Highly Sensitive Thin-Film Field-Effect Transistor Sensor for Ammonia with the DPP-Bithiophene Conjugated Polymer Entailing Thermally Cleavable <i>tert</i>-Butoxy Groups in the Side Chains

The sensing and detection of ammonia have received increasing attention in recent years because of the growing emphasis on environmental and health issues. In this paper, we report a thin-film field-effect transistor (FET)-based sensor for ammonia and other amines with remarkable high sensitivity and satisfactory selectivity by employing the DPP-bithiophene conjugated polymer pDPPBu-BT in which <i>tert</i>-butoxycarboxyl groups are incorporated in the side chains. This polymer thin film shows <i>p</i>-type semiconducting property. On the basis of TGA and FT-IR analysis, <i>tert</i>-butoxycarboxyl groups can be transformed into the −COOH ones by eliminating gaseous isobutylene after thermal annealing of pDPPBu-BT thin film at 240 °C. The FET with the thermally treated thin film of pDPPBu-BT displays remarkably sensitive and selective response toward ammonia and volatile amines. This can be attributed to the fact that the elimination of gaseous isobutylene accompanies the formation of nanopores with the thin film, which will facilitate the diffusion and interaction of ammonia and other amines with the semiconducting layer, leading to high sensitivity and fast response for this FET sensor. This FET sensor can detect ammonia down to 10 ppb and the interferences from other volatile analytes except amines can be negligible

Alternating Conjugated Electron Donor–Acceptor Polymers Entailing Pechmann Dye Framework as the Electron Acceptor Moieties for High Performance Organic Semiconductors with Tunable Characteristics

In this paper, we report the design, synthesis and semiconducting behavior of two conjugated D–A polymers <b>P-BPDTT</b> and <b>P-BPDBT</b> which entail <b>BPD</b>, a Pechmann dye framework, as electron accepting moieties, and thieno­[3,2-<i>b</i>]­thiophene and 2,2′-bithiophene as electron donating moieties. Their HOMO/LUMO energies and bandgaps were estimated based on the respective cyclic voltammgrams and absorption spectra of thin films. <b>P-BPDTT</b> possesses lower LUMO level and narrower bandgap than <b>P-BPDBT</b>. On the basis of the characterization of the field-effect transistors, a thin film of <b>P-BPDTT</b> exhibits ambipolar semiconducting properties with hole and electron mobilities reaching 1.24 cm² V^–1 s^–1 and 0.82 cm² V^–1 s^–1, respectively, after thermal annealing. In comparison, thin film of <b>P-BPDBT</b> only shows <i>p</i>-type semiconducting behavior with hole mobility up to 1.37 cm² V^–1 s^–1. AFM and XRD studies were presented to understand the interchain arrangements on the substrates and the variation of carrier mobilities

New Donor–Acceptor–Donor Molecules with Pechmann Dye as the Core Moiety for Solution-Processed Good-Performance Organic Field-Effect Transistors

In this paper, we report the synthesis and characterization of two new D-A-D molecules (<i>E</i>)-5,5′-bis­(5-(benzo­[<i>b</i>]­thiophen-2-yl)­thiophen-2-yl)-1,1′-bis­(2-ethyl- hexyl)-[3,3′-bipyrrolylidene]-2,2′(1<i>H</i>,1′<i>H</i>)-dione (<b>BTBPD</b>) and (<i>E</i>)-5,5′-bis- (5-(benzo­[<i>b</i>]­furan-2-yl)­thiophen-2-yl)-1,1′-bis­(2-ethylhexyl)-[3,3′-bipyrrolylidene]-2,2′(1<i>H</i>,1′<i>H</i>)-dione (<b>BFBPD</b>). They entail bipyrrolylidene-2,2′(1<i>H</i>,1′<i>H</i>)-dione (<b>BPD</b>, known as Pechmann dye) as the electron-accepting core that is flanked by two benzo­[<i>b</i>]­thiophene moieties and two benzo­[<i>b</i>]­furan moieties, respectively. Crystal structures of <b>BTBPD</b> and <b>BFBPD</b> provide solid evidence for the intermolecular donor–acceptor (D-A) interactions, which are favorable for improving charge transport performance. Organic field-effect transistors (OFETs) were prepared based on thin films of <b>BTBPD</b> and <b>BFBPD</b> through solution-processed technique. OFETs of <b>BTBPD</b> exhibit relatively high hole mobility up to 1.4 cm² V^–1 s^–1 with high on/off ratio up to 10⁶. In comparison, the hole mobility of OFETs with <b>BFBPD</b> (0.14 cm² V^–1 s^–1) is relatively low, because of the poor thin-film morphology and low molecular ordering, even after annealing. Thin-film morphological and XRD studies were carried out to understand the variation of hole mobilities after annealing at different temperatures. The present studies clearly demonstrate the potentials of <b>BPD</b> that is planar and polar as the electron-acceptor moiety to build D-A molecules for organic semiconductors with good performance

