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Shuffling is a time-randomized countermeasure against side-channel attacks. To achieve effective protections, shuffling is usually combined with other countermeasures, such as the masking. It requires the shuffling to be as efficient as possible. In this work, we describe an instruction set extensions (ISEs) for shuffling countermeasure. Our ISEs focuses on the generation of random permutations, which is the most difficult part to deploy the shuffling in microprocessors. The Thorp shuffling is implemented in hardware, enabling the instruction to generate random permutations. We design new ISEs compatible to the RISC-V standard instruction set format. Then, we present applications of our ISEs by giving two combinations of shuffling and masking, which can be regarded as promising software–hardware co-designs of side-channel countermeasures. At last, we embed the ISEs to the RISC-V core called tinyriscv, and evaluate the silicon overhead and the side-channel security of the shuffled masked AND operation. The evaluation shows that the new instruction can significantly improve the security of masking countermeasures.

Compared with their three-dimensional (3D) counterparts, low-dimensional metal halide perovskites (2D and quasi-2D; B2An−1MnX3n+1, such as B = R-NH3+, A = HC(NH2)2+, Cs+; M = Pb2+, Sn2+; X = Cl−, Br−, I−) with periodic inorganic–organic structures have shown promising stability and hysteresis-free electrical performance1–6. However, their unique multiple-quantum-well structure limits the device efficiencies because of the grain boundaries and randomly oriented quantum wells in polycrystals7. In single crystals, the carrier transport through the thickness direction is hindered by the layered insulating organic spacers8. Furthermore, the strong quantum confinement from the organic spacers limits the generation and transport of free carriers9,10. Also, lead-free metal halide perovskites have been developed but their device performance is limited by their low crystallinity and structural instability11. Here we report a low-dimensional metal halide perovskite BA2MAn−1SnnI3n+1(BA, butylammonium; MA, methylammonium; n= 1, 3, 5) superlattice by chemical epitaxy. The inorganic slabs are aligned vertical to the substrate and interconnected in a criss-cross 2D network parallel to the substrate, leading to efficient carrier transport in three dimensions. A lattice-mismatched substrate compresses the organic spacers, which weakens the quantum confinement. The performance of a superlattice solar cell has been certified under the quasi-steady state, showing a stable 12.36% photoelectric conversion efficiency. Moreover, an intraband exciton relaxation process may have yielded an unusually high open-circuit voltage (VOC).

Organometallic halide perovskites attract strong interests for their high photoresponsivity and solar cell efficiency. However, there was no systematic study of their power- and frequency-dependent photoresponsivity. We identified two different power-dependent photoresponse types in methylammonium lead iodide perovskite (MAPbI3) photodetectors. In the first type, the photoresponse remains constant from 5 Hz to 800 MHz. In the second type, absorption of a single photon can generate a persistent photoconductivity of 30 pA under an applied electric field of 2.5 × 104V/cm. Additional absorbed photons, up to 8, linearly increase the persistent photoconductivity, which saturates with the absorption of more than 10 photons. This is different than single-photon avalanche detectors (SPADs) because the single-photon response is persistent as long as the device is under bias, providing unique opportunities for novel electronic and photonic devices such as analogue memories for neuromorphic computing. We propose an avalanche-like process for iodine ions and estimate that absorption of a single 0.38 aJ photon triggers the motion of 108–9ions, resulting in accumulations of ions and charged vacancies at the MAPbI3/electrode interfaces to cause the band bending and change of electric material properties. We have made the first observation that single-digit photon absorption can alter the macroscopic electric and optoelectronic properties of a perovskite thin film.

Metal–octaaminophthalocyanine (MOAPc)-based 2D conductive metal–organic frameworks (cMOFs) have shown great potential in several applications, including sensing, energy storage, and electrocatalysis, due to their bimetallic characteristics. Here, we report a detailed metal substitution study on a family of isostructural cMOFs with Co2+, Ni2+, and Cu2+as both the metal nodes and the metal centers in the MOAPc ligands. We observed that different metal nodes had variations in the reaction kinetics, particle sizes, and crystallinities. Importantly, the electronic structure and conductivity were found to be dependent on both types of metal sites in the 2D cMOFs. Ni-NiOAPc was found to be the most conductive one among the nine possible combinations with a conductivity of 54 ± 4.8 mS/cm. DFT calculations revealed that monolayer Ni-NiOAPc has neither the smallest bandgap nor the highest charge carrier mobility. Hence its highest conductivity stems from its high crystallinity. Collectively, these results provide structure property relationships for MOAPc-based cMOFs with amino coordination units.

A series of low‐bandgap alternating copolymers of dithienosilole and thienopyrrolodione (PDTSTPDs) are prepared to investigate the effects of the polymer molecular weight and the alkyl chain length of the thienopyrrole‐4,6‐dione (TPD) unit on the photovoltaic performance. High‐molecular‐weight PDTSTPD leads to a higher hole mobility, lower device series resistance, a larger fill factor, and a higher photocurrent in PDTSTPD:[6,6]‐phenyl C71butyric acid methyl ester (PC71BM) bulk‐heterojunction solar cells. Different side‐chain lengths show a significant impact on the interchain packing between polymers and affect the blend film morphology due to different solubilities. A high power conversion efficiency of 7.5% is achieved for a solar cell with a 1.0 cm2active area, along with a maximum external quantum efficiency (EQE) of 63% in the red region.

To investigate the side chain effect on the photovoltaic performance of conjugated copolymers with alternating electron push–pull structures, three alternating copolymers (O–HD, BO–BO, and PU–O) of benzodithiophene and dithienyldiketopyrrolopyrrole were designed and synthesized. They were nomenclated based on the side chains on the benzodithiophene (BDT) and the diketopyrrolopyrrole (DPP) units, which are octyl (O) and 2-hexyldecyl (HD); 3-butyloctyl (BO), and 2-butyloctyl (BO): and 3-pentylundecyl (PU) and octyl (O) groups, respectively. The total C number of the side chains in each repeat unit was kept at 48 to control the dilute effect. The solubility, optical, and electrochemical properties, and crystalline structure of the polymers were depended on the combination of these linear or branched alkyl chains. Thin film transistor (TFT) characterization showed that PU–O had the best hole mobility up to 1.6 × 10–3cm2V–1s–1. The best photovoltaic performance was observed from O–HD with power conversion efficiency (PCE) up to 4.1%. However, it only showed a modest hole mobility of 3.8 × 10–4cm2V–1s–1, about 4-fold lower than PU–O. This dramatically different performance of these polymers for TFT and photovoltaic devices was explained by the interaction at the interface of the polymer electron donor and the PCBM acceptor domains.

The thermal optical coefficient (TOC) and volume thermal expansion coefficient (TEC or β) of poly(methyl methacrylate) (PMMA) polymers doped with azobenzene dyes were investigated. A novel approach for determining the TEC has been suggested and a non-linear variation in the TOC with increasing wt% of the dopant has been observed and tentatively explained. In addition, the refractive index (RI) contrast necessary for forming a waveguide was demonstrated to be easily achievable by adding a higher-refractive-index material to the blank polymer. Copyright © 2000 John Wiley & Sons, Ltd.

The hydroxyl groups formed during the reaction of DGEBA (diglycidyl ether of bisphenol A) and aniline are used for the first time to form crosslinkable polyurethane. The very active diisocyanate groups as a pure reagent are only introduced to the reaction system at the last step of the crosslinking reaction, which greatly improves the preparation procedure. A very good film-forming property was found and a d33 value as high as 320 pm V⁻ was measured for the poled polymer film. Copyright © 2000 John Wiley & Sons, Ltd.