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

Abstract

The rapid emergence of organic (opto)electronics as a promising alternative to conventional (opto)electronics has been achieved through the design and development of novel π‐conjugated systems. Among various semiconducting structural platforms, 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene (BODIPY) π‐systems have recently attracted attention for use in organic thin‐films transistors (OTFTs) and organic photovoltaics (OPVs). This Review article provides an overview of the developments in the past 10 years on the structural design and synthesis of BODIPY‐based organic semiconductors and their application in OTFT/OPV devices. The findings summarized and discussed here include the most recent breakthroughs in BODIPYs with record‐high charge carrier mobilities and power conversion efficiencies (PCEs). The most up‐to‐date design rationales and discussions providing a strong understanding of structure‐property‐function relationships in BODIPY‐based semiconductors are presented. Thus, this review is expected to inspire new research for future materials developments/applications in this family of molecules.

A Solution‐Processable meso‐Phenyl‐BODIPY‐Based n‐Channel Semiconductor with Enhanced Fluorescence Emission

“…OFETs demonstrated typical n ‐channel transistor characteristics under vacuum with appreciable electron mobility of 0.0054 cm 2 /V ⋅ s and I on /I off ratio of 3.7×10 4 (Figures A and B), which correlate well with BDY‐Ph‐2T‐Ph‐BDY's computed/measured electronic structure and the observed solid‐state microstructure/morphology. The semiconducting performance of BDY‐Ph‐2T‐Ph‐BDY is among the highest of previously reported n ‐channel BODIPY semiconductors (μ e ∼10 −4 –0.01 cm 2 /V ⋅ s) . The small decrease in electron mobility, as compared with the best results of BDY‐4T‐BDY (μ e =0.01 cm 2 /V ⋅ s), could be attributed to increased LUMO energy level, narrower π‐delocalization, and increased D‐A backbone twist in the new molecular structure.…”

“…In addition to their promising charge‐transport and photophysical properties, the most favorable physical and chemical properties of π‐conjugated small molecules are structural versatility, ease of synthesis‐purification and fabrication, and synthetic (batch‐to‐batch) reproducibility . Among various π‐building blocks, 4,4‐difluoro‐4‐bora‐ 3a,4a ‐diaza‐ s ‐indacene (BODIPY) has recently attracted attention in the design of molecular semiconductors for optoelectronics . In the past few decades, BODIPY‐based small molecules have been studied as fluorescent switches/sensors, chemosensors, biochemical labels, and photodynamic therapy agents, and they have shown remarkable photophysical properties such as high fluorescence quantum yield, large extinction coefficient, small Stokes shifts, high photostability, and tunable absorption/fluorescence profiles .…”

Synthesis and Properties of Azadipyrromethene‐Based Complexes with Nitrile Substitution

“…While the unfavorable film morphologies of P3HT:Zn(L1) 2 and P3HT:Zn(L2) 2 blend films can explain their low OPV performance, further experiments are needed to confirm. For example, future design of solution processable nitrile‐based ADP chelates will include using alkyl solubilizing groups,[4b], as alkyl solubilizing groups have been shown to facilitate solution processing as well as improve device properties of organic semiconductors …”

Synthesis and Functions of Oligomeric and Multidentate Dipyrrin Derivatives and their Complexes

“…The dipyrrin (dipyrromethene) boron complex 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) has recently attracted considerable attention due to its narrow and intense absorption and emission, [1][2][3][4] although the first dipyrrins as a bidentate ligand with the two nitrogen atoms (N 2 dipyrrins in this Account) and the BODIPYs were reported by Treibs and Kreuzer in 1968. 5 The excellent photophysical properties of BODIPY derivatives have been utilized for fluorescence tag and probe molecules, [6][7][8][9][10][11][12] fluorescence sensors, 8,[10][11][12][13][14] bioimaging, 9,11,12,15,16 electrogenerated chemiluminescence dye, 17 and possible applications such as organic thin-film transistors, 18 laser dye, 19 OLED (organic lightemitting diode), 17,[20][21][22][23] photodynamic therapy, [24][25][26] solar cells, 19,[27][28][29] polymer photonics devices, 30 etc. There are many reports concerning the derivatization of the N 2bidentate dipyrrins by attaching a variety of substituents, extending the -planar dipyrrin nucleus, and introducing a nitrogen atom into the dipyrrin framework, then preparing the corresponding boron complexes.…”