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As an inorganic halide perovskite (IHP), CsPbI2Br has generated enormous publicity due to its suitable optical bandgap (≈1.92 eV) and thermal stability. Unfortunately, the terrible phase stability of CsPbI2Br film will cause a phase change in a wet environment and decelerate light response, seriously hindering the progression of IHP photovoltaics. Herein, a synergistic postmodification strategy with CsBr and MABr to achieve high‐quality CsPbI2Br film at a low‐temperature (≈150 °C) and positive perovskite/carbon interface is presented. Adding a small amount of MABr can promote the crystallization of perovskite. The evaporated CsBr accumulates on the grain boundaries and surface of CsPbI2Br and forms Br‐rich perovskite, which provides the protection of CsPbI2Br and segregation of water vapor. The carbon‐based perovskite solar cell (C‐PeSC) with the modified CsPbI2Br harvests a high power conversion efficiency (PCE) of 11.04%. Notably, the unpackaged cell maintains 81% of its original PCE after being stored for 21 days in an air atmosphere with 25–35% humidity. Flexible devices are further manufactured, whose PCE drops to 90% of the initial value during 150 bending cycles. The flexible device also exhibits excellent blue photodetection performances. The maximum responsivity and detection reach 0.68 A W−1 and 8.91 × 1012 Jones, respectively. These findings provide broader avenues for flexible IHP in multifunctional devices. [ABSTRACT FROM AUTHOR]

Hole‐transporting layer (HTL) materials with sufficient hole collection ability, noncorrosive nature, and easy preparation are strongly desired for the field of organic solar cells (OSCs). The development of new materials and synthetic methods has been proved to be the essential approach to improve the HTL performances. Herein, a series of thiophene oligomers TO‐P1, TO‐P2, and TO‐P3 are designed and synthesized through coupling reaction by using the polyoxometalates as the oxidizing reagents. The thiophene oligomers can be readily synthesized under ambient condition with high yield. Among the as‐prepared thiophene oligomers, TO‐P2 exhibits neutral pH, sufficient work function, and high conductivity, endowing the HTL with excellent hole collection ability. Also, TO‐P2 possesses good chemical stability and satisfied solution processability, which is important for practical use. By using TO‐P2 as HTL, OSC shows a photovoltaic efficiency of 17.25%. Furthermore, TO‐P2 is a universal HTL that can be used to fabricate efficient OSCs with various active layers. More importantly, TO‐P2 shows good compatibility with large‐area processing technique. A 1 cm2 OSC is fabricated by using a blade‐coated TO‐P2 HTL, exhibiting a power conversion efficiency of 15.0%. The easy preparation and noncorrosive nature endow TO‐P2 with great potential application in OSCs. [ABSTRACT FROM AUTHOR]

We employ few-cycle pulses to strong-field-ionize di-iodomethane (CH2I2) and femtosecond extreme ultraviolet (XUV) transient absorption spectroscopy to investigate the subsequent ultrafast dissociative ionization and vibrational wave packet dynamics. Probing in the spectral region of the I 4d core-level transitions, the time-resolved XUV differential absorption spectra reveal the population of several electronic states of CH2I2+ by strong-field ionization. Global analysis reveals three distinct time scales for the observed dynamics: 20 ± 2 fs, 49 ± 6 fs, and 157 ± 9 fs, ascribed to relaxation of the CH2I2+ parent ion from the Franck-Condon region, dissociation of high-lying excited states of CH2I2+ to I+ (3P2), CH2I, and I2+ (2Π3/2,g), and dissociation of CH2I2+ to I (2P3/2) and CH2I+, respectively. Oscillatory features in the time-resolved XUV differential absorption spectra point to the generation of vibrational wave packets in both the residual CH2I2 and the CH2I2+ parent ion. Analysis of the oscillation frequencies and phases reveals, in the case of neutral CH2I2, C–I symmetric stretching induced by bond softening and I–C–I bending driven by a combination of bond softening and R-selective depletion. In the case of CH2I2+, both the fundamental and first overtone frequencies of the I–C–I bending mode are observed, indicating large-amplitude I–C–I bending motion, in good agreement with results obtained from ab initio simulations of the XUV transition energy along the I–C–I bend coordinate. These results show that femtosecond XUV absorption spectroscopy is well-suited for studying ultrafast photodissociation and vibrational wave packet dynamics. [ABSTRACT FROM AUTHOR]

