Organohalide lead-perovskites have revolutionized the hybrid/organic photovoltaics landscape. Despite the fast efficiency increase, some of the materials properties related to their extraordinary photovoltaic performance remain largely not understood. Further advances in the perovskite solar cells (PSCs) field may be boosted by computational design and screening of new materials, with researchers examining material characteristics that can improve device performance and/or stability. Suitable modeling strategies may allow researchers to observe the otherwise inaccessible but crucial hetero-interfaces that control the operation of PSCs, allowing researchers the opportunity to develop new and more efficient materials and optimize processes. 

We illustrate here the performance of an integrated simulation toolbox, rooted into Density Functional Theory and many body GW methods including spin-orbit coupling, that can provide atomistic electronic structure information on the materials properties and on the crucial perovskite absorbers/metal-oxide/hole transporter material heterointerfaces.  We critically assess the accuracy of various computational approaches against the related experimental data and analyze the representative interfaces that control the device operational mechanism. In particular, we describe the structural and electronic features of the methylammonium lead iodide perovskite with various metal oxide substrates, i.e. TiO₂, Al₂O₃ and ZnO, with emphasis on the influence of the substrate in determining the perovskite growth, the preference for specific surfaces and the underlying electronic interfacial properties. Defect migration and the influence of water in MAPbI₃ degradation mechanism are also discussed. 

Figure 1. Model of the MAPbI₃ / TiO₂ interface with location of defects, and their effect on the interface electronic structure. Notice the band-bending introduced by vacancies at opposite interface sides, favoring solar cell operation.

References:

• F. De Angelis Acc. Chem. Res. 2014, 47, 3349.
• F. De Angelis et al. Chem. Rev. 2014, 114, 9708.
• A. Amat et al. Nano Lett. 2014, 14, 3608.
• P. Umari et al. Sci. Rep. 2014, 4, 4467.
• V. Roiati et al. Nano Lett. 2014, 14, 2168.
• J. M. Azpiroz et al. Energy Env. Sci. 2015, 8, 2118.
• C. Quarti et al. Energy Env. Sci. 2016, 9, 155.
• M. Saliba et al. Nature Energy 2016, 15017

Email: filippo @ thch.unipg.it, website: http://www.clhyo.org