Continuous illumination of the organometal trihalide perovskite (OTP) devices can cause the photovoltaic poling effect, termed light‐induced self‐poling (LISP), which improves the stabilized device ...efficiency significantly. The effect of LISP is comparable to the poling by an externally applied electric field, which can be explained by the redistribution of ions/vacancies within the OTP layers driven by a photovoltage‐induced additional electric field.
The manipulation of crystal orientation from the thermodynamic equilibrium states is desired in layered hybrid perovskite films to direct charge transport and enhance the perovskite devices ...performance. Here we report a templated growth mechanism of layered perovskites from 3D-like perovskites which can be a general design rule to align layered perovskites along the out-of-plane direction in films made by both spin-coating and scalable blading process. The method involves suppressing the nucleation of both layered and 3D perovskites inside the perovskite solution using additional ammonium halide salts, which forces the film formation starts from solution surface. The fast drying of solvent at liquid surface leaves 3D-like perovskites which surprisingly templates the growth of layered perovskites, enabled by the periodic corner-sharing octahedra networks on the surface of 3D-like perovskites. This discovery provides deep insights into the nucleation behavior of octahedra-array-based perovskite materials, representing a general strategy to manipulate the orientation of layered perovskites.
Intentional doping is the core of semiconductor technologies to tune electrical and optical properties of semiconductors for electronic devices, however, it has shown to be a grand challenge for ...halide perovskites. Here, we show that some metal ions, such as silver, strontium, cerium ions, which exist in the precursors of halide perovskites as impurities, can n-dope the surface of perovskites from being intrinsic to metallic. The low solubility of these ions in halide perovskite crystals excludes the metal impurities to perovskite surfaces, leaving the interior of perovskite crystals intrinsic. Computation shows these metal ions introduce many electronic states close to the conduction band minimum of perovskites and induce n-doping, which is in striking contrast to passivating ions such as potassium and rubidium ion. The discovery of metallic surface doping of perovskites enables new device and material designs that combine the intrinsic interior and heavily doped surface of perovskites.
Organic–inorganic halide perovskites are promising photodetector materials due to their strong absorption, large carrier mobility, and easily tunable bandgap. Up to now, perovskite photodetectors are ...mainly based on polycrystalline thin films, which have some undesired properties such as large defective grain boundaries hindering the further improvement of the detector performance. Here, perovskite thin‐single‐crystal (TSC) photodetectors are fabricated with a vertical p–i–n structure. Due to the absence of grain‐boundaries, the trap densities of TSCs are 10–100 folds lower than that of polycrystalline thin films. The photodetectors based on CH3NH3PbBr3 and CH3NH3PbI3 TSCs show low noise of 1–2 fA Hz−1/2, yielding a high specific detectivity of 1.5 × 1013 cm Hz1/2 W−1. The absence of grain boundaries reduces charge recombination and enables a linear response under strong light, superior to polycrystalline photodetectors. The CH3NH3PbBr3 photodetectors show a linear response to green light from 0.35 pW cm−2 to 2.1 W cm−2, corresponding to a linear dynamic range of 256 dB.
Photodetectors based on organic–inorganic halide perovskite thin single crystals (TSCs) are fabricated. Due to the absence of grain‐boundaries, very low trap densities, and small thickness (≈10 µm) of the TSCs, the TSC photodetectors with vertical p–i–n structure show low noise (1–2 fA Hz−1/2), high specific detectivity (≈1.5 × 1013 cm Hz1/2 W−1), and large linear‐dynamic‐range (256 dB).
The instability of hybrid perovskite materials due to water and moisture arises as one major challenge to be addressed before any practical application of the demonstrated high efficiency perovskite ...solar cells. Here we report a facile strategy that can simultaneously enhance the stability and efficiency of p-i-n planar heterojunction-structure perovskite devices. Crosslinkable silane molecules with hydrophobic functional groups are bonded onto fullerene to make the fullerene layer highly water-resistant. Methylammonium iodide is introduced in the fullerene layer for n-doping via anion-induced electron transfer, resulting in dramatically increased conductivity over 100-fold. With crosslinkable silane-functionalized and doped fullerene electron transport layer, the perovskite devices deliver an efficiency of 19.5% with a high fill factor of 80.6%. A crosslinked silane-modified fullerene layer also enhances the water and moisture stability of the non-sealed perovskite devices by retaining nearly 90% of their original efficiencies after 30 days' exposure in an ambient environment.
A self‐powered,solution‐processed perovskite photodetector with sub‐nanosecond response time is presented. Eliminating charge trapping and removing the constraints from the resistance–capacitance ...constant increases the response speed, which enables them to be applied in a homemade, time‐resolved photoluminescence system that successfully resolves the decay process of typical fluorescence and phosphorescent materials with a recombination lifetime from several nanoseconds to microseconds.
Carbon dots show potential in lighting and displays. However, only their fluorescence has been observed so far. Here we report the observation of phosphorescence from carbon dots in a polyvinyl ...alcohol matrix. The phosphorescence is attributed to C=O bonds on the surface of carbon dots and has a very long lifetime (~380 ms).
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