Ultrafast processes of p-bromofluorobenzene are studied with femtosecond time-resolved photoelectron imaging spectroscopy. The photoelectron image revealed four photoelectron rings centered at 0.39, 0.86, 1.13, and 1.61 eV, respectively. The inner rings are more anisotropic than the outer rings. The decay traces of the different rings were recorded separately. Sharp photoelectron energy distributions and different anisotropy parameters extracted from the images indicated resonances with Rydberg states at the (1+1′) photon energy. The quantum defect values of the four Rydberg states were determined to be 0.75, 0.52, 0.36, and ∼0, respectively, with principal quantum number of 3. The electron dephasing mechanism of the S1(B2) state corresponds to the intersystem crossing from the S1(B2) to T1(B2) state and the predissociation of the S1(B2) state via the T1(B1) state. The lifetimes of S1(B2) and T1(B2) are determined from the decay of the photoelectron signals to be 40 and 33 ps, respectively. The variety of time-dependent anisotropy parameters in the first 5 ps shows the rotational wave coherences of p-bromofluorobenzene at the S1(B2) state. [ABSTRACT FROM AUTHOR]

The photodissociation dynamics of allyl bromide was investigated at 234, 265, and 267 nm. A two-dimensional photofragment ion velocity imaging technique coupled with a [2+1] resonance-enhanced multiphoton ionization scheme was utilized to obtain the angular and translational energy distributions of the nascent Br* (2P1/2) and Br (2P3/2) atoms. The Br fragments show a bimodal translational energy distribution, while the Br* fragments reveal one translational energy distribution. The vertical excited energies and the mixed electronic character of excited states were calculated at ab initio configuration interaction method. It is presumed that the high kinetic energy bromine atoms are attributed to the predissociation from 1(ππ*) or 1(πσ*) state to the repulsive 1(nσ*) state, and to the direct dissociation from 3(nσ*) and 3(πσ*) states, while the low kinetic energy bromine atoms stem from internal conversion from the lowest 3(ππ*) state to 3(πσ*) state. [ABSTRACT FROM AUTHOR]

Abstract: The photodissociation of n-C5H11Br at 234nm has been investigated utilizing the ion velocity imaging technique. The two-dimensional images provide detailed information on the translational energy distributions and anisotropy parameters. The obtained translational energy distributions corresponding to the Br and Br∗ fragments have been fitted by a single Gaussian function, respectively. The anisotropies for the Br and Br∗ channels are measured to be β =1.08 and 1.84, respectively. The contributions of each electronic state have been estimated and the probability of nonadiabatic transition between 3Q0 and 1Q1 states is determined to be 0.47. [Copyright &y& Elsevier]

Abstract: The photodissociation dynamics of CH2Br2 was investigated near 234 and 267nm. A two-dimensional photofragment ion velocity imaging technique coupled with a [2+1] resonance-enhanced multiphoton (REMPI) ionization scheme was utilized to obtain the angular and translational energy distributions of the nascent Br (2 P 3/2) and Br* (2 P 1/2) atoms. The obtained translational energy distributions of Br and Br* are found consist of two components which should be come from the radical channel and secondary dissociation process, respectively. It is suggested that the symmetry reduction from to C s during photodissociation invokes a non-adiabatic coupling between the 2B1 and A1 states. Consequently, the higher internal energy distribution of Br channel than Br* formation channel and the broader translational energy distribution of the former are presumed correlate with a variety of vibrational excitation disposal at the crossing point resulting from the larger non-adiabatic crossing from 2B1 to A1 state than the reverse crossing. Moreover, the measured anisotropy parameter β indicate that fragments recoil along the Br–Br direction mostly in the photodissociation. [Copyright &y& Elsevier]

Studies of ultrafast molecular dynamics induced by intense laser fields can reveal new approaches to manipulating chemical reactions in the strong-field regime. Here, we show that intense few-cycle laser pulses can induce the spin-orbit state-selective C-I dissociation of the iodomethane cation (CH 3 I + ) in the X̃ electronic state. Irradiation of CH 3 I by 6 fs laser pulses with peak intensities of 1.9 × 10 14 W/cm 2 followed by femtosecond extreme ultraviolet probing of the iodine 4d core-level transitions reveals dissociation of the CH 3 I + X̃ 2 E 1/2 state with a time constant of 0.76 ± 0.16 ps. By contrast, the X̃ 2 E 3/2 spin-orbit ground state does not exhibit any appreciable dissociation on the picosecond time scale. The observed spin-orbit state-selective dissociation of the X̃ state is rationalized in terms of the laser-induced coupling to the à state. Our results suggest that the intense-laser control of photodissociation channels can be potentially extended to spin-orbit split states.