A power conversion efficiency (PCE) as high as 19.7% is achieved using a novel, low‐cost, dopant‐free hole transport material (HTM) in mixed‐ion solution‐processed perovskite solar cells (PSCs). Following a rational molecular design strategy, arylamine‐substituted copper(II) phthalocyanine (CuPc) derivatives are selected as HTMs, reaching the highest PCE ever reported for PSCs employing dopant‐free HTMs. The intrinsic thermal and chemical properties of dopant‐free CuPcs result in PSCs with a long‐term stability outperforming that of the benchmark doped 2,2′,7,7′‐Tetrakis‐(N,N‐di‐p‐methoxyphenylamine)‐9,9′‐Spirobifluorene (Spiro‐OMeTAD)‐based devices. The combination of molecular modeling, synthesis, and full experimental characterization sheds light on the nanostructure and molecular aggregation of arylamine‐substituted CuPc compounds, providing a link between molecular structure and device properties. These results reveal the potential of engineering CuPc derivatives as dopant‐free HTMs to fabricate cost‐effective and highly efficient PSCs with long‐term stability, and pave the way to their commercial‐scale manufacturing. More generally, this case demonstrates how an integrated approach based on rational design and computational modeling can guide and anticipate the synthesis of new classes of materials to achieve specific functions in complex device structures.

This article reviews various dopant-free hole transporting materials (HTMs) used in perovskite solar cells (PSCs) in three main categories including inorganic, polymeric, and small molecule HTMs. PSCs have undergone rapid progress, achieving power conversion efficiencies (PCEs) above 22%. With their low production cost and high efficiencies, PSCs are considered promising next-generation solar cell technology. In all developed architectures for PSCs, including planar and mesoscopic with conventional and inverted structures, HTMs play a significant role in determining the photovoltaic performance of PSCs. Using p-type dopants, however, is considered a common strategy to increase the hole conductivity of HTM, which is usually compensated by a more complicated fabrication procedure, higher production costs, and lower stability of PSC. Although several reviews on HTMs have been published, progress on dopant free HTMs needs to be reviewed and analyzed. Here, a review covering most of the published reports on dopantfree HTMs is presented, and the device structure and fabrication method, HTM layer deposition techniques, and the efficiency and the stability of PSCs are addressed during discussions in each main category. Finally, an outlook on stability and PCE growth in PSCs based on dopant-free HTMs is presented.

Single-atom catalysts (SACs) offer many advantages, such as atom economy and high chemoselectivity; however, their practical application in liquid-phase heterogeneous catalysis is hampered by the productivity bottleneck as well as catalyst leaching. Flow chemistry is a well-established method to increase the conversion rate of catalytic processes, however, SAC-catalysed flow chemistry in packed-bed type flow reactor is disadvantaged by low turnover number and poor stability. In this study, we demonstrate the use of fuel cell-type flow stacks enabled exceptionally high quantitative conversion in single atom-catalyzed reactions, as exemplified by the use of Pt SAC-on-MoS2/graphite felt catalysts incorporated in flow cell. A turnover frequency of approximately 8000 h−1 that corresponds to an aniline productivity of 5.8 g h−1 is achieved with a bench-top flow module (nominal reservoir volume of 1 cm3), with a Pt1-MoS2 catalyst loading of 1.5 g (3.2 mg of Pt). X-ray absorption fine structure spectroscopy combined with density functional theory calculations provide insights into stability and reactivity of single atom Pt supported in a pyramidal fashion on MoS2. Our study highlights the quantitative conversion bottleneck in SAC-mediated fine chemicals production can be overcome using flow chemistry.

New efficient hole‐transport material (HTM) composites based on low‐cost easy‐preparation non‐peripheral octamethyl‐substituted copper (II) phthalocyanine (N‐CuMe2Pc) nanowire and poly(3‐hexylthiophene) (P3HT) are developed for CH3NH3PbI3 (MAPbI3)‐based perovskite solar cells (PSCs). Compared with pristine P3HT, the prepared nanocomposite HTMs provided thin films with better qualities and reduced trap densities, and exhibited higher hole mobilities and well‐matched energy levels with the perovskite layer. Depending on the ratio of the two components, the power conversion efficiency (PCE) reached up to 16.61%, which is higher than the efficiency of the standard device based on doped spiro‐OMeTAD (16.13%). Moreover, the long‐term stability of the PSCs is also improving greatly. The best performing devices based on P1C1 HTM retained 90% of their initial efficiencies after 800 h of storage with a relative humidity of 75%. These results indicate N‐CuMe2Pc nanowire/P3HT nanocomposites can be an effective HTM to realize superior performance in PSCs.

