Towards an understanding of electronic transport properties of hybrid perovskite solar cells – TRANSHYPERO

TRANSHYPERO aims at inspecting theoretically dielectric properties as well as hole and electron transport properties in hybrid organic/inorganic perovskite (HOP) based solar cells.

Although HOP materials have been known for several decades, it is only very recently that their performances for photovoltaic (PV) devices have been revealed. In fact, the conversion efficiency of solar energy to electrical power of HOP-based solar cells went from 3.8% in 2009 to over 20% in 2015. Moreover, these materials offer easy processability (low temperature, full solution process) and thus open the way towards low cost production that might bring solar energy to grid parity within the next 5 years, in agreement with the most optimistic scenario from the European photovoltaic industry association (EPIA). Nevertheless this can only be achieved if two major issues are solved. First, the lifetime of HOP materials under working conditions is dramatically low as compared to the 35 years expected service life. In addition, the current most efficient HOP materials for PV cells contain lead, which might be hazardous especially in the case of leaks. To bypass these obstacles, there is an urgent need for a better understanding of the astonishing performances of these new solar cells, including their transport properties. Indeed, HOP do not only provide broad and efficient absorption across the solar spectrum (visible-light sensitizer) but also high carrier mobility (transporting layer).

Three major goals for TRANSHYPERO to reach are defined in this proposal. The first objective aims to determine the structure and electronic structure of multiple interfaces of HOP with charge selective interlayers and contacts. Selection of suitable materials will benefit from our ongoing collaboration with experimentalists from the Los Alamos National Laboratory (LANL), involved in the development of lab scale devices, and from the expertise developed at Rennes on HOP between the Institut des Sciences Chimiques de Rennes and FOTON laboratory (INSA Rennes). Then, the dielectric properties of HOP and HOP-based structures will be simulated and examined in detail. Finally, the transport properties will be computed for complete cells, benefiting from the experience of the Principal Investigator (PI) in the simulation of electronic transport. Collaborators from LANL will also provide complementary state-of-the-art theoretical skills, e.g. in non-equilibrium phenomena

This challenging proposal requires a strong implication of the recently recruited young PI, but also the expertise of C. Katan in HOP materials. In addition, to tackle this ambitious project, additional manpower is needed (postdoctoral fellow) as well as financial support to ensure fruitful collaboration with LANL. In conjunction with the existing expertise of Rennes in the simulation and physics of HOP, TRANSHYPERO arises from the recent recruitment of a young computational chemist having specific skills in the simulation of transport in semiconductors. Therefore, it matches the ambition of the JCJC program that encourages the emergence of an independent project for a young researcher in the team to which he belongs.

The expected outcomes of TRANSHYPERO will naturally benefit to the PV community and to the HOP community. The new approach developed aims to be many-sided in nature, it shall also be applicable to other types of semiconductors, and thus should have significant impact in solid-state chemistry and physics. Moreover it gives the opportunity to train future generation of computational chemists towards integrated device-oriented approaches making the most of state-of-the-art theoretical skills to address major societal challenges.