Diminished Trap-Induced Leakage Current at the Organic/Electrode Interface for High-Performance Organic Photodetectors

Abstract

The influence of the absence of a π-conjugated polymer-based charge-blocking layer (CBL) or interlayer between the photoactive layer/electrode interface in organic photodetectors (OPDs) is investigated. As compared to devices with a chargeblocking layer, OPDs with a metal/photoactive layer/metal sandwich structure exhibit similar external quantum efficiency but lower dark current density hence a higher specific detectivity (D*). The decrease in dark current density in devices without a CBL can be attributed to the elimination of additional trap states in the CBL, provided that a large charge injection barrier is maintained at the metal/active layer interface. In a device with the CBL, a clear dependence between the density of trap states (tDOS) and the magnitude of dark current density is verified. As such, suppressing undesired injection and trap-induced leakage current may cancel each other out in the device with a CBL. By evaluating the trap-induced leakage of current, we proposed that the key to obtain high specific detectivity in OPDs is to use a charge-blocking layer with low trap density or to use a CBL-free device structure.

Double-Side Selective Spectral Response Organic Photodetectors for Demultiplexing Optical Signals

“…With this unique device structure, wavelength-selective (narrowband) detection can be realized via manipulation of exciton distribution and thus the internal quantum efficiency (IQE), while multicolor detection can be achieved by employing a different detection window (Figure b, the validity of the approach will be discussed below), in contrast to what is seen in the bulk heterojunction (BHJ) device, where exciton distribution within the active layer follows an exponential decay as a result of Beer–Lambert absorption (Figure c) and the vast majority of carriers cannot be extracted due to low mobility and large layer thickness. Moreover, benefiting from its well-defined interface and diminished trap-induced leakage current at the organic/electrode interface, this buffer-layer-free device structure is considered as a promising candidate for suppressing leakage current …”

“…Moreover, benefiting from its well-defined interface and diminished trap-induced leakage current at the organic/ electrode interface, this buffer-layer-free device structure is considered as a promising candidate for suppressing leakage current. 28 Figure 2a shows the responsivity spectra of a typical PHJ device under −1 V reverse bias. Under top illumination condition (using cathode as the incident light window), good photoresponse in the range of 350−600 nm is clearly seen, while photoresponse to a longer wavelength is weak, with a maximal spectral responsivity of 51 and 11 mA W −1 , respectively.…”

Ultranarrow-bandgap small-molecule acceptor enables sensitive SWIR detection and dynamic upconversion imaging

“…Here, to explore the impact of trap states on the device performance, we meticulously profiled the density and energy distribution of trap states in the ATT-X-F in photodiode by Mott-Schottky analysis and thermal admittance spectra. For comparison, PTB7-Th:PC 71 BM–based photodiode was fabricated and the same device geometry with ITO/PEDOT:PSS/PTB7-Th:acceptor/PDINN/Ag was adopted for the purpose of excluding the influence of interface-induced trap states ( 51 , 52 ). As shown in Fig.…”