New Donor–Acceptor–Donor Molecules with Pechmann Dye as the Core Moiety for Solution-Processed Good-Performance Organic Field-Effect Transistors

In this paper, we report the synthesis and characterization of two new D-A-D molecules (<i>E</i>)-5,5′-bis­(5-(benzo­[<i>b</i>]­thiophen-2-yl)­thiophen-2-yl)-1,1′-bis­(2-ethyl- hexyl)-[3,3′-bipyrrolylidene]-2,2′(1<i>H</i>,1′<i>H</i>)-dione (<b>BTBPD</b>) and (<i>E</i>)-5,5′-bis- (5-(benzo­[<i>b</i>]­furan-2-yl)­thiophen-2-yl)-1,1′-bis­(2-ethylhexyl)-[3,3′-bipyrrolylidene]-2,2′(1<i>H</i>,1′<i>H</i>)-dione (<b>BFBPD</b>). They entail bipyrrolylidene-2,2′(1<i>H</i>,1′<i>H</i>)-dione (<b>BPD</b>, known as Pechmann dye) as the electron-accepting core that is flanked by two benzo­[<i>b</i>]­thiophene moieties and two benzo­[<i>b</i>]­furan moieties, respectively. Crystal structures of <b>BTBPD</b> and <b>BFBPD</b> provide solid evidence for the intermolecular donor–acceptor (D-A) interactions, which are favorable for improving charge transport performance. Organic field-effect transistors (OFETs) were prepared based on thin films of <b>BTBPD</b> and <b>BFBPD</b> through solution-processed technique. OFETs of <b>BTBPD</b> exhibit relatively high hole mobility up to 1.4 cm² V^–1 s^–1 with high on/off ratio up to 10⁶. In comparison, the hole mobility of OFETs with <b>BFBPD</b> (0.14 cm² V^–1 s^–1) is relatively low, because of the poor thin-film morphology and low molecular ordering, even after annealing. Thin-film morphological and XRD studies were carried out to understand the variation of hole mobilities after annealing at different temperatures. The present studies clearly demonstrate the potentials of <b>BPD</b> that is planar and polar as the electron-acceptor moiety to build D-A molecules for organic semiconductors with good performance

Tuning the Semiconducting Behaviors of New Alternating Dithienyldiketopyrrolopyrrole–Azulene Conjugated Polymers by Varying the Linking Positions of Azulene

Three new conjugated polymers <b>DPPA1</b>, <b>DPPA2</b>, and <b>DPPA3</b> with dithienyldiketopyrrolopyrrole (DPP) and azulene moieties were synthesized and characterized. The five-membered rings of azulene are connected with DPP in <b>DPPA1</b> and <b>DPPA2</b>, whereas the seven-membered ring of azulene is incorporated into the backbone of <b>DPPA3</b>. The LUMO energy of <b>DPPA3</b>, which was determined on the basis of the respective cyclic voltammograms and absorption spectra, is lower than those of <b>DPPA1</b> and <b>DPPA2</b>. OFETs were successfully fabricated with thin films of <b>DPPA1</b>, <b>DPPA2</b>, and <b>DPPA3</b>. Thin films of <b>DPPA1</b> and <b>DPPA2</b> exhibit p-type semiconducting properties with hole mobilities up to 0.97 cm² V^–1 s^–1, whereas typical ambipolar behavior is found for thin film of <b>DPPA3</b> with hole and electron mobilities reaching 0.062 cm² V^–1 s^–1 and 0.021 cm² V^–1 s^–1, respectively. The results reveal that semiconducting properties of <b>DPPA1</b>, <b>DPPA2</b>, and <b>DPPA3</b> can be tuned by varying the linkage positions of azulene with DPP moieties. Furthermore, <b>DPPA1</b>, <b>DPPA2</b>, and <b>DPPA3</b> were tested preliminarily as photovoltaic materials. The power conversion efficiency (PCE) reaches 2.04% for the blending thin film <b>DPPA1</b> with PC₇₁BM