An Easily Accessible Donor−π-Acceptor-Conjugated Small Molecule from a 4,8-Dialkoxybenzo[1,2-b:4,5-b′]dithiophene Unit for Efficient Solution-Processed Organic Solar Cells

Abstract

A new donor-acceptor-conjugated organic small molecule, BDT(TBT)(2), comprised of benzo[1,2-b:4,5-b']dithiophene and 2,1,3-benzothiadiazole units was designed and synthesized. The small molecule BDT(TBT)(2) in its thin film showed an absorption band in the range of 300-700 nm with an absorption edge at 650 nm and an optical band gap of 1.90 eV. As estimated from the cyclic voltammetry measurements, the HOMO and LUMO energy levels of BDT(TBT)(2) were -5.44 and -3.37 eV, respectively. The spin-coated thin film of BDT(TBT)(2) exhibited p-channel output characteristics with a hole mobility of 2.7 × 10(-6). BDT(TBT)(2), when explored as an electron-donor material in solution-processed bulk-heterojunction organic solar cells in conjunction with a PC(71)BM acceptor with an active layer thickness of 50-55 nm, generated a power conversion efficiency (PCE) of 1.18%. A more impressive PCE of ~2.9% with a short-circuit current density (J(sc)) of 7.94 mA cm(-2) and an open-circuit voltage (V(oc)) of 0.89 V was achieved when the active layer of the cell was annealed at higher temperature (~180 °C).

A Solution‐Processable Small Molecule Based on Benzodithiophene and Diketopyrrolopyrrole for High‐Performance Organic Solar Cells

“…In general, polymers based on 5‐alkylthiophene‐2‐yl‐substituted BDT unit exhibit improved photovoltaic properties relative to their alkoxy‐substituted BDT analogues 32. BDT unit has also been used in several linear small molecules for OPVs 16, 19, 33. OPVs based on blends of alkoxy‐substituted BDT small molecule donors and PC 71 BM acceptor showed the best PCE of 7.38% 19.…”

Phenyl‐1,3,5‐Trithienyl‐Diketopyrrolopyrrole: A Molecular Backbone Potentially Affording High Efficiency for Solution‐Processed Small‐Molecule Organic Solar Cells through Judicious Molecular Design

“…As such, to shed light on the 1,3,5-substituted phenyl core, herein we utilize the 1,3,5-substituted phenyl as an electron-donor core, the widely reported unit of diketopyrrolopyrrole (DPP) [28][29][30][31][32][33] as the electron-acceptor unit, and thiophene and two-dimensional benzodithiophene (2D-BDT) [24,25,31,44,45] as alternative units to adjust the molecular configuration and conjugation, thereby obtaining a series of C 3 -or C 2 -symmetric molecules, as shown in Scheme 1. As such, to shed light on the 1,3,5-substituted phenyl core, herein we utilize the 1,3,5-substituted phenyl as an electron-donor core, the widely reported unit of diketopyrrolopyrrole (DPP) [28][29][30][31][32][33] as the electron-acceptor unit, and thiophene and two-dimensional benzodithiophene (2D-BDT) [24,25,31,44,45] as alternative units to adjust the molecular configuration and conjugation, thereby obtaining a series of C 3 -or C 2 -symmetric molecules, as shown in Scheme 1.…”

“…The efficiency of SM-OSCs is deeply related to their light-harvesting ability, exciton diffusion, exciton separation efficiency, and carrier transporting ability, all of which can be adjusted by the molecular structures and device optimization. As such, to shed light on the 1,3,5-substituted phenyl core, herein we utilize the 1,3,5-substituted phenyl as an electron-donor core, the widely reported unit of diketopyrrolopyrrole (DPP) [28][29][30][31][32][33] as the electron-acceptor unit, and thiophene and two-dimensional benzodithiophene (2D-BDT) [24,25,31,44,45] as alternative units to adjust the molecular configuration and conjugation, thereby obtaining a series of C 3 -or C 2 -symmetric molecules, as shown in Scheme 1. Firstly, we selected the phenyl-1,3,5-trithienyl (3T-P) core to covalently bridge three-armed diketopyrrolopyrrole (DPP) units, thus forming a C 3 -symmetric conjugated phenyl-1,3,5trithienyl-DPP backbone (3D-T-P).…”

Benzothiadiazole‐Based Small‐Molecule Semiconductors for Organic Thin‐Film Transistors and Complementary‐like Inverters

“…[2] Recently,t he strategy of designing moleculars tructures with electron-accepting ande lectrondonating moieties in one unit has gained considerable interest for organic semiconducting materials with high electrical performance. [3] With ad onor-acceptor (D-A) design,t he highest occupied molecular orbital (HOMO) andl owestu noccupied molecular orbital( LUMO) energies of organic semiconductors can be tuned to improve charge transport of both holes and electrons through p-conjugated backbones. [4] Despite recent achievements, novel solution-processable compounds with high electrical performance are still in demand for aw ider range of applications.…”