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Three-dimensional/low-dimensional perovskite solar cells afford improved efficiency and stability. The design of low-dimensional capping materials is constrained to tuning the A-site organic cation, as Pb2+ and Sn2+ are the only options for the metal cation. Here we unlock access to a library of low-dimensional capping materials with metal cations beyond Pb2+/Sn2+ by processing a full precursor solution containing both metal and ammonium halides. This enables easier synthetic control of the low-dimensional capping layer and greater versatility for low-dimensional interface engineering. We demonstrate that a zero-dimensional zinc-based halogenometallate (PEA2ZnX4; PEA = phenethylammonium, X = Cl/I) induces more robust surface passivation and stronger n–N isotype three-dimensional/low-dimensional heterojunctions than its lead-based counterpart. We exhibit p–i–n solar cells with 24.1% efficiency (certified 23.25%). Our cells maintain 94.5% initial efficiency after >1,000 h of operation at the maximum power point. Our findings expand the material library for low-dimensional interface engineering and stabilization of highly efficient three-dimensional/low-dimensional perovskite solar cells. Ministry of Education (MOE) National Research Foundation (NRF) Submitted/Accepted version This work is supported by the Ministry of Singapore under its AcRF Tier 1 (Project RG6/21 (2021-T1-001-072) to Y.M.L.) and Tier 2 grants (MOE2019-T2-1-006 to T.C.S., MOE2019-T2-1-085 to Y.M.L. and MOE-T2EP50120-0004 to T.C.S.), and the National Research Foundation (NRF) Singapore under its NRF Investigatorship (NRF-NRFI2018-04 to T.C.S.).

Azole and azine heteroarenes were directly alkylated by alkanes, ethers, or carbamates using PhC(O)O2tBu under LED irradiation. 9,10-Dichloroanthrocene acted as an organic photocatalyst and transferred its excitation energy to PhC(O)O2tBu via exciplex formation.

Carrier diffusion and surface recombination are key processes influencing the performance of conventional semiconductor devices. However, the interplay of photon recycling together with these processes in halide perovskites obfuscates our understanding. Herein, we discern these inherent processes in a thin FAPbBr3 perovskite single crystal (PSC) utilizing a unique transient reflectance technique that allows accurate diffusion modeling with clear boundary conditions. Temperature-dependent measurements reveal the coexistence of shallow and deep traps at the surface. The inverse quadratic dependence of temperature on carrier mobility μ suggests an underlying scattering mechanism arising from the anharmonic deformation of the PbBr6 cage. Our findings ascertain the fundamental limits of the intrinsic surface recombination velocity (S) and carrier diffusion coefficient (D) in PSC samples. Importantly, these insights will help resolve the ongoing debate and clarify the ambiguity surrounding the contributions of photon recycling and carrier diffusion in perovskite optoelectronics. Ministry of Education (MOE) National Research Foundation (NRF) Submitted/Accepted version This research/project is supported by the Ministry of Education under its AcRF Tier 2 grants (MOE2019-T2-1-006, MOE2019-T2-1-097 and MOE-T2EP50120-0004); and the National Research Foundation (NRF) Singapore under its NRF Investigatorship (NRF-NRFI-2018-04).

Background COVID-19 is the first global pandemic in more than 100 years, and at its onset, the effects were largely unknown. Immunocompromised patients, including IBD, were presumed to have higher risk. Aims We hypothesized patients with IBD would have higher-than-baseline anxiety, high perceived vulnerability and significant lifestyle impacts as a result of the pandemic. We sought to assess the impact of these changes on disease and management. Methods A cross-sectional study of patients with Crohn’s disease, ulcerative colitis and IBD-unspecified was conducted. Patients were invited to participate by email in an IRB-approved brief, voluntary survey. Survey questions focused on disease characteristics, healthcare access and self-reported psychological well-being. Results Responses from 492 (CD = 337, UC = 141,IC = 14) patients were included in the analysis. The majority of patients with IBD had increased anxiety since the pandemic, which correlated with an increase in GI symptoms. This risk of symptoms was mitigated by communication with their provider. Many patients had lifestyle changes including requesting time off work due to perceived vulnerability and changes in eating habits. Conclusions Our findings support an increase in illness-associated anxiety and perceived vulnerability among patients with IBD during the COVID-19 pandemic. Open communication with providers is important to maintain adequate control of disease and reduce symptoms of flares triggered by ongoing stress. Supplementary Information The online version contains supplementary material available at 10.1007/s10620-021-07095-y.

