Site-selective synthesis and characterization of BODIPY-acetylene copolymers and their transistor properties

Abstract

To study the effect of site-selective copolymerization of borondipyrromethene (BODIPY) with acetylene on the structural and optoelectronic properties, three copolymers P1-P3 were synthesized by the Sonogashira cross-coupling of BODIPY units with diacetylene and bromine capping through all the possible linkages: a-a (P1), a-b (P2), and b-b (P3). The optoelectronic properties of the polymers were investigated systematically to understand the effect of site-selective polymerization. The HOMO levels of the polymers were significantly tuned from P1 to P3 with negligible change in the LUMO levels. Broadening of absorption spectra from P3 to P1 was observed because of increase in the extent of conjugation.Additionally, the charge transport properties of these polymers in organic thin-film transistors (OTFTs) revealed that P1 and P3 exhibited only p-type mobility, whereas P2 exhibited electron mobility. Notably, the further investigations of the surface morphology of polymer films by atomic force microscopy (AFM) unveiled that comb like nanostructural arrangements in P3 was beneficial for the charge-carrier mobility over the circular arrangements in P1 and P2.

BODIPY‐Based Semiconducting Materials for Organic Bulk Heterojunction Photovoltaics and Thin‐Film Transistors

“…The poor electrical performance of P22 originated from the backbone curvature in the polymer chain in every monomeric unit, which has a direct effect on thin‐film morphology and device performance. This study was the first example of band‐gap engineering for BODIPY‐acetylene polymeric semiconductors …”

“…Debnath and his colleagues synthesized three novel BODIPY-acetylene copolymers P22-P24 using different substitution positions on the BODIPY core ( Figure 16). [126] Site selective polymerization enabled band gap engineering within these copolymers. From P22 to P24, the HOMO energy level significantly changed, while the LUMO level remained very similar.…”

“…This study was the first example of band-gap engineering for BODIPY-acetylene polymeric semiconductors. [126] In addition to the photovoltaic studies with copolymer P2 (Figure 8), Usta et al also investigated its OTFT characteristics. The transistor device was fabricated by spin coating copolymer solution on a PS-brush treated substrate, which exhibited a hole mobility of 5 × 10 À 3 cm 2 V À 1 s À 1 .…”

“…Debnath and his colleagues synthesized three novel BODIPY‐acetylene copolymers P22 – P24 using different substitution positions on the BODIPY core (Figure ) . Site selective polymerization enabled band gap engineering within these copolymers.…”

Architectures and Applications of BODIPY-Based Conjugated Polymers

“…Except for charge mobility, the BODIPYs with connectivity at α-position may produce better photovoltaic properties [29] and more intriguing nonlinear optical properties [32]. [30]. Copyright @ 2016, John Wiley and Sons.…”