Small-Molecule Electron Transport Layer with Siloxane-Functionalized Side Chains for Nonfullerene Organic Solar Cells

Abstract

Active layer materials with silicone side chains have been broadly reported to have excellent long-term stability in harsh environments. However, the application of conjugated materials with silicone side chains in electron transport layers (ETLs) has rarely been reported. In this research, we synthesized for the first time a siloxane-modified perylene-diimide derivative (PDI-OSi) consisting of a side-chain substituent of siloxane and a conjugated group of perylene-diimide (PDI). The inserted siloxane functional groups not only can strengthen the light transmittance of PDI-OSi but also can remarkably expand its solubility and improve the filmforming ability and air stability of the material. Second, introducing siloxane-containing side chains can dramatically lower the work function and interfacial barrier of the electrode, thereby achieving a favorable ohmic contact. In addition, the moderate surface energy of siloxane functional groups makes PDI-OSi hydrophobic, which is conducive to forming excellent miscibility with hydrophobic active layers to promote charge transfer. When PDI-OSi is used as an ETL in organic solar cells (OSCs), operative exciton dissociation and more favorable surface morphology enable OSCs to realize a power conversion efficiency (PCE) of 13.99%. These results indicate that side-chain engineering with siloxane pendants is a facile strategy for constructing efficient OSCs.

Intramolecular Lock Conjugated Polymer Electrolytes as the Cathode Interfacial Layer for Nonfullerene Organic Solar Cells

“…This interaction enhances the electron affinity of the molecule, thus promoting the efficient transfer of electrons. When acting as CILs, they can form an intermolecular electric field (IEF) from the active layer to the CIL at the active layer/cathode interface, which can effectively facilitate the transport of electrons from the active layer to the cathode. , According to the results of theoretical calculation (Figure S12), it can be observed that the lowest unoccupied molecular orbitals (LUMO) of PFPy-BT and PFPy-TTBT molecules are principally concentrated in the benzothiadiazole unit, while the highest occupied molecular orbitals (HOMO) are primarily concentrated in the conjugate main chain. In contrast, the HOMO and LUMO of PFPy-TT are concentrated in the polymer backbone.…”

“…When acting as CILs, they can form an intermolecular electric field (IEF) from the active layer to the CIL at the active layer/cathode interface, which can effectively facilitate the transport of electrons from the active layer to the cathode. 26,66 According to the results of theoretical 34 In contrast to the UV−vis spectra of PFPy-BT and PFPy-TTBT in solutions, redshifts are found in the corresponding film spectra due to molecular aggregation.…”

“…Lately, organic CILs have acquired significant advance in enhancing the performances of NOSCs. Among them, various organic CILs such as polyethylenimine (PEI) and its derivatives, − perylene diimide (PDI) and naphthalene diimide (NDI) derivatives, − and poly­[(9,9-bis­(3′-( N , N -dimethylamino)­propyl)-2,7-(2,9-dioctylamino)] (PFN) and so forth have demonstrated excellent properties. In particular, fluorene compounds with excellent conjugated structures play a dramatic role in the development of CILs.…”

Perylene-diimide for organic solar cells: current scenario and prospects in molecular geometric, functionalization, and optoelectronic properties

“…For example, PDI's imide and bay sites benet greatly from the addition of branched alkyl chains or aromatic groups. [94][95][96][97][98] Moreover, the incorporation of heteroatoms into the perylene-conjugated skeleton produces donor/acceptor surfaces with increased electrical interactions, which in turn reduces the amount of energy required to bind polaron pairs. An efficient method for controlling optical absorption and other properties, such as energy level, charge transport, and crystallinity, is to use a conjugated linker or bridge as a link between multiple PDI moieties in twisted 2D/3D.…”

Recent Advances of Benzodithiophene‐Based Donor Materials for Organic Solar Cells

“…Side‐chain engineering can help adjust the crystallinity of PDMs to further improve their stability. [ 106 ] Developing active layer materials, [ 107 ] interfacial engineering, [ 108 ] and optimizing processing technology [ 109 ] are practical paths to accelerate device stability by optimizing interfacial morphology. In addition, proper packaging of the OSCs is a pivotal technology to avoid instability caused by high humidity and oxygen.…”