Abstract
All-inorganic perovskites have a special place in halide perovskite family because of their potential for better stability. However, the representative cesium lead iodide (CsPbI
3
) is ...metastable and spontaneously converts to the non-perovskite structure at room temperature. Here, we demonstrate that what appears to be all-inorganic CsPbI
3
stabilized in its perovskite form using the purported intermediate known as hydrogen lead iodide (HPbI
3
) is, in fact, the hybrid perovskite cesium dimethylammonium lead iodide (Cs
1−
x
DMA
x
PbI
3
,
x
= 0.2 to 0.5). Thus, many of the reported all-inorganic perovskites are actually still hybrid organic-inorganic perovskites, as strongly evidenced by a wide battery of experimental techniques presented here. Solar cells based on the representative composition Cs
0.7
DMA
0.3
PbI
3
can achieve an average power conversion efficiency of 9.27 ± 1.28% (max 12.62%). These results provide an alternative angle to look at previous results pertaining all-inorganic CsPbI
3
while the DMA cation is now revealed as an alternative A site cation.
Halide perovskite semiconductors are poised to revitalize the field of ionizing radiation detection as they have done to solar photovoltaics. We show that all-inorganic perovskite CsPbBr3 devices ...resolve 137Cs 662-keV γ-rays with 1.4% energy resolution, as well as other X- and γ-rays with energies ranging from tens of keV to over 1 MeV in ambipolar sensing and unipolar hole-only sensing modes with crystal volumes of 6.65 mm3 and 297 mm3, respectively. We report the scale-up of CsPbBr3 ingots to up to 1.5 inches in diameter with an excellent hole mobility–lifetime product of 8 × 10−3 cm2 V−1 and a long hole lifetime of up to 296 μs. CsPbBr3 detectors demonstrate a wide temperature region from ~2 °C to ~70 °C for stable operation. Detectors protected with suitable encapsulants show a uniform response for over 18 months. Consequently, we identify perovskite CsPbBr3 semiconductor as an exceptional candidate for new-generation high-energy γ-ray detection.Energy resolution of high-energy photon detectors is desired for applications ranging from biomedical imaging to homeland security. In this work, perovskite-based γ-ray detection with 1.4% energy resolution is demonstrated.
The molecular building block approach was employed effectively to construct a series of novel isoreticular, highly porous and stable, aluminum-based metal–organic frameworks with soc topology. From ...this platform, three compounds were experimentally isolated and fully characterized: namely, the parent Al-soc-MOF-1 and its naphthalene and anthracene analogues. Al-soc-MOF-1 exhibits outstanding gravimetric methane uptake (total and working capacity). It is shown experimentally, for the first time, that the Al-soc-MOF platform can address the challenging Department of Energy dual target of 0.5 g/g (gravimetric) and 264 cm3 (STP)/cm3 (volumetric) methane storage. Furthermore, Al-soc-MOF exhibited the highest total gravimetric and volumetric uptake for carbon dioxide and the utmost total and deliverable uptake for oxygen at relatively high pressures among all microporous MOFs. In order to correlate the MOF pore structure and functionality to the gas storage properties, to better understand the structure–property relationship, we performed a molecular simulation study and evaluated the methane storage performance of the Al-soc-MOF platform using diverse organic linkers. It was found that shortening the parent Al-soc-MOF-1 linker resulted in a noticeable enhancement in the working volumetric capacity at specific temperatures and pressures with amply conserved gravimetric uptake/working capacity. In contrast, further expansion of the organic linker (branches and/or core) led to isostructural Al-soc-MOFs with enhanced gravimetric uptake but noticeably lower volumetric capacity. The collective experimental and simulation studies indicated that the parent Al-soc-MOF-1 exhibits the best compromise between the volumetric and gravimetric total and working uptakes under a wide range of pressure and temperature conditions.
The unique hybrid nature of 2D Ruddlesden–Popper (R–P) perovskites has bestowed upon them not only tunability of their electronic properties but also high-performance electronic devices with improved ...environmental stability as compared to their 3D analogs. However, there is limited information about their inherent heat, light, and air stability and how different parameters such as the inorganic layer number and length of organic spacer molecule affect stability. To gain deeper understanding on the matter we have expanded the family of 2D R–P perovskites, by utilizing pentylamine (PA)2(MA) n−1Pb n I3n+1 (n = 1–5, PA = CH3(CH2)4NH3 +, C5) and hexylamine (HA)2(MA) n−1Pb n I3n+1 (n = 1–4, HA = CH3(CH2)5NH3 +, C6) as the organic spacer molecules between the inorganic slabs, creating two new series of layered materials, for up to n = 5 and 4 layers, respectively. The resulting compounds were extensively characterized through a combination of physical and spectroscopic methods, including single crystal X-ray analysis. High resolution powder X-ray diffraction studies using synchrotron radiation shed light for the first time to the phase transitions of the higher layer 2D R–P perovskites. The increase in the length of the organic spacer molecules did not affect their optical properties; however, it has a pronounced effect on the air, heat, and light stability of the fabricated thin films. An extensive study of heat, light, and air stability with and without encapsulation revealed that specific compounds can be air stable (relative humidity (RH) = 20–80% ± 5%) for more than 450 days, while heat and light stability in air can be exponentially increased by encapsulating the corresponding films. Evaluation of the out-of-plane mechanical properties of the corresponding materials showed that their soft and flexible nature can be compared to current commercially available polymer substrates (e.g., PMMA), rendering them suitable for fabricating flexible and wearable electronic devices.
