P-doped organic semiconductor: Potential replacement for PEDOT:PSS in organic photodetectors

Abstract

In this work we present an alternative to the use of PEDOT:PSS as hole transport and electron blocking layer in organic photodetectors processed by solution. As PEDOT:PSS is known to be sensitive to humidity, oxygen and UV, removing this layer is essential for lifetime improvements. As a first step to achieving this goal, we need to find an alternative layer that fulfills the same role in order to obtain a working diode with similar or better performance. As a replacement, a layer ofis used. This p-doped layer effectively lowers the hole injection barrier, and the low electron affinity of the polymer prevents the injection of electrons in the active layer. We show similar device performance under light and the improvements of detection performance with the doped layer in comparison with PEDOT:PSS, leading to a detectivity of 1.9x10 13 cm(Hz) 1/2 (W) -1 , competitive with silicon diodes used in imaging applications. Moreover, contrary to PEDOT:PSS, no localization of the p-doped layer is needed, leading to a diode active area defined by the patterned electrodes.Photodetectors based on organic active layers have shown significant advantages over the past decade. The use of polymers instead of inorganic materials like silicon or germanium leads to a strong reduction in processing cost and opens possibilities for applications on large area, flexible and transparent substrates 1-4 . Today, organic devices exhibit good electrical performance and can compete with amorphous silicon, but improvements need to be made to increase their lifetime. ____________________________ a)

Superior Noise Suppression, Response Time, and Device Stability of Non‐Fullerene System over Fullerene Counterpart in Organic Photodiode

“…For this reason, all previous researches reported the OPD structure including EBL. [34][35][36][37] Thus, we tried to form high anodic barrier energy to suppress of dark current by forming the direct tunneling using two different acceptor materials with different LUMO energy level. Figure S6, Supporting Information, shows the working principle of the OPD devices with PC 71 BM and eh-IDTBR in dark conditions with a reverse bias.…”

The formation of polymer-dopant aggregates as a possible origin of limited doping efficiency at high dopant concentration

“…S1 (a)). As an ohmic contact is formed with doping [18], we expect the contact resistance to decrease. Moreover, a TLM analysis on a 5% MR doped sample exhibits a contact resistance 4 orders of magnitude lower than the bulk resistance (supplementary information , FIG.…”

Insights into the Failure Mechanisms of Organic Photodetectors

“…These results are essentially the consequence of the low dark current (0.3 nA cm −2 at −2 V) achieved thanks to the excellent control of energetic barriers at the electrodes. The energetic barriers were controlled by the introduction of PEIE and PEDOT:PSS organic materials, as reported in the work of Pierre et al [6] In the literature, other approaches were also implemented to reduce dark current in organic photodiodes, one can cite the transfer-printing of the P3HT conjugated polymer, [7] , the introduction of p-doped layer by using a soft contact transfer lamination, [8] the use of a double electron blocking layer, [9] or the introduction of anionic polyelectrolyte as cathode interlayer. [10] It is important to note that the performances of organic photodiodes are comparable with their inorganic counterparts in terms of dark current, responsivity and detectivity.…”