Heteroleptic Ruthenium(II) Complexes with 2,2′-Bipyridines Having Carbonitriles as Anchoring Groups for ZnO Surfaces: Syntheses, Physicochemical Properties, and Applications in Organic Solar Cells

Abstract

Heteroleptic ruthenium (II) complexes were used for sensitizing ZnO surfaces in organic solar cells (OSCs) as mediators with photoactive layers. The complexes [Ru(4,4′-X 2 -bpy)(Mebpy-CN) 2 ] 2+ (with X = −CH 3 , −OCH 3 and −N(CH 3 ) 2 ; bpy = 2,2′-bipyridine; Mebpy-CN = 4-methyl-2,2′-bipyridine-4′-carbonitrile) were synthesized and studied by analytical and spectroscopical techniques. Spectroscopic, photophysical, and electrochemical properties were tuned by changing the electron-donating ability of the -X substituents at the 4,4′-positions of the bpy ring and rationalized by quantum mechanical calculations. These complexes were attached through nitrile groups to ZnO as interfacial layer in an OSC device with a PBDB-T:ITIC photoactive layer. This modified inorganic electron transport layer generates enhancement in photoconversion of the solar cells, reaching up to a 23% increase with respect to the unsensitized OSCs. The introduction of these dyes suppresses some degradative reactions of the nonfullerene acceptor due to the photocatalytic activity of zinc oxide, which was maintained stable for about 11 months. Improving OSC efficiencies and stabilities can thus be achieved by a judicious combination of new inorganic and organic materials.

Organic–inorganic hybrid cathode interlayer materials for efficient organic solar cells

“…Ru coordination complex type sensitizers can also modify the ZnO film. 107 What's more, a 2D MOF layer has been used to obtain a hybrid with PEIE, and the MOF-PEIE composite between ZnO and the active layer can significantly improve the conductivity, tune aligned energy levels and thus reduce the charge recombination. 108 Although ZnO-based double layer CILs can afford high PCEs and much improved light stability, the sophisticated processing approach is not so friendly to scale R2R manufacturing, and this kind of CILs have been rarely adopted to fabricate large area and flexible OSCs.…”

Recent Progress in High‐voltage Aqueous Zinc‐based Hybrid Redox Flow Batteries

“…The redox mediator strategy, mainly applied in solar cells and lithium-air batteries, served as an electron shuttle between the electrodes and the reactants for improving the electrochemical performance. [109,110] It could participate in the electrochemical reaction between the solid reactants and the electrodes without any physical contact. In addition, the discharge mediators with redox potential lower than Mn 2 + /MnO 2 redox couple could be applied for reducing the deposited MnO 2 during the discharge process.…”

“…The redox mediator strategy, mainly applied in solar cells and lithium‐air batteries, served as an electron shuttle between the electrodes and the reactants for improving the electrochemical performance [109,110] . It could participate in the electrochemical reaction between the solid reactants and the electrodes without any physical contact.…”

Triplet Homoleptic Iridium(III) Complex as a Potential Donor Material for Organic Solar Cells

“…Bulk-heterojunction (BHJ) organic solar cells (OSCs) have received considerable attention in the past few decades owing to their advantages of solution processing, lightweight, flexibility, large area, etc. 1,2 Recently, due to the ease of chemical modification on organic/polymer materials, wellmatched polymer donors with non-fullerene fused-ring smallmolecular acceptors have broken through the power conversion efficiency (PCE) to 20%. 3,4 In general, the working mechanism of typical BHJ OSCs could be demonstrated as four key steps: light absorption and exciton generation in the photoactive donor and/or acceptor materials, exciton diffusion to the donor/acceptor (D/A) interface, charge dissociation at the D/A interface into free charges, charge transport, and collection (extraction).…”