The advent of the two-dimensional (2D) family of halide perovskites and their demonstration in 2D/three-dimensional (3D) hierarchical film structures broke new ground toward high device performance ...and good stability. The 2D Dion–Jacobson (DJ) phase halide perovskites are especially attractive in solar cells because of their superior charge transport properties. Here, we report on 2D DJ phase perovskites using a 3-(aminomethyl)piperidinium (3AMP) organic spacer for the fabrication of mixed Pb/Sn-based perovskites, exhibiting a narrow bandgap of 1.27 eV and a long carrier lifetime of 657.7 ns. Consequently, solar cells employing mixed 2D DJ 3AMP-based and 3D MA0.5FA0.5Pb0.5Sn0.5I3 (MA = methylammonium, FA = formamidinium) perovskite composites as light absorbers achieve enhanced efficiency and stability, giving a power conversion efficiency of 20.09% with a high open-circuit voltage of 0.88 V, a fill factor of 79.74%, and a short-circuit current density of 28.63 mA cm–2. The results provide an effective strategy to improve the performance of single-junction narrow-bandgap solar cells and, potentially, to give a highly efficient alternative to bottom solar cells in tandem devices.
Developing dopant-free hole transporting layers (HTLs) is critical in achieving high-performance and robust state-of-the-art perovskite photovoltaics, especially for the air-sensitive tin-based ...perovskite systems. The commonly used HTLs require hygroscopic dopants and additives for optimal performance, which adds extra cost to manufacturing and limits long-term device stability. Here we demonstrate the use of a novel tetrakis-triphenylamine (TPE) small molecule prepared by a facile synthetic route as a superior dopant-free HTL for lead-free tin-based perovskite solar cells. The best-performing tin iodide perovskite cells employing the novel mixed-cation ethylenediammonium/formamidinium with the dopant-free TPE HTL achieve a power conversion efficiency as high as 7.23%, ascribed to the HTL’s suitable band alignment and excellent hole extraction/collection properties. This efficiency is one of the highest reported so far for tin halide perovskite systems, highlighting potential application of TPE HTL material in low-cost high-performance tin-based perovskite solar cells.
The halide perovskite Ruddlesden–Popper (RP) phases are a homologous layered subclass of solution-processable semiconductors that have aroused great attention, especially for developing long-term ...solar photovoltaics. They are defined as (A′)2(A) n−1Pb n X3n+1 (A′ = spacer cation, A = cage cation, and X = halide anion). The orientation control of low-temperature self-assembled thin films is a fundamental issue associated with the ability to control the charge carrier transport perpendicular to the substrate. Here we report new chemical derivatives designed from a molecular perspective using a novel spacer cation 3-phenyl-2-propenammonium (PPA) with conjugated backbone as a low-temperature strategy to assemble more efficient solar cells. First, we solved and refined the crystal structures of single crystals with the general formula (PPA)2(FA0.5MA0.5) n−1Pb n I3n+1 (n = 2 and 3, space group C2) using X-ray diffraction and then used the mixed halide (PPA)2(Cs0.05(FA0.88MA0.12)0.95) n−1Pb n (I0.88Br0.12)3n+1 analogues to achieve more efficient devices. While forming the RP phases, multiple hydrogen bonds between PPA and inorganic octahedra reinforce the layered structure. For films we observe that as the targeted layer thickness index increases from n = 2 to n = 4, a less horizontal preferred orientation of the inorganic layers is progressively realized along with an increased presence of high-n or 3D phases, with an improved flow of free charge carriers and vertical to substrate conductivity. Accordingly, we achieve an efficiency of 14.76% for planar p–i–n solar cells using PPA-RP perovskites, which retain 93.8 ± 0.25% efficiency with encapsulation after 600 h at 85 °C and 85% humidity (ISOS-D-3).
