The efficiency of perovskite solar cells has increased to a certified value of 25.2% in the past 10 years, benefiting from the superior properties of metal halide perovskite materials. Compared with ...the widely investigated polycrystalline thin films, single crystal perovskites without grain boundaries have better optoelectronic properties, showing great potential for photovoltaics with higher efficiency and stability. Additionally, single crystal perovskite solar cells are a fantastic model system for further investigating the working principles related to the surface and grain boundaries of perovskite materials. Unfortunately, only a handful of groups have participated in the development of single crystal perovskite solar cells; thus, the development of this area lags far behind that of its polycrystalline counterpart. Therefore, a review paper that discusses the recent developments and challenges of single crystal perovskite solar cells is urgently required to provide guidelines for this emerging field. In this progress report, the optical and electrical properties of single crystal and polycrystalline perovskite thin films are compared, followed by the recent developments in the growth of single crystal perovskite thin films and the photovoltaic applications of this material. Finally, the challenges and perspectives of single crystal perovskite solar cells are discussed in detail.
Their superior optoelectronic properties and stability endow organic–inorganic halide perovskite single crystals great potential for high‐efficiency and stable photovoltaics. This progress report summarizes recent exciting developments and future perspectives for perovskite single crystal solar cells, which may attract more attention and provide guidelines for further development in this emerging field.
Organic cocrystals possess valuable properties owing to the synergistic effect of the individual components. However, the growth of molecular cocrystals is still in its primary stage. Here we develop ...a microspacing in-air sublimation method to grow organic cocrystals, and furthermore to realize morphology control on them, which is essential for structure-property relations. A series of polycyclic aromatic hydrocarbon (PAH)‒1,2,4,5-tetracyanobenzene (TCNB) complexes cocrystals are grown directly on the substrate, with the morphology tunable from 1D needle-like to 2D plate-like on demand. Spatially resolved photoluminescence spectra analyses on different cocrystals display morphology dependent and anisotropic optical waveguiding properties. In situ observation and energy calculations of the crystallization processes reveal the formation mechanism being from a competition between growth kinetics-defined crystal habit and the thermodynamics driving force. This growth technique may serve the future demand for tunable morphology organic cocrystals in different functional applications.
In strongly correlated materials, lattice, charge, spin and orbital degrees of freedom interact with each other, leading to emergent physical properties such as superconductivity, colossal magnetic ...resistance and metal-insulator transition. Quasi-2D square planar nickelates, R
n
+1
Ni
n
O
2
n
+2
(R = rare earth,
n
= 2, 3...∞), are of significant interest and long sought for cuprate analogues due to the 3d
9
electronic configuration of Ni
+
, the same as the active ion Cu
2+
in the high-
T
c
superconducting cuprates. The field has attracted intense attention since 2019 due to the discovery of superconductivity in thin films of Nd
0.8
Sr
0.2
NiO
2
, although no superconductivity has been reported in bulk polycrystalline powders. Herein, we review the synthesis of polycrystalline powders of quasi-2D square planar nickelates through topotactic reduction of parent compounds that are synthesized
via
solid state reaction, precursor method, high pressure floating zone method and high-pressure flux method. We emphasize single crystal preparation using the high-pressure floating zone techniques. We discuss their crystal structure and physical properties including resistivity, magnetic susceptibility and heat capacity. We highlight the cuprate-like physics, including charge/spin stripes and large orbital polarization, identified in single crystals of R
4
Ni
3
O
8
(R = La and Pr) combining synchrotron X-ray/neutron single crystal diffraction and density functional theory calculations. Furthermore, the challenges and possible research directions of this fast-moving field in the future are briefly discussed.
Quasi-2D square planar nickelates exhibit key ingredients of high-
T
c
superconducting cuprates. Whether bulk samples are superconducting remains an open question, single crystals are ideal platforms for addressing such fundamental questions.
