We prepared the novel fullerene derivative (a-bis-PCBM) by separating it from the as-produced bis-phenyl-C 61 -butyric acid methyl (bis-[60] PCBM) ester isomer mixture using preparative peak-recycling high performance liquid chromatography (HPLC). We employed the compound as a templating agent for the solution processing of metal halide perovskite films by the antisolvent method. Perovskite solar cells (PSCs) containing a-bis-PCBM perovskite achieve better stability, efficiency, and reproducibility compared with those employing traditional PCBM. The a-bis-PCBM can fill the vacancies and grain boundaries of the perovskite film, enhancing the crystallization of perovskites and addressing the issue of 2 slow electron extraction. In addition, it can also resist the ingression of moisture, protect the interfaces from chemical erosion, and passivate the voids or pinholes generated in the holetransporting layer. As a result, we obtain an outstanding power conversion efficiency (PCE) of 20.8 % compared with 19.9 % by PCBM, accompanied by excellent stability under heat and simulated sunlight,. The PCE of unsealed devcies dropped by less than 10% in ambient air (40% RH) after 44 days at 65 ℃ and by 4% after 600 h under continuous full sun illumination and maximum power point tracking respectively.Hybrid organic-inorganic lead halide perovskite solar cells (PSCs) have emerged as a promising candidate for the next generation photovoltaic technology due to their low manufacturing cost and high performance. 1−6 Through judicious manipulation of perovskite morphology and improvement of interfacial properties, 2−6 PSCs have reached a certified power conversion efficiency (PCE) up to 22.1%. 7 Generally, the PSCs with the best performance employ a sandwich configuration, composed of a layer of TiO 2 electron selective contact, which is infiltrated by the intrinsic perovskite light harvester, followed by a layer of hole transport material (HTM) as p-type contact and a metal back contact. 8 Despite of these stunning advances, several challenges still remain before PSCs become a competitive commercial technology, one crucial issue being the device stability. 9−11 Uncontrolled film morphology associated with poor crystallity of the perovskites results in low efficiency and poor reproducibility of the device performance. 12 Previous studies have indicated that the degradation of PSCs is primarily governed by the ingress of atmospheric oxygen and water vapor into the film upon exposure to air, which in turn causes undesired reactions with the active materials. 13,14 Various methods have been tried to modify the morphology of perovskite films aiming to improve the stability, for example, poly(methyl methacrylate) (PMMA) was used as a template to control nucleation and crystal growth, resulting in considerable increase in both the device efficiency and stability when kept under 3 dry condition in the dark. 15 Other studies use additives like 1-methyl-3-(1H,1H,2H,2H-nonafluorohexyl)-imidazolium iodide, 16 or phenyl-C 61 -b...

The as-produced isomer mixture of the organic photovoltaic device acceptor material bis-[60]PCBM has been purified into its constituents by peak-recycling HPLC, and those individual isomers were characterised by UV-Vis absorption spectroscopy and cyclic voltammetry. A total of 18 isomers were purified from the mixture to a standard exceeding 99.5% with respect to other isomers. The HOMOs, LUMOs, and HOMO-LUMO gaps of the purified isomers vary from -5.673 to -5.444 eV, -3.901 to -3.729 eV, and 1.664 to 1.883 eV, respectively. We also find a correlation between HPLC retention time and the relative positions of the addends; in that generally the closer the addends are to each other the longer the retention time of the isomer, and vice versa.

There are only a few reported methods by which the size and morphology of organic single crystals for high-performance organic field-effect transistors (OFETs) or other devices can be controlled. Here, a facile solution-processed antisolvent vapor diffusion method was employed to grow millimeter-length C60 single crystal microwires directly in solution. The size of the microwires can be controllably varied via the C60 concentration and/or the choice of antisolvent. OFETs fabricated from the as-produced microwires exhibit mobilities as high as 2.30 cm2 V-1 s-1. A clear relationship between the crystal preparation conditions and device performance is revealed whereby it is observed that the lower the evaporation rate of antisolvent and/or the higher the C60 concentration, the higher the device performance. Photodetectors based on our microwires give a responsivity that is an order of magnitude higher than those grown by drop-casting methods. This study provides a facile method for the crystal engineering of size-tunable millimeter-length C60 single crystals, and revealed the important influences of the antisolvent on the C60 crystal size and the performance of devices based on them. We believe that our processing approach can be further exploited for a broad range of other organic semiconductors to achieve desirable single crystal size and morphology and thus obtain desirable OFETs and photodetector performance.

Organic semiconducting single crystals are ideal building blocks for organic field-effect transistors (OFETs) and organic photodetectors (OPDs) because they can potentially exhibit the best charge transport and photoelectric properties in organic materials. Nevertheless, it is usual for single-crystal OFETs to be built from one kind of organic material in which the dominant transport is either electron or hole; such OFETs showing unipolar charge transport. Furthermore, single-crystal OPDs present high performance only in restricted regions because of the limited absorption of one-component single crystals. In an ideal situation, devices which comprise both electron and hole transporting single crystals with complementary absorptions, like single-crystalline p-n heterojunctions (SCHJs), can permit broadband photo-response and ambipolar charge transport. In this paper, a solution-processing crystallization strategy to prepare an SCHJ composed of C 60 and 6,13bis(triisopropylsilylethynyl)pentacene (TIPS-PEN) was shown. These SCHJs demonstrated ambipolar charge transport characteristics in OFETs with a balanced performance of 2.9 cm 2 V −1 s −1 for electron mobility and 2.7 cm 2 V −1 s −1 for hole mobility. This demonstration is the first of single-crystal OFETs in which both electron and hole mobilities were over 2.5 cm 2 V −1 s −1 . OPDs fabricated upon as-prepared SCHJs exhibited highly-sensitive photo-conductive properties ranging from ultraviolet to visible and further to near-infrared regions as a result of complementary absorption between C 60 and TIPS-PEN; thereby attaining the photo-responsivities amongst the highest-reported values within the organic photodetectors. This work would provide valuable references for developing novel SCHJ systems to achieve significant progress in high-performance ambipolar OFETs and broadband OPDs. IntroductionRecently, continuous research attention has been drawn to organic field-effect transistors (OFETs) for lightweight and deformable electronic applications like photodetectors, 1 sensors, 2 displays, 3 and circuits. 4 Included in these, organic photodetectors (OPDs), which translate optical signals into electrical signals, occupy an essential position in optical interconnection techniques, light-wave communications,

[60]PCBM single crystals were prepared to understand their intrinsic photo-responsivity, stability, and charge transport properties.