Synthesis of ITIC Derivatives with Extended π-Conjugation as Non-Fullerene Acceptors for Organic Solar Cells

Abstract

The realization of printed organic solar cells (OSCs) as a commercial technology is dependent on the development of high-performance photovoltaic materials suitable for large-scale device manufacture. In this study, the design, synthesis, and characterization of a series of A-D-A′-D-A-type molecular acceptors based on indacenodithienothiophene (IDTT) and thiophene-flanked 2,1,3-benzothiadiazole (DTBT) are reported. The synthesized molecular acceptors showed broader absorption ranges and narrower band gap energies than those of well-known 3,9-bis­(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis­(4-hexylphenyl)-dithieno [2,3-d:2′,3′-d′]-s-indaceno­[1,2-b:5,6-b′]­dithiophene (ITIC)-based molecular acceptors. Furthermore, the synthesized acceptors could tune the frontier molecular orbital energy levels, dipole moments, and their crystallinities by introducing fluorine (F) atoms and cyano (CN) groups on DTBT as a core A′ unit. The cyano-substituted DTBT-based molecular acceptor (CNDTBT-IDTT-FINCN) showed a strong molar absorptivity and dipole moment, high hole/electron charge mobilities, and a favorable face-on orientation using films blended with poly­[(2,6-(4,8-bis­(5-(2-ethylhexyl)­thiophen-2-yl)-benzo­[1,2-b:4,5-b′]­dithiophene))-alt-(5,5-(1′,3′-di-2-thienyl-5′,7′-bis­(2-ethylhexyl)­benzo­[1′,2′-c:4′,5′-c′]­dithiophene-4,8-dione)] (PBDB-T). An inverted organic photovoltaic (OPV) device using CNDTBT-IDTT-FINCN exhibits a power conversion efficiency (PCE) of 9.13% when using PBDB-T as a donor material in small cells (0.12 cm2). Sub-module devices with an active area of 55.45 cm2 are fabricated using bar-coating and exhibit PCEs of up to 7.50%. This demonstration of a high-efficiency large-area device makes CNDTBT-IDTT-FINCN a suitable and promising candidate for printed OPV devices.

p-Tetrafluorophenylene Divinylene-Bridged Nonfullerene Acceptors as Binary Components or Additives for High-Efficiency Organic Solar Cells

“…Relatively higher absorptions from 400 to 650 nm are observed by addition of 1% FB-2IDTT-4Cl . The molar absorptivity, 2.29 × 10 5 M cm –1 , of FB-2IDTT-4Cl was comparable to that of CNDTBT-IDTT-FINCN (Table ); however, it was larger than those of IT-M (1.30 × 10 5 M cm –1 ) and 3,9-bis­(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis­(4-hexylphenyl)-dithieno­[2,3- d :2′,3′- d ′]- s -indaceno­[1,2- b :5,6- b ′]­dithiophene ( ITIC , 1.31 × 10 5 M cm –1 ) and 2,2′-((2 Z ,2′ Z )-((12,13-bis­(2-ethylhexyl)-3,9-diundecyl-12,13-dihydro-[1,2,5]­thiadiazolo­[3,4- e ]­thieno­[2″,3′:4′,5′]­thieno­[2′,3′:4,5] pyrrolo­[3,2- g ]­thieno­[2′,3′:4,5]­thieno­[3,2- b ]­indole-2,10-diyl)­bis­(methanylylidene))­bis­(5,6-difluoro-3-oxo-2,3-dihydro-1 H -indene-2,1-diylidene))­dimalononitrile ( Y6 , 1.07 × 10 5 M cm –1 ) by approximately twofold, respectively.…”

“…We also fabricated inverted OPV devices in which the active layer contained poly­[(2,6-(4,8-bis­(5-(2-ethylhexyl)­thiophen-2-yl)-benzo­[1,2- b :4,5- b ′]-dithiophene))- alt -(5,5-(1′,3′-di-2-thienyl-5′,7′-bis­(2-ethylhexyl)­benzo­[1′,2′- c :4′,5′- c ′]­dithiophene-4,8-dione)] ( PBDB-T ) as the donor and FB-2IDTT-4Cl as the acceptor; the PCE of these devices was as high as 11.4% compared with that of devices fabricated using 3,9-bis­(2-methylene-((3-(1,1-dicyanomethylene)-6/7-methyl)-indanone))-5,5,11,11-tetrakis­(4-hexylphenyl)-dithieno­[2,3- d :2′,3′- d ′]- s -indaceno­[1,2- b :5,6- b ′]­dithiophene IT-M (Figure ) as the reference standard. Furthermore, the PCE of the fabricated devices was higher than that of a device using ITIC-4Cl (PCE 9.1% ± 0.5%) or the cyano-substituted thiophene-flanked benzothiadiazole ( CN )-bridged acceptor CNDTBT-IDTT-FINCN (PCE = 9.13%) . This improvement in PCE can be ascribed to the relatively balanced carrier mobility of the active layer and improved morphology with compatible donors and acceptors that formed the grain size.…”

“…Organic photovoltaic (OPV) devices possess more advantageous features and potential than do inorganic solar cells in terms of their lighter weight, semitransparency, and ability to be fabricated through printing on flexible carriers. − The evolution of nonfullerene acceptors as n-type materials has progressively advanced the development and applicability of OPV devices. − Furthermore, the modification of nonfullerene acceptors with fused-ring electron acceptors through electronic effects can improve the power conversion efficiency (PCE) of devices; , specifically, the PCE of OPV devices has been increased to 17–18% using modification techniques involving the displacement of the core structure of fused-ring aromatics, modification of soluble side chains, and incorporation of electron-poor end groups. − The modification engineering of such fused-ring aromatics aims at creating near-infrared absorption, , which relies on the extension of the number of fused rings, − unidirectional extension of fused rings, varying constitutional isomers of the core structure, , and linearity of the core . The number of fused-ring units could alter the optical and electrochemical properties of the molecule acceptors; accordingly, the PCE can be improved through the engineering of fused-ring units. − …”

Perovskite Quantum Dot Solar Cells: An Overview of the Current Advances and Future Perspectives

“…These substances are conjugated molecules, already established as excellent p‐ or n‐type organic semiconductors. [ 130–139 ] They do not only contribute by protecting the PQDs’ surfaces and, sometimes, for surface passivation, [ 51 ] but also play a role in the charge extraction due to their semiconducting properties. Improved PCEs are obtained as a consequence.…”

Design and Synthesis of Annulated Benzothiadiazoles via Dithiolate Formation for Ambipolar Organic Semiconductors

“…The most common substitutions are through heteroannulation 22,23 as in [1,2,5]thiadiazolo [3,4-g]quinoxaline (TDQ), 24,25 benzo[1,2-c:4,5-c']bis [1,2,5]thiadiazole (BBT), 21,26 and benzo(triazole-thiadiazole) (BTzTD), 27,28 or attachment of electron withdrawing fluorides as in difluoro-substituted BTD (ffBTD) [29][30][31][32][33][34][35][36][37][38] and dicyano-substituted BTD. [39][40][41] For these annulated TDQ and BBT systems, while annulation effectively lowers the LUMO energy to give stronger electron acceptors, it simultaneously raises the HOMO energies, which is disadvantageous for their incorporation in electron donor materials for OPVs as it is correlated to a decrease of open-circuit voltage. 22 Herein we devised a new 5,6-annulated BTD ring system using aromatic nucleophilic substitution (S N Ar) to introduce an electron withdrawing 2-(1,3-dithiol-2-ylidene)malonitrile group using the common ffBTD as a precursor.…”