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Achieving both high redox activity and rapid ion transport is a critical and pervasive challenge in electrochemical energy storage applications. This challenge is significantly magnified when using large‐sized charge carriers, such as the sustainable ammonium ion (NH4+). A self‐assembled MXene/n‐type conjugated polyelectrolyte (CPE) superlattice‐like heterostructure that enables redox‐active, fast, and reversible ammonium storage is reported. The superlattice‐like structure persists as the CPE:MXene ratio increases, accompanied by a linear increase in the interlayer spacing of MXene flakes and a greater overlap of CPEs. Concurrently, the redox activity per unit of CPE unexpectedly intensifies, a phenomenon that can be explained by the enhanced de‐solvation of ammonium due to the increased volume of 3 Å‐sized pores, as indicated by molecular dynamic simulations. At the maximum CPE mass loading (MXene:CPE ratio = 2:1), the heterostructure demonstrates the strongest polymeric redox activity with a high ammonium storage capacity of 126.1 C g−1 and a superior rate capability at 10 A g−1. This work unveils an effective strategy for designing tunable superlattice‐like heterostructures to enhance redox activity and achieve rapid charge transfer for ions beyond lithium. [ABSTRACT FROM AUTHOR]

Poly(Phenylene vinylene) anionic polyelectrolyte (PVBT‐SO3) was found to be an efficient hole extraction layer for inverted perovskite solar cells. It can be cast from an aqueous solution and does not require thermal annealing for improved device performance. The devices show maximum solar cell efficiency of 15.9% and exhibit improved stability under ambient conditions and enhanced charge extraction. [ABSTRACT FROM AUTHOR]

Low-temperature solution-processed high-efficiency colloidal quantum dot (CQD) photovoltaic devices are developed by improving the interfacial properties of p-n heterojunctions. A unique conjugated polyelectrolyte, WPF-6-oxy-F, is used as an interface modification layer for ZnO/PbS-CQD heterojunctions. With the insertion of this interlayer, the device performance is dramatically improved. The origins of this improvement are determined and it is found that the multifunctionality of the WPF-6-oxy-F interlayer offers the following essential benefits for the improved CQD/ZnO junctions: (i) the dipole induced by the ionic substituents enhances the quasi-Fermi level separation at the heterojunction through favorable energy band-bending, (ii) the ethylene oxide groups containing side chains can effectively passivate the interfacial defect sites of the heterojunction, and (iii) these effects occur without deterioration in the intrinsic depletion region or the series resistance of the device. All of the figures-of-merit of the devices are improved as a result of the enhanced built-in potential (electric field) and the reduced interfacial charge recombination at the heterojunction. The benefits due to the WPF-6-oxy-F interlayer are generally applicable to various types of PbS/ZnO heterojunctions. Finally, CQD photovoltaic devices with a power conversion efficiency of 9% are achievable, even by a solution process at room temperature in an air atmosphere. The work suggests a useful strategy to improve the interfacial properties of p-n heterojunctions by using polymeric interlayers. [ABSTRACT FROM AUTHOR]

By coating conjugated polyelectrolytes (CPEs) on metals, the work function (WF) of metals can be tuned by electric dipoles formed through the selfassembly of cation-anion pairs on the side chains of CPEs. Recently, it has been reported that a pertinent oxidative doping of anionic CPEs results in a reversed direction in the net electric dipoles, thereby yielding opposite WF tunability compared with pristine CPEs. However, the fundamental mechanism of this reversed WF tunability is not clearly understood. Here, through a systematic study of the relationship between the chemical structure of anionic CPEs (n-type) and the corresponding oxidation-processed CPEs (p-type), it is clearly demonstrated that radical cations are generated on the π-conjugated backbone of the n-type CPEs and strongly paired with anions on the side chains of the n-type CPEs, thereby reversing the direction of the total net electric dipoles. Furthermore, it is found that the degree of radical cation-anion coupling in the CPEs is a key factor in determining their WF tunability. It is envisioned that the results will provide a fundamental understanding of CPEs for versatile interface engineering in organic electronics. [ABSTRACT FROM AUTHOR]

p‐Type conjugated polyelectrolytes (CPEs) are developed as organic‐based work‐function‐modifier materials for the broad work‐function (WF) tunability of various metal electrodes. Facile oxidative treatments of n‐type CPEs using various oxidants produce unprecedented p‐type CPEs with reversed electronic properties corresponding to n‐type CPEs, resulting in fine WF tuning of adjacent metal electrodes. This change leads to substantial increases in power conversion efficiency and lifetime of organic solar cells. [ABSTRACT FROM AUTHOR]

In the field of polymer solar cells, improving photovoltaic performance has been the main driver over the past decade. To achieve high power conversion efficiencies, a plethora of new photoactive donor polymers and fullerene derivatives have been developed and blended together in bulk heterojunction active layers. Simultaneously, further optimization of the device architecture is also of major importance. In this respect, we report on the use of specific types of electron transport layers to boost the inherent I- V properties of polymer solar cell devices, resulting in a considerable gain in overall photovoltaic output. Imidazolium-substituted polythiophenes are introduced as appealing electron transport materials, outperforming the currently available analogous conjugated polyelectrolytes, mainly by an increase in short-circuit current. The molecular weight of the ionic polythiophenes has been identified as a crucial parameter influencing performance. [ABSTRACT FROM AUTHOR]