Two-dimensional (2D) perovskites are emerging photovoltaic materials because of their highly tunable photophysical properties and improved environmental stability in comparison with 3D perovskites. Here, a thiophene-based bulky dication spacer, namely, 2,5-thiophenedimethyl­ammonium (ThDMA), was developed and applicated in 2D Dion–Jacobson (DJ) perovskite. High-quality 2D DJ perovskite, (ThDMA)­(MA) n–1Pb n I3n+1 (nominal n = 5), with improved crystallinity, preferred vertical orientation, and enlarged spatially resolved carrier lifetime could be achieved by a one-step method using a mixed solvent of DMF/DMSO (v/v, 9:1). The optimized device exhibits a high efficiency of 15.75%, which is a record for aromatic spacer-based 2D DJ perovskite solar cells (PSCs). Moreover, the unencapsulated 2D DJ perovskite devices sustained over 95% of their original efficiency after storage in N2 for 1655 h. Importantly, both the light-soaking stability and thermal stability (T = 80 °C) of the 2D DJ perovksite devices are dramatically improved in comparison with their 3D counterparts. These results indicate that highly efficient and stable 2D DJ PSCs could be achieved by developing thiophene-based aromatic spacers as well as device engineering.

Layered two-dimensional (2D) perovskites are emerging photovoltaic materials due to their good environmental and structural stability thanks to the bulky organic spacers incorporated in the crystal lattice. Formamidine (FA) is an indispensable organic cation in high-performance 3D perovskite materials, whereas FA derivative-based spacers have remained largely unexplored in 2D perovskite. Here, we demonstrated a class of aromatic formamidinium (ArFA) spacers, namely, benzamidine (PhFA) and para-fluorobenzamidine (p-FPhFA), for efficient 2D Ruddlesden–Popper (RP) perovskite solar cells. It is found that the 2D perovskite with the fluorinated spacer p-FPhFA shows significantly improved charge carrier lifetime, enhanced mobility, and reduced trap density in comparison with an unfluorinated PhFA spacer. As a result, the p-FPhFA-based 2D perovskite (n = 5) device yields a champion efficiency of 17.37%, which is much higher than that of the PhFA-Pb device (12.92%), representing a record value for 2D PSCs with FA-based spacers. These results highlight the great potential of ArFA spacers, especially the fluorinated ArFA spacer, for high-performance 2D perovskite solar cells.

Two-dimensional Dion–Jacobson (DJ) perovskites have shown improved structure stability in comparison with Ruddlesden–Popper (RP) perovskites. However, the mechanism behind the improved stability is still largely unexplored. Here a multifluorinated aromatic spacer, namely, 4F-PhDMA, has been successfully developed for 2D DJ perovskites. It is found that the 2D DJ perovskite with a 4F-PhDMA spacer exhibits a high dissociation energy due to the multiple noncovalent interactions. The optimized 2D DJ device based on the 4F-PhDMA spacer (n = 4) exhibits a champion efficiency of 16.62% with much improved light and thermal stability. This efficiency is much higher than that of the control device using an unfluorinated spacer (n = 4, PCE = 10.11%) and is among the highest efficiencies in aromatic-spacer-based 2D DJ perovskite solar cells (PSCs). Our work highlights the importance of incorporating multiple noncovalent interactions in the 2D DJ perovskite by employing a multifluorinated aromatic spacer to achieve DJ PSCs with both high efficiency and high stability.

Abstract.A semi-active suspension design based on the traditional method of skyhook control is not capable of effectively controlling the attitude of the vehicle. However, an innovative approach called decoupling skyhook control allows the attitude of the vehicle body and its vibration characteristics to be effectively controlled. In this paper, a new decoupling skyhook controller for semi-active suspension is presented. Vehicle body motions in the three directions of vertical, pitch, and roll have been adopted to develop three skyhook controllers and directly control the vehicle body attitude. Furthermore, three orientation skyhook control forces are converted into actual damping forces of four adjustable dampers through the input decoupling transformation. The simulation results show that the developed controller is more effective than the traditional skyhook control in improving ride comfort.Keywords: Skyhook control, Input decoupling, Semi-active suspension. IntroductionSince the skyhook control scheme was introduced in the early 1970s by D. Karnopp, this method has been used in many vibration isolation applications [1]. In active and semi-active suspension control, the skyhook control scheme is an extremely effective control strategy and has been used in some commercial applications. Moreover, the skyhook scheme is often used as the reference model for other control strategies because of its simplicity and its prominent effect in improving ride comfort [2][3][4].To develop the semi-active control algorithm for a full-vehicle system, two different methodologies can be used [5]. One methodology uses the quarter car model to develop the control algorithm, which is then implemented in a full vehicle model for controlling and analysis [6][7][8]. However, this methodology does not directly consider the pitch and roll motions of the vehicle. Furthermore, four accelerometers on the four corner points of the sprung mass are usually used to design controllers. As the aim of the suspension is to control the acceleration felt by the passengers, this acceleration should be considered at the vehicle's center of gravity and not over the wheels. Thus, the control of the body posture may be inadequate.Another methodology uses a full-vehicle model to directly control both the vertical motion (heave) and the angular motion (pitch and roll) of the vehicle body [9,10]. The advantage of this methodology is that a control strategy can be designed that effectively controls the attitude of the sprung mass and suppresses the vibration of the suspension. In [9], three fuzzy controllers are designed to produce three forces z f ,  f and  f to suppress the heave, pitch, and roll

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