1,4‐butanediamine (BEA) is incorporated into FASnI3 (FA=formamidinium) to develop a series of lead‐free low‐dimensional Dion–Jacobson‐phase perovskites, (BEA)FAn−1SnnI3n+1. The broadness of the ...(BEA)FA2Sn3I10 band gap appears to be influenced by the structural distortion owing to high symmetry. The introduction of BEA ligand stabilizes the low‐dimensional perovskite structure (formation energy ca. 106 j mol−1), which inhibits the oxidation of Sn2+. The compact (BEA)FA2Sn3I10 dominated film enables a weakened carrier localization mechanism with a charge transfer time of only 0.36 ps among the quantum wells, resulting in a carrier diffusion length over 450 nm for electrons and 340 nm for holes, respectively. Solar cell fabrication with (BEA)FA2Sn3I10 delivers a power conversion efficiency (PCE) of 6.43 % with negligible hysteresis. The devices can retain over 90 % of their initial PCE after 1000 h without encapsulation under N2 environment.
A low‐dimensional DJ: A Dion–Jacobson‐phase lead‐free perovskite, (BEA)FAn−1SnnI3n+1 (BEA=1,4‐butanediamine, FA=formamidinium), is used to fabricate perovskite solar cells. The representative (BEA)FA2Sn3I10 perovskite exhibits excellent optical absorption and carrier transport, resulting in a record power conversion efficiency of 6.43 %.
Transition-metal oxides with special optoelectronic properties have received extensive attention and have been the subject of research studies in recent decades. In particular, tellurite ...molybdate/tungstate materials have exhibited multifunctional optoelectronic properties, which attracts considerable academic interest. Under the second-order Jahn-Teller effect, compounds with non-centrosymmetric structures including
d
0
transition metals and cations with lone-pair electrons have been a hotspot in materials research. In recent years, a series of tellurite molybdate/tungstate crystals have been grown successfully. Research on structure-property relationships, physical properties and electric/optical devices especially in the mid-infrared range has developed rapidly. In this work, recent advances in tellurite molybdate/tungstate crystals are reviewed.
In this work, recent advances in tellurite molybdate/tungstate crystals have been systematically reviewed, including crystal growth, research of physical properties, theoretical analysis, and some electric/optical devices.
The relatively low resistivity and severe ion migration in CsPbBr3 significantly degrade the performance of X‐ray detectors due to their high detection limit and current drift. The electrical ...properties and X‐ray detection performances of CsPbBr3−nIn single crystals are investigated by doping the iodine atoms into the melt‐grown CsPbBr3. The resistivity of CsPbBr3−nIn single crystals increases from 3.6 × 109 (CsPbBr3) to 2.2 × 1011 (CsPbBr2I) Ω cm, restraining the leak current and decreasing the detection limit of the detector. Additionally, CsPbBr3−nIn single crystals exhibit stable dark currents, arising from their high ion migration activation energy. A record sensitivity of 6.3 × 104 µC Gy−1 cm−2 (CsPbBr2.9I0.1) and a low detection limit of 54 nGy s−1 (CsPbBr2I) are achieved by CsPbBr3−nIn single crystals for the 120 keV hard X‐ray detection under a 5000 V cm−1 electrical field. The CsPbBr2.9I0.1 detector shows a stable current response with a dark current density of 0.58 µA cm−2 for 30 days and clear imaging for 120 keV Xrays at ambient conditions. The effective iodine atom doping strategy makes the CsPbBr3−nIn single crystals promising for reproducible high‐energy hard X‐ray imaging systems.
The CsPbBr2.9I0.1 (I0.1) detector shows the no‐drift dark current and a record sensitivity of 6.3 × 104 µC Gy−1 cm−2 for 120 keV high‐energy hard X‐rays under a 5000 V cm−1 electric field due to the suppressed ion migration. Moreover, clear X‐ray imaging of the “pork rib” is realized using the I0.1 planar array detector under 120 keV X‐ray irradiation.
