Organic photovoltaics (OPVs) have potential to become cost-efficient, low-energy consumption, and environmentally friendly renewable energy sources. A key parameter to determine the performance of OPVs is fill factor (FF). We review theoretical deduction as well as practical approaches to enhance FF. At present, the performance and FF of OPVs have reached above 11% and 75%, respectively.

Electronic skin sensing devices are an emerging technology and have substantial demand in vast practical fields including wearable sensing, robotics, and user‐interactive interfaces. In order to imitate or even outperform the capabilities of natural skin, the keen exploration of materials, device structures, and new functions is desired. However, the very high resistance and the inadequate current switching and sensitivity of reported electronic skins hinder to further develop and explore the promising uses of the emerging sensing devices. Here, a novel resistive cloth‐based skin‐like sensor device is reported that possesses unprecedented features including ultrahigh current‐switching behavior of ≈107 and giant high sensitivity of 1.04 × 104–6.57 × 106 kPa−1 in a low‐pressure region of <3 kPa. Notably, both superior features can be achieved by a very low working voltage of 0.1 V. Taking these remarkable traits, the device not only exhibits excellent sensing abilities to various mechanical forces, meeting various applications required for skin‐like sensors, but also demonstrates a unique competence to facile integration with other functional devices for various purposes with ultrasensitive capabilities. Therefore, the new methodologies presented here enable to greatly enlarge and advance the development of versatile electronic skin applications.

We demonstrate here that the nanostructure of poly(3-hexylthiophene) and [6,6]-phenyl-C61-butyric acid methyl ester (P3HT/PCBM) bulk heterojunction (BHJ) can be tuned by inorganic nanoparticles (INPs) for enhanced solar cell performance. The self-organized nanostructural evolution of P3HT/PCBM/INPs thin films was investigated by using simultaneous grazing-incidence small-angle X-ray scattering (GISAXS) and grazing-incidence wide-angle X-ray scattering (GIWAXS) technique. Including INPs into P3HT/PCBM leads to (1) diffusion of PCBM molecules into aggregated PCBM clusters and (2) formation of interpenetrating networks that contain INPs which interact with amorphous P3HT polymer chains that are intercalated with PCBM molecules. Both of the nanostructures provide efficient pathways for free electron transport. The distinctive INP-tuned nanostructures are thermally stable and exhibit significantly enhanced electron mobility, external quantum efficiency, and photovoltaic device performance. These gains over conventional P3HT/PCBM directly result from newly demonstrated nanostructure. This work provides an attractive strategy for manipulating the phase-separated BHJ layers and also increases insight into nanostructural evolution when INPs are incorporated into BHJs.

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The present research demonstrates a facile one-pot heating process without injection to synthesize an important light harvesting quaternary nanocrystal: wurtzite copper-zinc-tin sulfide (w-CZTS). High quality w-CZTS nanocrystals can be easily obtained by mixing all the precursors and simply heating to the reaction temperature. The nano-crystal formation mechanism is thoroughly investigated and resolved by X-ray diffraction spectroscopy (XRD), transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS). It starts with the nucleation of plasmonic djurleite Cu 1.94 S, subsequent growth of CZTS-Cu 1.94 S heterostructures and inter-diffusion of cations and then finally leads to single phase and single crystal w-CZTS nanocrystals. The mechanism of nanocrystal formation can be applied universally regardless of the type of zinc and tin precursor for high quality w-CZTS nanocrystals. The in-depth interpretations of the reaction mechanism of this process significantly advance the current knowledge of multi-component nanocrystal formation. The developed method is scalable for high throughput and low cost w-CZTS suspensions which await practical photovoltaic applications.

Anionic and cationic defects are considered as one of the crucial factors that affect carrier transport property and degradation of perovskite photovoltaic materials. Herein, we demonstrate a simple passivation of hot casted perovskite film in air by a dipolar ion, 2-thiophene ethylammonium chloride (TEACl), showing enhanced power conversion efficiency (PCE) of solar cell from 15.44% to 18.84% with increased open circuit voltage (V oc) by 50 mV. The dipolar ion of TEACl can simultaneously passivate both cationic and anionic defects. Space charge limited current model, Urbach energy analysis, and photoluminescence spectroscopy were conducted and revealed that the defects passivated by TEACl reduced the defects density of perovskite films, nonradiative recombination, and electronic disorder. In addition, the device with TEACl passivation exhibited outstanding stability of power output (<0.1% decay) as compared with the device without passivation (>8% decay) from the 300 s measurement of current verse time plots (J–T plots) at 65% relative humidity and 50 °C in air. The 80% of initial PCE was maintained after 700 h storage. As compared to conventional passivation approaches which are typically carried out at complicated crystallization step of perovskite, this post-treatment process can be easily done on the crystallized perovskite film. This facile approach is upscale and compatible with conventional coating techniques such as slot-die coating, spray, etc. for high-quality perovskite film.

Inorganic−organic hybrid perovskite single crystals are potential materials for the application of high performance optoelectronic devices. The exposed surface of single crystals can dramatically affect the measured properties. Facet-dependent behaviors are also speculated. However, impeded by the lack of facile facet engineering strategy for inorganic−organic hybrid perovskites, the relationship between different facets and respective performance remains elusive. In this work, we present a simple approach of ligandmediated crystal growth to control the shape and the exposed facets of methylammonium lead iodide single crystals. The addition of oleylamine ligand can trigger the continuous morphological transition from dodecahedral-shaped single crystal enclosed by (100) T and ( 112) T to cubic-shaped single crystal enclosed by (110) T and (002) T while maintaining the material composition and crystalline phase. We fabricated single crystal based photodetectors and carried out the first unambiguous study on the relationship between facet structure and device performance. This report opens a new paradigm to reveal the facetdependent properties and to enhance the device performance of single crystal.

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