Interfacial engineering has been shown to play a vital role in boosting the performance of perovskite solar cells in the past few years. Here we demonstrate that caesium bromide (CsBr), as an interfacial modifier between the electron collection layer and the CH3NH3PbI3−xClx absorber layer, can effectively enhance the stability of planar heterojunction devices under ultra violet (UV) light soaking. Additionally, the device performance is improved due to the alleviated defects at the perovskite-titania heterojunction and enhanced electron extraction

All-inorganic perovskite solar cells provide a promising solution to tackle the thermal instability problem of organic-inorganic perovskite solar cells (PSCs). Herein, we designed an all-inorganic perovskite solar cell with novel structure (FTO/NiO /CsPbIBr/ZnO@C/Ag), in which ZnO@C bilayer was utilized as the electron-transporting layers that demonstrated high carrier extraction efficiency and low leakage loss. Consequently, the as-fabricated all-inorganic CsPbIBr perovskite solar cell yielded a power conversion efficiency (PCE) as high as 13.3% with a V of 1.14 V, J of 15.2 mA·cm, and FF of 0.77. The corresponding stabilized power output (SPO) of the device was demonstrated to be ∼12% and remarkably stable within 1000 s. Importantly, the obtained all-inorganic PSCs without encapsulation exhibited only 20% PCE loss with thermal treatment at 85 °C for 360 h, which largely outperformed the organic-species-containing PSCs. The present study demonstrates potential in overcoming the intractable issue concerning the thermal instability of perovskite solar cells.

The highly developed crystallization process with respect to perovskite thin films is favorable for efficient solar cells. Here, an innovative intermolecular self-assembly approach was employed to retard the crystallization of PbI2 in dimethylformamide (DMF) by additional solvent of dimethyl sulfoxide (DMSO), which was proved to be capable of coordinating with PbI2 by coordinate covalent bond. The obtained PbI2(DMSO)x (0 ≤ x ≤ 1.86) complexes tend to be closely packed by means of intermolecular self-assembly. Afterward, an intramolecular exchange of DMSO with CH3NH3I (MAI) enabled the complexes to deform their shape and finally to reorganize to be an ultraflat and dense thin film of CH3NH3PbI3. The controllable grain morphology of perovskite thin film allows obtaining a power conversion efficiency (PCE) above 17% and a stabilized power output above 16% within 240 s by controlling DMSO species in the complex-precursor system (CPS). The present study gives a reproductive and facile strategy toward high quality of perovskite thin films and efficient solar cells.

A higher resolution magnetic bottle photoelectron spectrometer for the study of the electronic structure of size-selected metal clusters is presented. The initial study on Fe n Ϫ ͑nϭ3-24͒ is reported at a photon energy of 3.49 eV. The photoelectron spectra of these clusters exhibit sharp features throughout the size range. The spectra for Fe 3-8Ϫ show large size dependence with many resolved features. The spectra for Fe 9-15 Ϫ exhibit some similarity with each other, all with a rather sharp feature near the threshold. An abrupt spectral change occurs at Fe 16 Ϫ , then again at Fe 19 Ϫ and Fe 23 Ϫ . These photoelectron spectral changes coincide remarkably with changes of the cluster reactivity with H 2 . Extended Hückel molecular orbital ͑EHMO͒ calculations are performed for all the clusters to aid the spectral interpretations. The calculations yield surprisingly good agreement with the experiment for clusters beyond Fe 9 when body-centered cubic ͑bcc͒ structures are assumed for Fe 9-15 and a similarly close-packed structure with a bcc Fe 15 core for the larger clusters. The EHMO calculations allow a systematic interpretation of the sharp photoelectron spectral features in Fe 9-15 Ϫ and reproduced the abrupt spectral change taking place from Fe 15Ϫ to Fe 16 Ϫ . Most importantly, the reactivity changes of the clusters with H 2 are successfully explained based on the detailed electronic structures of the clusters, as revealed from the photoelectron spectroscopy ͑PES͒ spectra and the theoretical calculations. The calculations also correctly predict the existence of magnetism in these clusters and yield reasonable values for the cluster magnetic moments.