Filippo De Angelis

Anion/cation vacancies located at different interfaces in perovskite solar cells may modify the electronic energy landscape, hampering charge extraction, and presumably contributing to the observed <italic>J–V</italic> hysteresis.

We report the low-frequency resonant Raman spectrum of methylammonium lead-iodide, a prototypical perovskite for solar cells applications, on mesoporous Al2O3. The measured spectrum assignment is assisted by DFT simulations of the Raman spectra of suitable periodic and model systems. The bands at 62 and 94 cm(-1) are assigned respectively to the bending and to the stretching of the Pb-I bonds, and are thus diagnostic modes of the inorganic cage. We also assign the librations of the organic catio

Electron/hole traps related to interstitial iodine defects show the typical features of iodine photo-electrochemistry, inducing MAPbI₃ defect tolerance.

We report optical measurements on MAPbI₃solar cells, together with<italic>ab initio</italic>simulations, to investigate the material property changes across the tetragonal to cubic phase transition.

ADVERTISEMENT RETURN TO ISSUEPREVReviewNEXTTheoretical Studies on Anatase and Less Common TiO2 Phases: Bulk, Surfaces, and NanomaterialsFilippo De Angelis†, Cristiana Di Valentin‡, Simona Fantacci†, Andrea Vittadini§, and Annabella Selloni*∥View Author Information† Computational Laboratory for Hybrid Organic Photovoltaics (CLHYO), Istituto CNR di Scienze e Tecnologie Molecolari, Via Elce di Sotto 8, I-06123 Perugia, Italy‡ Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, I-20

The photoinduced removal of trap states due to Frenkel defects is found to enhance the PLQE of perovskite thin films.

We report a combined experimental and theoretical study on the origin of the different open circuit potentials observed in dye-sensitized solar cells using Ru(II)-polypyridyl homoleptic and heteroleptic sensitizers. We have measured the photovoltaic data of different sensitizers and used DFT calculations to analyze the electronic structure of dye-sensitized TiO(2) nanoparticles. Heteroleptic sensitizers adsorb onto TiO(2) via a single bipyridine, leading to a TiO(2) conduction band downshift and

We propose a new model of defect formation and ion migration at the surfaces/grain boundaries of lead-halide perovskites, based on ab initio calculations. Inspired by the spread of experimentally measured activation energies for ion migration in similar lead-iodide perovskites, we define an effective defect formation energy weighed upon surface and bulk contributions. We thus link the large variation in measured activation energies for ion migration to the different defect formation energies of

The presence of various types of chemical interactions in metal-halide perovskite semiconductors gives them a characteristic "soft" fluctuating structure, prone to a wide set of defects. Understanding of the nature of defects and their photochemistry is summarized, which leverages the cooperative action of density functional theory investigations and accurate experimental design. This knowledge is used to describe how defect activity determines the macroscopic properties of the material and rela

We present a theoretical study of the lineup of the LUMO of Ru(II)-polypyridyl (N3 and N719) molecular dyes with the conduction band edge of a TiO(2) anatase nanoparticle. We use density functional theory (DFT) and the Car-Parrinello scheme for efficient optimization of the dye-nanoparticle systems, followed by hybrid B3LYP functional calculations of the electronic structure and time-dependent DFT (TDDFT) determination of the lowest vertical excitation energies. The electronic structure and TDDF

We report a thorough theoretical and computational investigation of the effect of dye adsorption on the TiO2 conduction band energy in dye-sensitized solar cells that is aimed at assessing the origin of the shifts induced by surface adsorbed species in the position of the TiO2 conduction band. We thus investigate a series of working dye sensitizers and prototypical surface adsorbers and apply an innovative approach to disentangle electrostatic and charge-transfer effects occurring at the crucial

Tin halide perovskites represent the only realistic route toward lead-free perovskite optoelectronics. Despite significant progress, however, the device efficiency and stability of solar cells are still limited by the perovskite self-p-doping and by Sn(II) oxidation to Sn(IV). By employing state-of-the-art density functional theory simulations, we unveil the mechanistic features and energetics of Sn(II) → Sn(IV) oxidation in pristine and defective models. Surprisingly, tin oxidation is predicted

We present a combined density functional theory (DFT)/time-dependent density functional theory (TDDFT) study of the geometry, electronic structure, and absorption and emission properties of the tetranuclear "cubane" Cu4I4py4 (py = pyridine) system. The geometry of the singlet ground state and of the two lowest triplet states of the title complex were optimized, followed by TDDFT excited-state calculations. This procedure allowed us to characterize the nature of the excited states involved in the

We report a combined experimental and theoretical study on cationic Ir(III) complexes for OLED applications and describe a strategy to tune the phosphorescence wavelength and to enhance the emission quantum yields for this class of compounds. This is achieved by modulating the electronic structure and the excited states of the complexes by selective ligand functionalization. In particular, we report the synthesis, electrochemical characterization, and photophysical properties of a new cationic I