Although the room-temperature phosphorescence (RTP) organic material is a long-studied topic and has become especially popular in the recent decade, all-round players with qualified long-lived RTP lifetimes to fulfill the...

Doped organic crystals possess wide application potential in the fields of scintillators and maser gain medium. However, the growth of doped organic single crystals with bulk size and high quality is still a big challenge due to the well-known poor crystallization capacity for organic materials. Here we report a thermal field-elevating technique to realize optimized growth conditions for organic crystals, where a pentacene-doped p-terphenyl single crystal with a size of Φ18 mm × 80 mm is obtained. Crystal quality and doping concentration effect on the optical properties of the crystalline wafers are investigated. The results show that p-terphenyl single crystal as an ordered matrix not only separates the guest molecules from one another to prevent quenching, but also constructs a Shpolskii-type host as an orienting medium to increase the interaction of pentacene with light. Moreover, a slightly reducing growth atmosphere is found to generate longer excitation lifetimes and a larger magnetic susceptibility of the grown doped crystal, which may be favorable for the spin-related physical process occurring in the excited state.

Three-dimensional perovskite AMX3 has great potential in photoelectric applications, but the poor stability is a major problem that restricts its practical application. The emergence of lower dimensional perovskite solves this problem. Here, we have synthesized a group of novel low-dimensional perovskites with diverse structures. Different amino acids were incorporated in the perovskite cage. The formulas of the compounds are (A′) m PbI m+2 (A′ = COOH­(CH2) n NH2, n = 1, 3, 5, 7, 9). These families of materials demonstrate structure-related stability, tunable bandgap, and different photoluminescence. Single-crystal X-ray diffraction indicated that the five materials employ different structure types varying from edge-sharing structures to face- and corner-sharing Pb/I structures by adjusting the number of C atoms in organic cations, and the level of [PbI6]4– octahedral distortion was also identified. The film prepared using these materials with longer carbon chains (n = 5, 7, 9) showed better stability, and they did not decompose within one year at 75% RH, 40 °C. The bifunctional organic ions containing carboxyl groups as spacer cations will form additional hydrogen bonding between perovskite layers, resulting in higher stability of the material. The band gaps of these materials vary from 2.19 to 2.6 eV depending on the octahedral connection mode and [PbI6]4– octahedral distortion level, density functional theory calculations (DFT) are consistent with our experimental trends and suggest that the face-sharing structure has the maximum band gap due to its flatter electron band structure. Bright green fluorescence was observed in (COOH­(CH2)7NH3)2PbI4 and (COOH­(CH2)9NH3)2PbI4 when excited by 365 nm UV light. A thorough comprehension of the structure–property relationships is of great significance for further practical applications of perovskites.

The production of single-crystalline organic thin films on a large scale is challenging but imperative for industrial applications of organic electrics. This work improves a vapor-based method on the basis of our recently invented microspacing in-air sublimation (MAS) to achieve wafer-scale uniform single-crystalline organic films. The method alters the wettability of both the bottom and top substrates in MAS. By virtue of the vapor-to-melt-to-crystal process and the unique genetic relationship between the morphology of source materials and that of the grown crystals, wettability control on the one hand promotes the dispersion of the molten source materials and on the other hand drives the liquid crystal phase on the top substrate to form uniform single-crystalline films over the whole substrate. Using 2,7-dioctyl[1]­benzothieno­[3,2-b]­[1]­benzothiophene (C8-BTBT) as an example, centimeter-sized crystalline films with pure orientations are achieved. Transistor arrays fabricated on the crystalline films exhibit high yield and uniform performance with an average mobility of 3.91 cm2 V–1 s–1. This method provides an opportunity to realize vapor-grown single-crystalline films but not random and discrete single crystals via physical vapor transport nor the amorphous/polycrystalline films via vacuum deposition, which may be a step toward future commercialization of organic electronics.

Metal halide perovskite single crystals have become emerging candidates for photovoltaic applications due to their better optoelectronic properties and higher stability than their polycrystalline thin-film counterparts. However, in contrast to the rapid enhancement of power conversion efficiency (PCE), the operational stability of single-crystal perovskite solar cells (PSCs) remains far lagging behind. Herein, it is discovered that widely investigated 20 μm-thick single-crystal PSCs show poor operational stability, which is assigned to low crystal quality of these thin single crystals. Subsequently, the crystal quality of formamidinium0.55methylammonium0.45 lead triiodide (FA0.55MA0.45PbI3) thin single crystals are optimized by adjusting the ion diffusion velocity in confined space, leading to lower trap density, larger ion migration activation energy, and reduced light-induced degradation of material properties. As a result, stable single-crystal PSCs with no efficiency degradation after 330 h of continuous operation at the maximum power point under 1 sun illumination are achieved. Moreover, thickness-dependent device efficiency discloses an ultralong carrier transport length of 200 μm in FA0.55MA0.45PbI3 thin single crystals, which is instructive for developing lateral-structure solar cells.