Molecular Engineering of a Donor–Acceptor Polymer To Realize Single Band Absorption toward a Red-Selective Thin-Film Organic Photodiode

Abstract

Herein, we explore the strategy of realizing a red-selective thin-film organic photodiode (OPD) by synthesizing a new copolymer with a highly selective red-absorption feature. PCZ-Th-DPP, with phenanthrocarbazole (PCZ) and diketopyrrolopyrrole (DPP) as donor and acceptor units, respectively, was strategically designed/synthesized based on a time-dependent density functional theory calculation, which predicted the significant suppression of the band II absorption of PCZ-Th-DPP due to the extremely efficient intramolecular charge transfer. We demonstrate that the synthesized PCZ-Th-DPP exhibits not only a high absorption coefficient within the red-selective band I region, as theoretically predicted, but also a preferential face-on intermolecular structure in the thin-film state, which is beneficial for vertical charge extraction as an outcome of a glancing incidence X-ray diffraction study. By employing PCZ-Th-DPP as a photoactive layer of Schottky OPD, to fully match its absorption characteristic to the spectral response of the red-selective OPD, we demonstrate a genuine red-selective specific detectivity in the order of 1012 Jones while maintaining a thin active layer thickness of ∼300 nm. This work demonstrates the possibility of realizing a full color image sensor with a synthetic approach to the constituting active layers without optical manipulation.

Direct Observation of Confinement Effects of Semiconducting Polymers in Polymer Blend Electronic Systems

“…On the basis of these results, it can be speculated that DPP2T, 29‐DPP, and PCDTPT can additionally develop a strong polar intermolecular interaction, when compared to P3HT (homopolymer) and P18 (D‐D copolymer), because they possess relatively large dipole moments in the polymer backbone with a polarity difference between the donor–acceptor (D–A) units. [ 45 , 46 , 47 , 48 , 49 ] In addition, to identify the aggregation strength of the SPs, we checked their UV–vis absorption spectra considering both the solution and film states. As shown in Figure 1b , P18, DPP2T, 29‐DPP, and PCDTPT polymers demonstrated almost negligible bathochromic shifts of absorption peaks between solutions and films, which implies that P18, DPP2T, 29‐DPP, and PCDTPT polymers undergo pre‐aggregation even in their solution states with strong intermolecular interactions, whereas the absorption peak of the P3HT solution (≈456 nm) drastically shifted to 555 nm in the film state.…”

Strengthening the Intrachain Interconnection of Polymers by the Naphthalene Diimide–Pyrene Complementary Interactions

“…In the nomenclature, N , L , and A denote NDI, linear pyrene, and angular pyrene. The computational results indicate that the intramolecular charge transfer (ICT) , from bithiophenes to NDIs is the dominant contribution in the absorption at ≈1.55 eV, and the absorption band at ≈3.20 eV mainly comes from π–π* transitions (Figure S6, Supporting Information). Moreover, additional π–π* transitions of pyrene coupling with bithiophene functionality are estimated theoretically.…”

Organic Thin-Film Red-Light Photodiodes with Tunable Spectral Response Via Selective Exciton Activation

“…As a result, better absorption of the incident light allows significant reduction of active layer thickness (as low as hundreds of nanometers), which is essential for preventing crosstalk between pixels . In addition, the absorption spectrum of organic semiconductors can be controlled by molecular design, which makes multicolor imaging without color filters feasible . Furthermore, like all other types of organic devices, OPDs enable solution-deposition methods and are compatible with flexible substrates without sacrificing the high optoelectronic properties and mechanical robustness.…”

“…9 In addition, the absorption spectrum of organic semiconductors can be controlled by molecular design, which makes multicolor imaging without color filters feasible. 10 Furthermore, like all other types of organic devices, OPDs enable solutiondeposition methods and are compatible with flexible substrates without sacrificing the high optoelectronic properties and mechanical robustness.…”