Nanocatalysts based on Fenton or Fenton‐like reactions for amplification of intracellular oxidative stress has become a frontier research area of tumor precise therapy. However, the major ...translational challenges are low catalytic efficiency, poor biocompatibility, and even potential toxicities. Here, a Ti‐based material with excellent biocompatibility is proposed for cancer treatment. The nonoxidized MXene‐Ti3C2Tx quantum dots (NMQDs‐Ti3C2Tx) are successfully prepared by a self‐designed microexplosion method. Surprisingly, it has an apparent inhibitory and killing effect on cancer cells, and excellent biocompatibility with normal cells. Moreover, the suppression rate of NMQDs‐Ti3C2Tx on xenograft tumor models can reach 91.9% without damaging normal tissues. Mechanistically, the Ti3+ of NMQDs‐Ti3C2Tx can react with H2O2 in the tumor microenvironment and high‐efficiently produce excessive toxic hydroxyl radicals to increase tumor microvascular permeability to synergistically kill cancer cells. This work should pave the way for tumor catalytic therapy applications of Ti‐based material as a promising and safer route.
For nanocatalytic treatment of tumors, a safer strategy is proposed: using titanium‐based materials with good biocompatibility for tumor treatment. The prepared nonoxidized MXene‐Ti3C2Tx quantum dots show satisfactory antitumor effect, proving the feasibility of this strategy. Although inoculated tumor cells are the fastest‐growing HeLa cells, the tumor suppression rate is 91.9%, without affecting the health of mice.
Singlet–triplet conversion in organic light‐emitting materials introduces non‐emissive (dark) and long‐lived triplet states, which represents a significant challenge in constraining the optical ...properties. There have been considerable attempts at separating singlets and triplets in long‐chain polymers, scavenging triplets, and quenching triplets with heavy metals; nonetheless, such triplet‐induced loss cannot be fully eliminated. Herein, a new strategy of crafting a periodic molecular barrier into the π‐conjugated matrices of organic aromatic fluorophores is reported. The molecular barriers effectively block the singlet‐to‐triplet pathway, resulting in near‐unity photoluminescence quantum efficiency (PLQE) of the organic fluorophores. The transient optical spectroscopy measurements confirm the absence of the triplet absorption. These studies provide a general approach to preventing the formation of dark triplet states in organic semiconductors and bring new opportunities for the development of advanced organic optics and photonics.
Reaching unity: Organic cocrystals show the absence of triplet states of the conjugated aromatic fluorophores (anthracene and coronene) upon photoexcitation and display unity photoluminescence quantum efficiency. Periodic molecular barriers, octafluoronaphthalene molecules, prevent the singlet excitons from accessing triplet states. This provides a novel and general strategy to eliminate photobleaching due to triplet loss in organic semiconductors.
Self‐powered perovskite X‐ray detectors have drawn increasing attention due to the merits of low noise, low power consumption as well as high portability and adaptability. However, the active layer ...thickness is usually compromised by the small carrier diffusion length, which leads to inefficient X‐ray attenuation and hence low sensitivity of the detectors. Herein, self‐powered and highly sensitive single‐crystal perovskite X‐ray detectors are achieved by finely controlling the crystal thickness and optimizing their carrier transport properties. Perovskite single crystals with thickness of around 800 µm are grown by a two‐step crystal growth process to realize the full attenuation of hard X‐ray with the energy of 80 keV. And the incorporation of formamidinium (FA) (FA = CH(NH2)2+) cation into methylammonium lead triiodide (MAPbI3) (MA = CH3NH3+) increases the mobility‐lifetime (µτ) product of the single crystals by nearly one order of magnitude, leading to a record X‐ray detection sensitivity of 8.7 × 104 µC Gyair−1 cm−2 under zero bias. Moreover, the eliminated external bias and reduced trap density weaken the field‐driven ion migration effect, and therefore result in a low detection limit of 27.7 nGy s−1. This work represents an effective way to achieve self‐powered perovskite X‐ray detectors with both high sensitivity and low detection limit.
Self‐powered and highly sensitive perovskite X‐ray detectors are achieved by fine control of crystal thickness and optimization of carrier transport properties. High sensitivity of 8 × 104 µC Gyair–1 cm–2 and low detection limit of 27.7 nGyair s−1 are obtained without external bias, which may broaden the application of X‐ray detectors when portability and adaptability are required.
PDF
