Halide perovskites recently emerged as multifaceted light-harvesting, light-emitting and charge-transporting materials for efficient photovoltaic, light-emitting and optoelectronic devices. The major theme of this symposium is the fundamental understanding of their optoelectronic properties on different time, length and energy scales that underpin the extraordinary behavior of these materials. The findings are key requirements for a better understanding of the myriad of challenges observed in halide perovskite research that are urgently needed to advance the field towards highly efficient, stable, low toxic, and large-area scalable devices. These challenges span the areas of interfaces, defects, instabilities, and photophysics - on both experimental and theoretical levels. Material categories include lead-based; lead-free; low-dimensional, polycrystalline, mixed-dimensional, single crystal, and nanostructured halide perovskites. One focus will be on the interplay between the structural features of halide perovskites and the physical processes determining their optoelectronic performance. The role of the crystal lattice will be discussed based on TEM, XRD … results including defect analysis and first principle calculations. This discussion includes modelling of the nature of the charge carriers (excited carrier-phonon interaction, exciton dynamic, polaron formation etc). Advances in understanding these mechanisms is the key to exploit the full potential of perovskites, and design the most efficient light emitting diodes, solar cells and lasers. Hot-carriers, multiband, or multiple exciton generation phenomena will be subject in context of structure interaction through processes such as carrier scattering and thermalization as groundwork for the viability of next generation photovoltaics and optoelectronic devices in general. From the electrical characterization perspective, the band alignment and charge distribution of the devices at different working regimes will be discussed, comprising methods such as capacitance and impedance spectroscopy. These are useful tools to monitor physical processes defined by different characteristic frequencies, enabling independent characterization on different time scales: fast electronic events ~ns (such as recombination and trapping kinetics), as well as slow ionic effects ~ms. Another focus will be on the understanding and control of defects in halide perovskites and their influence on optoelectronic properties. The energetic positions of electronic bands and their alignment with selective contacts will be discussed including the relevance of interfacial effects such as interface dipole formation on charge carrier transport. Interfaces cover intralayer grain boundaries within the photoabsorber. Contributions should address the correlations between synthesis and defect formation as well as interface engineering, surface/interface passivation and device performance. Discussions on novel 2D/3D interfaces are also welcomed. Key requirements for achieving maximum device efficiencies are the control of defects, interface passivation, and tailoring of the electronic energy levels of the adjacent transport layers to guarantee efficient charge transport.

This symposium will allow stimulating discussion about these effects, which will aid the advancement of hybrid perovskite devices through a clearer understanding of the fundamental processes governing these fascinating materials.

absorption diffusion electrical properties electronic structure electron-phonon interactions ferroelectricity organometallic Pb photoconductivity