We report the effect of water on the conversion of ethene with H-ZSM-5 to make aromatics at 300−500 °C. We found that water seriously decreased the conversion of ethene and the yield of aromatics, suppressed the hydrogen transfer reaction, and changed the distribution of aromatics at low reaction temperature (300 °C). However, the effect of water became relatively insignificant with an increase in the reaction temperature. Characterization by TGA, in situ FTIR, and GC-MS and a simulation with DFT validated that the cofed water preferentially adsorbs at the Brønsted acid site (BAS) of the H-ZSM-5 catalysts, in comparison to ethene, leading to the formation of Z−OH•••H 2 O hydrogen-bonded complexes and H + (H 2 O) n species. These species inside the channel of the zeolite inhibit the oligomerization of ethene, the olefin-induced hydrogen transfer reaction, and running of the hydrocarbon pool inside zeolite channels. We also validated that the conversion of ethene was recovered when the majority of H 2 O was desorbed from BAS, while the propagation of the HCP mechanism within HZSM-5 was still altered at higher temperature as a result of a physically adsorbed water-enhanced confinement effect in the channels. In addition, the role of water on the suppression of the amount of coke was investigated in detail.

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A common challenge for electrochemical ammonia synthesis in an aqueous phase is the consumption of Faradaic charge by the competing hydrogen evolution reaction (HER), which reduces the Faradaic efficiency for the desired conversion, i.e., the nitrate reduction reaction (NO 3 RR) to ammonium. This problem is particularly severe when a single-phase catalyst is operated at high current limits, thus a cocatalyst system that works synergistically for hydrogen acquisition and deoxygenation is needed to promote NO 3 RR over HER. Herein, we select a wellknown HER catalyst Mo 2 C and investigate how metal doping can switch its kinetics from HER-dominated to NO 3 RR-dominated pathways. At 3.8 wt % Ru doping of Mo 2 C, a 75% single pass conversion of nitrate (0.1 M) to ammonium in a 16 cm 2 flow electrolyzer was achieved, corresponding to an ammonium yield rate of 9.07 mmol h −1 at a full cell voltage of 2 V. As confirmed by DFT calculations and kinetic isotope experiments, ruthenium dopants in the matrix serve as the sink point for adsorbed hydrogen during NO 3 RR to promote the cooperative deoxygenation of *NO 3 and *NO 2 on the Ru−Mo cocatalytic site. Our study suggests that optimizing hydrogen acquisition and deoxygenation reactions in cocatalytic systems is an effective strategy for electrochemical synthesis.

Most metal−organic frameworks (MOFs) have an insulating nature due to their porosity and redox-inactive organic components. The electrical conductivity of the prototypical MOF, HKUST-1, can be tuned by infiltrating a small-molecule organic semiconductor, 7,7,8,8tetracyanoquinodimethane (TCNQ), into the HKUST-1 pores, creating TCNQ@HKUST-1. However, current processes of creating TCNQ@HKUST-1 films have many roadblocks such as slow crystallization rates, which limit high throughput production, and the formation of Cu(TCNQ) as a byproduct, which affects the electrical conductivity and degrades the chemical structure of HKUST-1. In this work, we show that HKUST-1 films can be rapidly synthesized over large areas with consistent thickness and no pinholes via a meniscus-guided coating technique called solution shearing. The subsequent pore activation process and TCNQ impregnation can be completed via solvent exchange to minimize the formation of the Cu(TCNQ) byproduct, and we obtain an increase in electrical conductivity of the solutionsheared TCNQ@HKUST-1 thin films of over 7 orders of magnitude, reaching a maximum value of 2.42 × 10 −2 S m −1 when TCNQ is incorporated for 10 days.