a green-selective (G) OPD layer on top of blue (B) and red (R) color filters. Removing the G filter in the horizontally integrated R/G/B color filters resulted in a 1.5-fold increase in image resolution. [4] Siegmund et al. achieved narrowband near-infrared photodetectors using small-molecule p-type ZnPc and n-type C60 by tuning the resonant cavity thickness of the photoconductive layer. [5] Yoon et al. reported blue-selective OPDs using a novel polymer donor and PC 60 BM that were fabricated via a simple bulk heterojunction solution process. [6] These successful reports on the development of wavelength-selective OPDs were exclusively achieved by using a photoconductive layer composed of all small molecules, polymer donor/small molecule acceptors or single polymer; [7] polymer/polymer blends have been rarely studied for wavelength-selective OPDs. All-polymer photodetecting layers have the unique advantages of strong absorption coefficients, easy color tunability, solution processability, and especially strong mechanical properties owing to their strongly entangled nanomorphology. [8] However, their relatively disordered backbone structures compared to small molecules broaden their absorption spectra, and thus the blending of polymer donor and polymer acceptor is regarded to be a challenging issue for the realization of narrowwavelength OPDs. In this study, we suggest a new strategy for the development of p-and n-type polymers in order to achieve G-selective all-polymer OPDs while obtaining a low dark current density (J D). Both the polymer donor and acceptor were designed to have a similar G absorption wavelength. Importantly and in addition, we controlled the molar absorption coefficients of both polymers to achieve the desired wavelength selectivity in the OPDs. The absorbance of the polymer donor was maximized by increasing backbone planarity and degree of polymerization, whereas the absorbance of the polymer acceptor was minimized by breaking the π-conjugation via the inclusion of insulating alkyl chains within the conjugated polymers. The significant difference in molar absorption coefficients resulted in G selectivity in the p-n junction photoconductive layer, while the introduced alkyl chains in the main chains effectively suppressed the leakage current in OPDs. The low J D and G selectivity are highly advantageous to detect weak G light signals. Currently available wavelength-selective p-n junction organic photodetectors (OPDs) nearly exclusively use small molecules. In this study, green (G) selective all-polymer p-n junction OPDs are developed by engineering the π-conjugation networks and insulating properties of p-and n-type polymers. Enhanced intermolecular ordering of p-n junction blend films compared to pristine polymer films results in superior hole/electron mobilities and low bimolecular recombination in the devices. Notably, similar G absorption ranges and the huge difference in their absorption coefficients between p-and n-type polymers make excellent G selectivity in the p-n junction OPDs. Thus,...
A perfluorinated and alkylthiolated benzodithiophene (BDT)‐ttTPD‐based donor polymer (P2FS‐ttTPD) was synthesized via a Stille polymerization, and found to have a number average molecular weight (Mn) of 13,000 g/mol (Đ = 2.3). P2FS‐ttTPD has a wide bandgap (1.96 eV) and a deep highest occupied molecular orbital (HOMO) level (−5.70 eV). The perfluorination and alkylthiolation of the polymer backbone lower the polymer's HOMO level significantly. The hole and electron mobilities of P2FS‐ttTPD were determined to be 1.12 × 10−4 and 9.38 × 10−7 cm2/V s, respectively. Polymer solar cell devices prepared with a P2FS‐ttTPD:IT‐4F (1:1) blend as the active layer were found to exhibit power conversion efficiencies of 4.15%, a short‐circuit current density (JSC) of 10.29 mA/cm2, an open‐circuit voltage (VOC) of 0.97 V, and a fill factor of 41.6%. The (1:1) blend devices were found to exhibit high VOC and low Eloss values.
We report an unprecedented but useful functionality of perfluoroarenes to enable exciton scissoring in photomultiplication‐type organic photodiodes (PM‐OPDs). Perfluoroarenes that are covalently connected to polymer donors via photochemical reaction enable us to demonstrate high external quantum efficiency and B‐/G‐/R‐selective PM‐OPDs without the use of conventional acceptor molecules. We investigated the operation mechanism of the suggested perfluoroarene‐driven PM‐OPDs, “How can covalently bonded polymer donor:perfluoroarene PM‐OPDs perform as effectively as polymer donor:fullerene blend‐based PM‐OPDs?”. By employing a series of arenes and conducting steady‐state/time‐resolved photoluminescence and transient absorption spectroscopy analyses, we find that interfacial band bending between the perfluoroaryl group and polymer donor is responsible for exciton scissoring and subsequent electron trapping, which induces photomultiplication. Owing to the acceptor‐free and covalently interconnected photoactive layer in the suggested PM‐OPDs, superior operational and thermal stabilities were observed. Finally, we demonstrated finely patterned B‐/G‐/R‐selective PM‐OPD arrays that enable the construction of highly sensitive passive matrix‐type organic image sensors.This article is protected by copyright. All rights reserved
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