Polymerized Naphthalimide Derivatives as Remarkable Electron‐Transport Layers for Inverted Organic Solar Cells

Abstract

Two polymerized naphthalimide derivatives, named as N-TBHOB and N-DBH, are prepared by quaternization. They exhibit excellent performance as electron-transport layers (ETLs) in inverted organic solar cells (i-OSCs). The results indicate N-TBHOB with a reticulated structure owns a superior performance on electron extraction, electron transport, thickness tolerance, and less carrier recombination compared with N-DBH with linear structure. The i-OSCs based on N-TBHOB with PTB7-Th:PC 71 BM as the active layer achieve power conversion efficiencies (PCEs) of 10.72% and 10.03% under the thickness of 11 and 48 nm respectively, which indicates N-TBHOB possesses better thickness tolerance than most of organic ETLs in i-OSCs. N-TBHOB also shows more competent performance than N-DBH and ZnO in nonfullerene i-OSCs for comprehensively improved J sc , V oc , and fill factor (FF) values. Its i-OSC with PM6:Y6 blend presents a high PCE of 16.78%. The study provides an efficient strategy to prepare ETLs by combining conjugated and nonconjugated units with a reticulated structure in the backbone for high-performance i-OSCs.

Decreasing the Molecular Polarity of Naphthalimide by a π-Bridge Strategy as Cathode Interlayers to Enable High-Efficient Electron Transfer in Organic Solar Cells

“…Yet, shortcomings such as poor processability and stability result in films that are inhomogeneous in composition and continuity. ,, To address these challenges, researchers have developed a range of new CILs aimed at improving the stability and PCE of Y6-based OSCs. − For instance, Xie et al synthesized a series of diimide-based molecules with special functional groups that complex Zn 2+ after deprotonation . Additionally, certain organic materials have been proven to be efficient in inverted devices. − These CILs must possess the ability to increase the physical contact between components while simultaneously lowering the WF of the cathode in OSCs. However, it is important to note that highly polar groups in interfacial molecules can lead to high interfacial tension between blends and interlayers, which is not beneficial for enhancing the performance of devices. , Therefore, it is crucial for high-quality CILs to have low molecular polarity and appropriate energy levels and to maintain moderate crystallization. ,, …”

Tuning the charge stabilization and transport in naphthalimide-based semiconductors via a fused-ring and core-engineering strategy

“…24,25 On the one hand, imide units, and more specifically naphthalimide derivatives, are often used as strong electron-acceptor moieties to obtain processable organic materials with low-lying LUMO energy levels and good optical, electrochemical and electrical properties. [26][27][28][29][30] On the other hand, the covalent linkage of naphthalimide units with strong donor scaffolds such as oligothiophenes or triarylamines has shown to be a promising approach to obtain ambipolar materials. 31,32 Thus, in our research groups we have widely demonstrated that the combination of donor and acceptor units through different rigid and conjugated linkers can pave the way to functional materials with tunable and, sometimes unexpected, optical and electrochemical properties and good n-type or ambipolar characteristics in OFETs or OSCs.…”

A robust and thickness-insensitive hybrid cathode interlayer for high-efficiency and stable inverted organic solar cells

“…Unfortunately, the PEDOT:PSS AIL is seriously unfavorable to the stability of devices, and PDI/NDI based thickness-insensitive CILs are rarely reported for inverted OSCs with the advantage of stability, which may originate from relatively poor solvent resistance and transparency of PDI/NDI based CILs. 28 In inverted OSCs, zinc oxide (ZnO) is a widely used CIL, and PDI/NDI derivatives, e.g. PBI materials, were also doped into ZnO as thickness-insensitive CILs.…”