Universal Strategy To Reduce Noise Current for Sensitive Organic Photodetectors

Abstract

Low noise current is critical for achieving high-detectivity organic photodetectors. Inserting charge-blocking layers is an effective approach to suppress the reverse-biased dark current. However, in solution-processed organic photodetectors, the charge-transport material needs to be dissolved in solvents that do not dissolve the underneath light-absorbing layer, which is not always possible for all kinds of light-absorbing materials developed. Here, we introduce a universal strategy of transfer-printing a conjugated polymer, poly(3-hexylthiophene) (P3HT), as the electron-blocking layer to realize highly sensitive photodetectors. The transfer-printed P3HT layers substantially and universally reduced the reverse-biased dark current by about 3 orders of magnitude for various photodetectors with different active layers. These photodetectors can detect the light signal as weak as several picowatts per square centimeter, and the device detectivity is over 10 Jones. The results suggest that the strategy of transfer-printing P3HT films as the electron-blocking layer is universal and effective for the fabrication of sensitive organic photodetectors.

Light Detection in Open‐Circuit Voltage Mode of Organic Photodetectors

“…According to Figure S12, Supporting Information, a light intensity of 2.4 nW cm −2 is the LOD at −0.01 V. This value rises up to 12.6 nW cm −2 for the same device biased at −2 V. We note here that the lowest irradiance detectable at 0 V, 1.4 nW cm −2 , is underestimated since it is limited by the resolution of the experimental setup. Using lock‐in amplifier, researchers have claimed light intensity detection as weak as 7.6 pW cm −2 under short‐circuit current mode of OPD operation …”

“…This is frequently achieved by introducing additional interlayers into the device structure . Furthermore, detection of photocurrent in the picoampere range or below involves the use of shielded, high precision detection methods involving source‐measure units, lock‐in amplifiers, or spectrum analyzers …”

“…[16,18,19] Furthermore, detection of photocurrent in the picoampere range or below involves the use of shielded, high precision detection methods involving source-measure units, lock-in amplifiers, or spectrum analyzers. [20][21][22] Here, we present an alternative, easy-to-handle approach for low-light detection with OPDs. We demonstrate that using standard-structure OPDs, it is possible to accurately sense light intensity through changes in open-circuit voltage (V oc ).…”

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.…”

Ultraviolet Photodetectors Based on CH3NH3PbCl3 Perovskite Quantum Dots‐Doped Poly(triarylamine)

“…Armin et al fabricated large area of flexible organic photodetectors with suppressed dark current . Xiong et al fabricated highly sensitive organic photodetectors with reduced noise current . Wu et al reported an organic image sensor with photomultiplication .…”