perovskite photodetectors have been successfully prepared via a solution process and show high sensitivity as well as excellent flexibility and bending durability. The high performance and facile solution-based fabrication of the perovskite/organic-semiconductor phototransistors indicate their promise for potential application for ultrasensitive broadband photodetection. High-gain phototransistors that operate from the ultraviolet to the near infrared could enable sensitive, broadband light detection. The excellent optoelectronic properties of organolead halide perovskites make them promising for various optoelectronic devices. Now, FY and co-workers from The Hong Kong Polytechnic University have fabricated low-voltage, high-gain phototransistors based on a vertical heterojunction consisting of a perovskite (CH3NH3PbI3-xClx) and an organic-semiconductor (PEDOT:PSS). Their high sensitivity is attributed mainly to the strong light absorption and long charge carrier lifetimes of the perovskite. The phototransistors can be fabricated on plastic substrates by solution processing, making them both flexible and compatible with cost-effective mass-production. Tests with light-emitting diodes that emit light at wavelengths of 370, 598 and 895 nanometers and a monochromator confirmed the broadband operation of the phototransistors.