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Summary Halide perovskites have emerged as a new class of inorganic-based soft semiconductors that are revolutionizing the field of (opto)electronics. However, the fundamental structures and properties or functions of halide perovskites are still far from being fully understood, calling for the need of precise, quantitative, and high-spatiotemporal-resolution characterizations. As one of the most powerful multimodal characterization techniques, synchrotron radiation offers high-brilliance X-ray beams for high-resolution observations across multiple length scales obtained within extremely short time spans. Performing a brief review of synchrotron-based perovskite studies in the literature, here we provide perspectives on the use of synchrotron characterizations not only for studying multiple-length-scale structures and dynamic variations of perovskite materials, but also for in situ monitoring of device functions and dynamics. The goal of this perspective is to present many capabilities and evoke emerging opportunities of synchrotron characterizations for providing decisive answers to the outstanding science problems in the perovskite field, pushing forward the technological development.

We synthesized a planar pDPPTTi-OD polymer based on diketopyrrolopyrrole (DPP) and thieno [2,3- b ]thiophene (TTi) and investigated the electrical properties of the pDPPTTi-OD polymer. pDPPTTi-OD films displayed a low optical bandgap of 1.57 eV, and HOMO and LUMO levels of −5.40 and −3.74 eV, respectively. The 150°C-annealed pDPPTTi-OD films showed a high hole mobility of 0.16 cm 2 V −1 s −1 in organic thin-film transistor (OTFT) devices. The photovoltaic properties of polymer solar cells (PSCs) incorporating the pDPPTTi-OD were also measured. A pDPPTTi-OD:PC 71 BM blend film was spin-coated at 25, 70 and 90 °C. High-temperature processing significantly improved the power conversion efficiency of PSCs by effectively reducing the PC 71 BM domain sizes, which improved the miscibility between pDPPTTi-OD and PC 71 BM. This work demonstrated that the TTi moiety is a useful donor building block for high- performance D–A type polymers in OTFTs and PSCs, and that processing temperatures should be controlled to fully realize the materials' beneficial intrinsic properties.

The fused dithieno[2,3- d :2′,3′- d ′]benzo[1,2- b :4,5- b ′]dithiophene (DTBDT) structure was coupled with diketopyrrolopyrrole (DPP) moieties to generate highly planar bis(2,5-bis(2-ethylhexyl)-3,6-di(thiophen-2-yl)-2,5-dihydropyrrolo[3,4- c ]pyrrole-1,4-dione)dithieno[2,3- d :2′,3′- d ′]benzo[1,2- b :4,5- b ′]dithiophene (DTBDTDPP-EH) and bis(2,5-bis(2-butyloctyl)-3,6-di(thiophen-2-yl)-2,5-dihydropyrrolo[3,4- c ]pyrrole-1,4-dione)dithieno[2,3- d :2′,3′- d ′]benzo[1,2- b :4,5- b ′]dithiophene (DTBDTDPP-BO) molecules, where the EH and BO stands for 2-ethylhexyl and 2-butyloctyl groups respectively. The morphology of the DTBDTDPP-EH alone or DTBDTDPP-EH:[6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM) blend film was controlled using post-thermal annealing at 130 °C or addition of 1,8-diiodooctane (DIO) additives. The DIO-additive treatment was more effective than thermal annealing at increasing crystallinity; the DIO-additives promoted the formation of nanoscopically well-connected molecular crystalline domains in the blend films. This observation well explained the ordering of the photovoltaic properties of DTBDTDPP-EH:PCBM devices: from worst to best, as-cast, thermally treated, and DIO-treated photoactive films. The DTBDTDPP-BO:PCBM device followed the similar trend with lower performances due to the presence of irregularly overgrown domains. Overall, we demonstrate that it is critical to optimize nanoscale film morphologies by engineering alkyl chains and selecting an appropriate processing method.

We fabricated well-defined 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-PEN) crystal arrays for use in electronic applications via a simple but effective method, the confined evaporative capillary flow (CEC) method. This has been accomplished by systematically controlling the contact line pinning at the edge of glass stylus and the outward hydrodynamic flow within the drying droplet with various processing solvents and surface properties of the substrate during solidification. We found that after CEC coating of TIPS-PEN solution dissolved into toluene onto SiO 2 surface, ribbon-shaped TIPS-PEN crystals were well developed with a width of 20–100 μm and length of 300 μm – 2 mm, which is presumably owing to optimized capillary evaporation. Specifically, TIPS-PEN crystals present highly preferred crystal orientation along the ( l 0 0) axis, which can lead to efficient charge transport in a lateral direction. Thus, TIPS-PEN field-effect transistors (FETs) exhibited a good hole mobility of 0.72 cm 2 /Vs.

We study the glass transition temperature and the crystallization in PEO-based polymer electrolytes with addition of siloxane nanoparticles of 6 , the molar ratio for maximum conductivity. Differential scanning calorimetry and wide angle X-ray scattering results show that siloxane nanoparticles reduce the crystallization of PEO by increasing the amount of complexes of ethylene oxide (EO) and Li ions in PEO-LiPF 6 . In contrast to other additives, the glass transition temperature of the electrolyte is lowered with increasing concentration of siloxane nanoparticles. Enhancement of the conductivity with siloxane nanoparticles is due to the increased ion mobility and amorphous area in electrolytes.

We report the process of thermal degradation of organic light emitting devices (OLEDs) having multilayered structure of [LiF/tris-(8-hydroxyquinoline) aluminum(Alq 3 )/ N , N ′-Bis(naphthalen-1-yl)- N , N ′-bis(phenyl)benzidine (NPB)/copper phthalocyanine (CuPc)/indium tin oxide (ITO)/SiO 2 on a glass] by synchrotron X-ray scattering. The results show that the thermally induced degradation process of OLED multilayers has undergone several evolutions due to thermal expansion of NPB, intermixing between NPB, Alq 3 , and LiF layers, dewetting of NPB on CuPc, and crystallization of NPB and Alq 3 depending on the annealing temperature. The crystallization of NPB appears at 180 °C, much higher temperature than the glass transition temperature ( T g = 96 °C) of NPB. The results are also compared with the findings from the atomic force microscope (AFM) images.