Dark Current Reduction Strategy via a Layer-By-Layer Solution Process for a High-Performance All-Polymer Photodetector

Abstract

The ideal bulk-heterojunction for high-performance organic photodetectors prefers a morphology with a vertically gradient component to suppress the leaking current. Here, we demonstrate an all-polymer photodetector with a segregated bulk-heterojunction active layer. This all-polymer photodetector exhibits a dramatically reduced dark current density because of its built-in charge blocking layer, with a responsivity of 0.25 A W–1 at a wavelength of approximately 600 nm and specific detectivity of 5.68 × 1012 cm Hz1/2 W–1 as calculated from the noise spectra at 1 kHz. To our knowledge, this is among the best performances reported for photodetectors based on both polymeric donor and acceptor in the photoactive layer. These findings present a facile approach to improving the specific detectivity of polymer photodetectors via a layer-by-layer solution process.

Vacuum‐Processed Small Molecule Organic Photodetectors with Low Dark Current Density and Strong Response to Near‐Infrared Wavelength

“…Therefore, it is not reasonable to utilize Equation (1) for estimating D*. Besides, we observed similar behavior of polymer photodetectors in other works, [51,55] implying that the equation for D* should be used as following [51,[53][54][55]…”

“…Specific detectivity, D*, of a photodetector determines its ability to detect the weakest photosignal under various noises such as shot, Johnson (thermal), and flicker (1/f). [12,19,22,[49][50][51][52][53][54] D* is a crucial figure of merit for photodetectors, which is usually expressed in the simple equation by [8][9][10][11][12][13][14][15][16][17][18]21,22,38,52,54,55]…”

All‐Polymer High‐Performance Photodetector through Lamination

“…This could be true when dark current is high (cases under reverse bias). Due to the difficulty of measuring the real noise, only quite a few papers24,31–34 have measured rather than estimated the noise. In these measurements, the noise was in fact far beyond shot noise limit and showing domination of 1/ f n noise ( n ≥ 1), which decreases dramatically with increasing frequency but sometimes can still be higher than shot noise even at 1 kHz.…”

Organic Photodetectors for Next‐Generation Wearable Electronics

“…not universally adopted, but instead many reports estimate D* based on only the shot noise and/or the thermal noise. [67] This simplification may lead to significant overestimation of the actual detectivity, [65,68] and makes it difficult to compare the performance of devices reported by different research groups.…”

“…Recently, Zhong et al reduced the dark (noise) current by using a layerbylayer (LBL) solution processing method. [68] As opposed to the conventional onestep solution method, where the donor and acceptor are processed from the same solution, the LBL approach first deposits the donor before processing the acceptor layer (Figure 3f-h). Although this is similar to how conventional planar heterojunction are made, in this case the donor and acceptor layers are not completely separated but instead they are able to partially mix in order to form BHJ mor phology while maintaining vertical segregation.…”