Flexible Broadband Photodiodes Based on Amorphous Te_0.4Se_0.6 Thin Films

Abstract

Crystalline selenium-based photodiodes possess a photoresponse covering the range from 300 to 700 nm, low dark current, and high power conversion efficiency, making them suitable for thin-film photovoltaics and photodetection. In addition, the Te x Se 1−x alloy has emerged as a promising candidate for photodetection with extended and tunable absorption in up to short-wavelength infrared. However, the devices based on the Te x Se 1−x alloy suffer from large dark and noise currents, low on−off ratios, limited linear dynamic ranges, and the requirement for high annealing temperature. In this work, we successfully fabricated high-quality amorphous Te 0.4 Se 0.6 films by using thermal evaporation without further annealing. Then, we systematically investigated the fundamental properties of these amorphous Te 0.4 Se 0.6 thin films. Furthermore, we fabricated flexible photodiodes, which exhibited state-of-the-art performance, including high on−off ratios exceeding 10 5 and an ultralow dark current close to 10 −8 A cm −2 at −0.5 V, a large LDR of 125 dB, and a fast response time of <5 μs. Furthermore, prototypical devices based on amorphous Te 0.4 Se 0.6 thin films were also introduced for photoplethysmography and light communication, highlighting the great potential for real applications.