Slow hot carrier cooling in halide perovskites holds the key to the development of hot carrier (HC) perovskite solar cells. For accurate modeling and pragmatic design of HC materials and devices, it is essential that HC temperatures are reliably determined. A common approach involves fitting the high-energy tail of the main photobleaching peak in a transient absorption spectrum with a Maxwell-Boltzmann distribution. However, this approach is problematic because of complications from the overlap of several photophysical phenomena and a lack of consensus in the community on the fitting procedures. Herein, we propose a simple approach that circumvents these challenges. Through tracking the broadband spectral evolution and accounting for bandgap renormalization and spectral line width broadening effects, our method extracts not only accurate and consistent carrier temperatures but also other important parameters such as the quasi-Fermi levels, bandgap renormalization constant, etc. Establishing a reliable method for the carrier temperature determination is a step forward in the study of HCs for next-generation perovskite optoelectronics. NRF (Natl Research Foundation, S’pore) MOE (Min. of Education, S’pore) Accepted version

Multiquantum-well (MQW) perovskite is one of the forerunners in high-efficiency perovskite LED (PeLEDs) research. Despite the rapid inroads, PeLEDs suffer from the pertinent issue of efficiency decrease with increasing brightness, commonly known as "efficiency roll-off". The underlying mechanisms are presently an open question. Herein, we explicate the E-field effects on the exciton states in the archetypal MQW perovskite (C6H5C2H4NH3)2PbI4, or PEPI, in a device-like architecture using field-assisted transient spectroscopy and theoretical modeling. The applied E-field results in a complex interplay of spectral blueshifts and enhancement/quenching of the different exciton modes. The former originates from the DC Stark shift, while the latter is attributed to the E-field modulation of the transfer rates between bright/dark exciton modes. Importantly, our findings uncover crucial insights into the photophysical processes under E-field modulation contributing to efficiency roll-off in MQW PeLEDs. Electrical modulation of exciton properties presents exciting possibilities for signal processing devices. Ministry of Education (MOE) National Research Foundation (NRF) Submitted/Accepted version Q.Z. is supported by the Singapore Ministry of Education under its AcRF Tier 2 Grant MOE2019-T2-2-2-066. T.K., K.D., and T.C.H.L. are supported by the AcRF Tier 2 Grant MOE2019-T2-1-004. T.C.S., S.Y., and M.F. acknowledge the support from the Singapore National Research Foundation NRF-NRFI-2018-04 and AcRF Tier 2 Grants MOE2019-T2-1-006 and MOE-T2EP50120-0004.

Antimony sulfoselenide (Sb

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Bismuth double perovskite Cs2AgBiBr6 strong electron–acoustic phonon interactions derail its photovoltaic aspirations., Bismuth-based double perovskite Cs2AgBiBr6 is regarded as a potential candidate for low-toxicity, high-stability perovskite solar cells. However, its performance is far from satisfactory. Albeit being an indirect bandgap semiconductor, we observe bright emission with large bimolecular recombination coefficient (reaching 4.5 ± 0.1 × 10−11 cm3 s−1) and low charge carrier mobility (around 0.05 cm2 s−1 V−1). Besides intermediate Fröhlich couplings present in both Pb-based perovskites and Cs2AgBiBr6, we uncover evidence of strong deformation potential by acoustic phonons in the latter through transient reflection, time-resolved terahertz measurements, and density functional theory calculations. The Fröhlich and deformation potentials synergistically lead to ultrafast self-trapping of free carriers forming polarons highly localized on a few units of the lattice within a few picoseconds, which also breaks down the electronic band picture, leading to efficient radiative recombination. The strong self-trapping in Cs2AgBiBr6 could impose intrinsic limitations for its application in photovoltaics.

In this work, the solvation of a nitrosyl ruthenium complex, [(CH3)4N][RuCl3(qn)(NO)] (with qn = deprotonated 8-hydroxyquinoline), which is a potential NO-releasing molecule in the bio-environment,...

Vibrational energy transfer in transition metal complexes with flexible structures in condensed phases is of central importance to catalytical chemistry processes. In this work, two molecules with different metal atoms, M(CO)5Br (where M = Mn, Re), were used as model systems, and their axial and radial carbonyl stretching modes as infrared probes. The central-metal effect on intramolecular vibrational energy redistribution (IVR) in M(CO)5Br was investigated in polar and nonpolar solvents. The linear infrared (IR) peak splitting between carbonyl vibrations increases as the metal atom changes from Mn to Re. The waiting-time dependent two-dimensional infrared diagonal- and off-diagonal peak amplitudes reveal a faster IVR process in Re(CO)5Br than in Mn(CO)5Br. With the aid of density functional theory (DFT) calculations, the central-metal effect on IVR time linearly correlates with the vibrational coupling strength between the two involved modes. In addition, the polar solvent is found to accelerate the IVR process by affecting the anharmonic vibrational potentials of a solute vibration mode.

