Synthesis, Molecular and Photovoltaic Properties of an Indolo[3,2‐b]indole‐Based Acceptor–Donor–Acceptor Small Molecule

Abstract

Indolo[3,2‐b]indole, containing two fused indole units, is an unexplored but promising electron‐rich molecule for constructing donor–acceptor materials due to its planar, symmetric, and extended conjugated structure. We have successfully developed a new synthetic pathway to prepare 2,7‐diboronic ester‐indolo[3,2‐b]indole, which was then reacted with dithienodiketopyrrolo‐pyrrole acceptor to afford a new acceptor–donor–acceptor (A–D–A) conjugated molecule, 2,7‐bis(dithienodiketopyrrolo‐pyrrole)indolo[3,2‐b]indole (2,7‐DPPIIDPP). II is used to stand for indolo[3,2‐b]indole in order to emphasize that this compound is constructed from two indole units. The A–D–A linkage through the 2,7‐positions of II not only preserves the phenylene units in the para‐conjugation but also renders stronger electron‐donating strength. This material exhibited good thermal stability, high crystallinity, and broad UV/Vis absorption. The solution‐processed bulk heterojunction device using the configuration of ITO/PEDOT:PSS/2,7‐DPPIIDPP:PC71BM/Ca/Al exhibited a Voc of 0.72 V, a Jsc of 6.88 mA/cm2, and an FF of 49.6 %, leading to a power conversion efficiency (PCE) of 2.45 %.

A new V-shaped triphenylamine/diketopyrrolopyrrole containing donor material for small molecule organic solar cells

“…For example, solution-processed small-molecule OSCs based on BDT-2DPP with two-dimensional conjugated benzodithiophene (BDT) as the donating core and DPP as the accepting arm exhibited PCE over 5.3%. 38,39 The calculated LUMO and HOMO energy levels are 2.65 and 4.58 eV, respectively, which are in good agreement with other TPA/DPP derivatives. 30-33 Therefore, there is still great room for designing new materials based on TPA/DPP for high performance organic solar cells.…”

Design, Synthesis, and Versatile Processing of Indolo[3,2‐b]indole‐Based π‐Conjugated Molecules for High‐Performance Organic Field‐Effect Transistors

“…Although synthesis route to 2,7-dibromo-5,10-dihydro-IDID was previously reported by Cheng group (seven steps with 4.5% overall yield), [ 23 ] we could develop our own route for the effi cient core synthesis, on the basis of selective reactivity of Sonogashira coupling reaction (six steps with 20.7% overall yield, Scheme S1, Supporting Information). 2,7-dibromo-N,N -dihexyl-IDID as a common intermediate compound was synthesized by alkylation of 2,7-dibromo-5,10-dihydro-IDID (compound 7 in Scheme S1, Supporting Information ) .…”

“…IDID thus allows symmetrical structural derivatization in ( N , N -), (2,7-), and (3,8-) positions affording diverse opportunities to control their π-conjugation and solubility with higher fl exibility than the case of pentacene and heptacene analogues (e.g., indolocarbazole, and heptazole). [23][24][25] In case of OFET application, only one report of vacuum-deposited (VD) device was made using underivatized IDID core which showed rather low mobility value of ≈1.0 × 10 −3 cm 2 V −1 s −1 ; [ 25 ] we thus believe it is worthwhile to tailor molecular structures of IDID with an aim to realize high-performance and versatilely processable organic semiconductors via precise comprehension of structure-property relationship. [23][24][25] In case of OFET application, only one report of vacuum-deposited (VD) device was made using underivatized IDID core which showed rather low mobility value of ≈1.0 × 10 −3 cm 2 V −1 s −1 ; [ 25 ] we thus believe it is worthwhile to tailor molecular structures of IDID with an aim to realize high-performance and versatilely processable organic semiconductors via precise comprehension of structure-property relationship.…”

Indolo[3,2-b]indole-based crystalline hole-transporting material for highly efficient perovskite solar cells

“…Among various types of pyrrole-containing heteroacene, attempts have been made to exploit indolo[3,2- b ]indole (IDID)-based π-conjugated p-type semiconductors in organic light-emitting diodes (OLED), organic field-effect transistors (OFET), and organic photovoltaics (OPV). 6 Very recently, we demonstrated the high potential of IDID as a p-type backbone unit with its well-designed molecular structure (see Fig. 1b ), exhibiting an outstanding field-effect hole mobility of 0.97 cm 2 V –1 s –1 in a vacuum-deposited (VD) crystalline film, and versatile processability.…”