Facile Tuning the Detection Spectrum of Organic Thin Film Photodiode via Selective Exciton Activation

Abstract

Here, we introduce a method of tuning the high-detectivity spectra of the organic photodiode (OPD) to fabricate a thin-film filter-less full-color image sensor. The strategically introduced PIN junction enables a selective activation of excitons generated from the photons with low extinction coefficient in the active layer such that the separated holes/electrons can contribute to the external current. In addition, we show that a well-defined PIN junction blocks the injection of nonallowed charge carriers, leading to very low dark current and near-ideal diode characteristics. Consequently, the high specific detectivity over 1.0 × 10 Jones are observed from R/G/B-selective thin-film OPDs.

Efficiency and spectral performance of narrowband organic and perovskite photodetectors: a cross-sectional review

“…Among small-molecule semiconductors, fullerenes have been central to the development of organic narrowband photodetectors, in view of their long-standing role as acceptor moieties par excellence. Their outstanding electron-accepting properties in BHJs and PHJs (in combination with polymeric and smallmolecule donors alike) have led to their widespread use in all types of narrowband photodetector configurations [19,30,31,[80][81][82][83][84][85]. However, their broad absorption tail through the visible has been problematic in some configurations (see section 6.3), and this has recently prompted the development of alternative small-molecule acceptors with narrowband absorption [11,[57][58][59][60][61] or with diverse onsets [42,[86][87][88].…”

“…Photons absorbed in the bulk of the donor layer are then dissipated (via exciton recombination), thus preventing them from delivering any photocurrent, and also from reaching the photoconversion volume at the interface with the acceptor. This leads to appreciable photoresponse only at wavelengths where the absorption spectra of the donor and acceptor do not overlap significantly [68,84]. Alternatively, the IOEF|PCL configuration can be attained by having a transport layer function as an internal optoelectronic filter [69,73,114].…”

“…As exemplified by figure 6(a), internally filtered and microcavity-based organic photodetectors generally feature lower EQE figures than their NBA counterparts (again, we refer to primary photocurrent operation due to its direct relationship to the intrinsic photoconversion capabilities of the photoactive material). Within the realm of internally filtered devices, the highest EQE of IntF-1 devices is at 13.6% [73]; IOEF|PCL generally perform below 30% [48,67,68,73,84,114,135] (with the exception of the work of Higashi et al which reaches 51% with an optimised architecture) [69]; CCN works typically give EQEs in the 1%-20% range [33,34,85,86,98] (the work of Arca et al reaching an EQE of 47%, is an important exception) [73]. The EQEs of most microcavity-based photodetectors are less or much less than 25% [42,65,[136][137][138][139] (the only exception being found in the work of Tang et al [42] who achieved EQEs up to 50% through detailed modelling and design).…”

“…Looking beyond NBA-type organic devices, green-selective organic photodetectors have achieved significantly narrow passbands (60-75 nm) via input filtering [80][81][82]. Internal filtering has been equally successful, with widths in the 60-80 nm range via IOEF|PCL [48,84,114], and down to 22 nm through CCN [86]. Green-selective microcavity-based devices have been demonstrated as capable of ultranarrowband photodetection (FWHM EQE at 35-50 nm) [136][137][138], provided that they are combined with input filtering to suppress their off-resonance response.…”

Light Detection in Open‐Circuit Voltage Mode of Organic Photodetectors

“…The extensive research on π‐conjugated materials over the last two decades has provided a better understanding of the light‐harvesting mechanisms in optoelectronic devices . Consequently, organic photodetectors (OPDs) show not only excellent quantum efficiency, and tunable spectral selectivity, but can also take advantage of photon up‐conversion, and photomultiplication mechanisms . Most importantly, organic semiconductor‐based sensors have closely approached the performance of conventional inorganic photodetectors demonstrating remarkable levels of responsivity, dark current, and even long‐term stability .…”