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.

A thin film planar heterojunction organic photodetector (PHJ-OPD) is demonstrated. Different from a conventional sensitizer-doped photodetector, the limited spatial distribution of sensitizer in a PHJ-OPD enables significantly reduced thickness of the active layer without allowing the formation of unnecessary trap sites and electron percolation pathways. As a result, peak external quantum efficiency (EQE) of 120 700% and detectivity over 10 Jones are demonstrated with thin active layer thickness of 150 nm, which can be a significant benefit for high-resolution image sensor application. Furthermore, the operating voltage can be decreased to -5 V while maintaining high detectivity over 10 Jones. Remarkable thermal stability is also observed with minor change in detectivity for 2 h of continuous operation at 60 °C due to morphological robustness of PHJ. This work opens up a possibility of using a thin film PHJ-OPD as a key unit of high-resolution image sensor.

Here, we synthesized a dihexyloxynaphthalene-based conjugated polymer (PNa6-Th) to realize narrowband blue-selective polymer photodiode. The optical, electrochemical, and thermal properties of the synthesized polymer were investigated. It was found that PNa6-Th exhibited a blue-selective absorption with a narrow full width at half-maximum of ∼100 nm and a wide optical band gap of ∼2.52 eV. We constructed a planar heterojunction structure with PNa6-Th and ZnO as a blue-selective electron donor and nonabsorbing acceptor, respectively; To enhance the photodiode performance, a minor amount of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) was introduced on the donor layer. By introducing the PCBM on PNa6-Th layer, external quantum efficiency was increased from 5.4% for pristine device to 37.8% for 15 wt % PCBM-doped device, while the dark current values maintained nearly constant. This external quantum efficiency boost leads to high detectivity of 2.31 × 1012 Jones at −1 V. The physics behind the improved performance were fully discussed based on percolation pathway theory and space-charge-limited current analyses.