Microemulsions are transparent, thermodynamically stable liquid mixtures of oil, water and surfactant. They typically exist in the form of micellar and bicontinuous structures, which appear to be equilibrium systems but are actually complex in structure and are difficult to characterize at the molecular level. In this work, potassium ferrocyanide [K4Fe(CN)6] and tungsten hexacarbonyl [W(CO)6] were chosen as two probe molecules for water and organic phases respectively to simultaneously explore the structures and dynamics of commonly prepared reverse micellar and bicontinuous microemulsion structures using aerosol OT (AOT) as the surfactant and isooctane as the oil phase. Even though these two structures have quite different solvent environments due to the varying geometry and boundary conditions, the steady-state infrared spectra of the C[triple bond, length as m-dash]N- stretching mode in the water phase are quite similar, and so are those of the C[triple bond, length as m-dash]O stretching mode in the oil phase. However, vibrational and anisotropic relaxation dynamics obtained from infrared pump-probe spectroscopy and spectral diffusion dynamics extracted from two-dimensional infrared spectroscopy of the two infrared chromophores in the two probe molecules are found to be quite sensitive to whether the probe molecules are in pure solvent or in a restricted microemulsion environment. The results in the water phase and oil phase are discussed separately. Our work demonstrated that ultrafast nonlinear infrared spectroscopy can be used to differentiate the structural details at the molecular level for different microemulsion systems.

Antimony sulfoselenide (Sb2 (S,Se)3 ) is a promising photoabsorber for stable and high efficiency thin film photovoltaics (PV). The unique quasi-1D (Q1D) crystal structure gives Sb2 (S,Se)3 intriguing anisotropic optoelectronic properties, which intrinsically require the optimization of crystal growth orientation, especially for electronic devices with vertical charge transport such as solar cells. Although the efficiency of Sb2 (S,Se)3 solar cells has been improved greatly through optimizing the material quality, the fundamental issue of crystal orientation control in polycrystalline films remains unsolved, resulting in charge carrier recombination losses in the device. Herein, the epitaxial growth of vertically-oriented Sb2 (S,Se)3 film on hexagonal CdS is successfully realized via a solution-based synergistic crystal growth process. The crystallographic orientation relationship between Sb2 (S,Se)3 light absorber and the CdS substrate has been rigorously investigated. The best performing Sb2 (S,Se)3 solar cell shows a high power conversion efficiency of 9.2% owing to the faster charge transport in the bulk and the efficient charge extraction across the heterojunction. This study points to a new direction to control the crystal growth of mixed-anion Sb2 (S,Se)3 , which is crucial to achieve high efficiency solar cells based on antimony chalcogenides with low dimensionality.

Binary compound antimony sulfide (Sb2S3) with its nontoxic and earth-abundant constituents, is a promising light-harvesting material for stable and high efficiency thin film photovoltaics. The intrinsic quasi-1D (Q1D) crystal structure of Sb2S3 is known to transfer photogenerated carriers rapidly along the [hk1] orientation. However, producing Sb2S3 devices with precise control of [hk1] orientation is challenging and unfavorable crystal orientations of Sb2S3 result in severe interface and bulk recombination losses. Herein, in situ vertical growth of Sb2S3 on top of ultrathin TiO2/CdS as the electron transport layer (ETL) by a solution method is demonstrated. The planar heterojunction solar cell using [hk1]-oriented Sb2S3 achieves a power conversion efficiency of 6.4%, performing at almost 20% higher than devices based on a [hk0]-oriented absorber. This work opens up new prospects for pursuing high-performance Sb2S3 thin film solar cells by tailoring the crystal orientation. Ministry of Education (MOE) Nanyang Technological University National Research Foundation (NRF) L.H.W. and S.H. acknowledge the funding support from the CREATE Programme under the Campus for Research Excellence and Technological Enterprise (CREATE), which was supported by the National Research Foundation, Prime Minister’s Office, Singapore; and the Ministry of Education (MOE) Tier 2 Project (MOE2016-T2-1-030). T.C.S and M.F. acknowledge the financial support from Nanyang Technological University start-up grant M4080514.

Vibrational energy transfer in transition metal complexes with flexible structures in condensed phases is of central importance to catalytical chemistry processes. In this work, two molecules with different metal atoms, M(CO)