Hybrid layered halide perovskites have achieved impressive performance in optoelectronics. New structural types in the two-dimensional (2D) halide system such as the Dion–Jacobson phases have ...attracted wide research attention due to the short interlayer distance and unique layer orientation that facilitate better charge-transport and higher stability in optoelectronic devices. Here, we report the first solid solution series incorporating both A and A’ cations in the 2D Dion–Jacobson family, with the general formula (A’)(A)Pb2Br7 ((A’ = 3-(aminomethyl)piperidinium (3AMP) and 4-(aminomethyl)piperidinium) (4AMP); A = methylammonium (MA) and formamidinium (FA)). Mixing the spacing A’ cations and perovskitizer A cations generates the new (3AMP) a (4AMP)1–a (FA) b (MA)1–b Pb2Br7 perovskites. The crystallographically refined crystal structures using single-crystal X-ray diffraction data reveal that the distortion of the inorganic framework is heavily influenced by the degree of A’ and A alloying. A rising fraction of 4AMP in the structure, decreases the Pb–Br–Pb angles, making the framework more distorted. On the contrary, higher FA fractions increase the Pb–Br–Pb angles. This structural evolution fine-tunes the optical properties where the larger the Pb–Br–Pb angle, the narrower the band gap. The photoluminescence emission energy mirrors this trend. Raman spectroscopy reveals a highly dynamical lattice similar to MAPbBr3 and consistent with the local distortion environment of the Pb2Br7 framework. Density functional theory (DFT) calculations of the electronic structures reveal the same trend as the experimental results where (3AMP)(FA)Pb2Br7 has the smallest band gap while (4AMP)(MA)Pb2Br7 has the largest band gap. The structural effects from solely the organic cations in the 2D system highlight the importance of understanding the high sensitivity of the optoelectronic properties on the structural tuning in this broad class of materials.
The introduction of large-volume amines (LVAs) in Sn-based perovskite films has been shown to lead to promising power conversion efficiency (PCE) in Pb-free perovskite solar cells (PSCs). However, ...the LVAs adopted so far (e.g., phenylethylammonium PEA and butylammonium BA) are insulating and could impede charge extraction within the perovskite film. Herein, a conjugated LVA, 3-phenyl-2-propen-1-amine (PPA), is introduced in formamidinium tin iodide (FASnI3) perovskite. Our results show that the incorporation of PPA results in enlarged grain sizes, reduced trap density, preferential orientation, efficient charge extraction, and enhanced structural stability of FASnI3 film. These positive effects help in achieving efficient PSCs with a PCE as high as 9.61% with negligible hysteresis and outstanding stability (remains 92% of its initial PCE value after 1,440 h). Furthermore, the presence of PPA enables a self-healing action of PSCs. Most importantly, we report large-area (1 × 1 cm2) Sn-based PSCs achieving PCE of 7.08%.
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•Conjugated cation is incorporated as an additive in tin perovskite for the first time•Film showing oriented grains with enlarged size and enhanced charge extraction•Solar cells with PCE of 9.61% on 0.09 cm2 and 7.08% on 1 cm2 are achieved•Robust device stability with self-healing behavior can be enabled
For ecofriendly concerns, Sn-based PSCs have been extensively studied and made inspiring progress during the past few years. Recently, the introduction of large-volume amines (LVAs) (e.g., phenylethylammonium PEA and butylammonium BA) have shown their promise in enhancing the performance of FASnI3-based PSCs. However, the insulating nature of these LVAs sets limitations on the charge extraction of the film. Herein, a conjugated LVA, 3-phenyl-2-propen-1-amine (PPA), is introduced aiming at promoting charge extraction within FASnI3 film. The presence of PPA is found to enlarge the grain size, passivate the grains, and induce the orientation of the film. These merits of PPA deliver PSCs with PCE of 9.61% on 0.09 cm2 and 7.08% on 1 cm2. Moreover, PPA-based PSCs exhibit robust stability and self-healing behavior. This work sheds critical lights on improving the quality of perovskite film by molecular design of organic cations and highlights the promise of Pb-free PSCs.
A conjugated large-volume cation is adopted as an additive to modify FASnI3 film with much improved film quality. Lead-free PSC devices with PCE of 9.61% on 0.09 cm2 and 7.08% on 1 cm2 can be achieved. The PSC devices also show robust stability with self-healing ability. This work addresses the promise of Sn-based PSCs and takes a big step forward in the field of ecofriendly lead-free photovoltaic devices.
Understanding and tailoring the physical behaviour of halide perovskites under practical environments is critical for designing efficient and durable optoelectronic devices. Here, we report that ...continuous light illumination leads to >1% contraction in the out-of-plane direction in two-dimensional hybrid perovskites, which is reversible and strongly dependent on the specific superlattice packing. X-ray photoelectron spectroscopy measurements show that constant light illumination results in the accumulation of positive charges in the terminal iodine atoms, thereby enhancing the bonding character of inter-slab I-I interactions across the organic barrier and activating out-of-plane contraction. Correlated charge transport, structural and photovoltaic measurements confirm that the onset of the light-induced contraction is synchronized to a threefold increase in carrier mobility and conductivity, which is consistent with an increase in the electronic band dispersion predicted by first-principles calculations. Flux-dependent space-charge-limited current measurement reveals that light-induced interlayer contraction activates interlayer charge transport. The enhanced charge transport boosts the photovoltaic efficiency of two-dimensional perovskite solar cells up to 18.3% by increasing the device's fill factor and open-circuit voltage.
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