Developing High‐Performance Electron‐Rich Unit End‐Capped Wide Bandgap Oligomeric Donor by Weak Electron‐Deficient Central Core Strategy

Abstract

Here, we report the synthesis of a pair of end-capped hexafluorinated oligomeric donors with electron-rich unit for fullerene-based organic solar cells, named as BTZ6F and BTA6F, which include the same difluorobenzothiadiazoles as internal electron-deficient unit, but differ in distinct electrondeficient central core, respectively. BTA6F with difluorobenzotriazoles as weak electron-deficient central core, shows slightly wider bandgap, higher hole mobility, more ordered and crystalline blend film, and better device performances in term of higher PCE, J sc , and FF. Moreover, the PCEs and fill factors show damatically increase upon SVA or a combined TA and SVA treatment, which can be ascribed to an optimal morphology with highly crystalline content and clearly nanoscale phase separation as revealed by morphology characterization. As a result, the devices from BTA6F exhibit a PCE of 9.04%, which is the best organic solar cell based on difluorobenzotriazoles cored oligomers as a donor reported to date. Equally important, the obtained wide bandgap oligomer BTA6F is among one of the few electronrich unit end-capped oligomeric donor that can deliver high PCE of 9%. These results highlight the weak difluorinated electron-deficient central core strategy as a promising approach to further improve the photovoltaic performance of electron-rich unit end-capped oligomers.

Branched 2‐Ethylhexyl Substituted Indacenodithieno[3,2‐b]Thiophene Core Enabling Wide‐Bandgap Small Molecule for Fullerene‐Based Organic Solar Cells with 9.15% Efficiency: Effect of Length and Position of Fused Polycyclic Aromatic Units

“…A slow drop of n ‐BuLi into a solution of EH‐IDTT , and followed by addition of trimethyltin chloride produced the ditin reagent 7 as light‐yellow oil. The end‐capped unit 9 was obtained by reaction of Compound 8 with 4,7‐dibromo‐5,6‐difluorobenzo[c][1,2,5]thiadiazole through Stille coupling reaction using Pd 2 (dba) 3 /P( o ‐tol) 3 as catalyst. Finally, TT4FIDTT and DT4FIDTT were obtained through a twofolds Stille coupling reaction between ditin 7 and 9 or 10 using Pd 2 (dba) 3 /P( o ‐tol) 3 as catalyst with isolated yield of 80% and 65%, respectively .…”

One‐Pot Synthesis of 3‐ to 15‐Mer π‐Conjugated Discrete Oligomers with Widely Tunable Optical Properties

“…Monodisperse conjugated oligomers (MCOs) ( Đ = 1.0) with defined structures have been extensively studied to unravel the inherent chain‐length‐dependent properties for optoelectronic device applications. [ 2‐11 ] The π‐conjugated materials with high‐lying highest occupied molecular orbital (HOMO) containing exclusively electron‐donating (D) building blocks are a kind of ideal materials for hole transporting layers in organic electronic devices, such as organic light emitting diodes (OLEDs) [ 11‐14 ] and perovskite solar cells (PSCs), [ 15 ] etc . The previously reported all‐D long‐chain MCOs were mainly focused on ones that are made up of single electron‐ donating moieties, such as oligo‐phenylene, [ 16 ] ‐thiophene [ 17‐19 ] and ‐fluorene, [ 20 ] etc ., synthesized by Kumada, Suzuki or Stille C—M/C—Br (M = Mg, B and Sn) cross couplings.…”

Organic solar cells: Current perspectives on graphene‐based materials for electrodes, electron acceptors and interfacial layers

“…The conducting electrodes also collect and transport the photo‐generated carriers to the external circuit. On the other hand, the active layer consists of randomly dispersed organic or inorganic nanostructured electron acceptors within a conjugated host donor matrix, which can either be a polymer, 35,36 small molecule, 37,38 oligomer 39,40 or dendrimer 41,42 . The donor‐acceptor interfaces form BHJs that act as sites for exciton dissociation and bi‐continuous nanoscale networks for carrier transport to the electrodes 43 .…”