High-Performance\nAll-Polymer Photodetectors via a\nThick Photoactive Layer Strategy

Abstract

To\nachieve high detectivity in all-polymer photodetectors (all-PPDs),\na thick-film photoactive layer is favored because it can effectively\nsuppress the dark current density. However, if the photoactive layer\nof the film is too thick, it leads to reduced responsivity owing to\nincreased recombination loss. We developed high-performance all-PPDs\nby using a narrowband-gap p-type polymer NT40 and an n-type polymer\npoly­{[<i>N</i>,<i>N</i>′-bis­(2-octyldodecyl)-naphthalene-1,4,5,8-bis­(dicarboximide)-2,6-diyl]-<i>alt</i>-5,5′-(2,2′bithiophene)} as the photoactive\nlayer. The high charge carrier mobility of both copolymers enabled\na photoactive layer thickness of 300 nm, leading to an ultralow dark\ncurrent density of 4.85 × 10^–10 A cm^–2, a detectivity of 2.61 × 10¹³ Jones, a high responsivity\nof 0.33 A W^–1 at 720 nm, and a bias of −0.1\nV. The detectivity achieved >10¹³ Jones in a wide range\nfrom 360 to 850 nm, which is among the highest values so far reported\nfor all-PPDs without extra gains. More importantly, the resultant\nall-PPDs exhibited a high working frequency over 10 kHz associated\nwith a large linear dynamic range. These findings demonstrate great\npotential for practical applications of the all-PPDs developed in\nthis work.