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Metal Halide Perovskite Polycrystalline Films Exhibiting Properties of Single Crystals

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Brenes, R 
Guo, D 
Osherov, A 
Noel, NK 
Eames, C 


Metal halide perovskites are generating enormous excitement for use in solar cells and light-emission applications, but devices still show substantial non-radiative losses. Here, we show that by combining light and atmospheric treatments, we can increase the internal luminescence quantum efficiencies of polycrystalline perovskite films from 1% to 89%, with carrier lifetimes of 32 μs and diffusion lengths of 77 μm, comparable with perovskite single crystals. Remarkably, the surface recombination velocity of holes in the treated films is 0.4 cm/s, approaching the values for fully passivated crystalline silicon, which has the lowest values for any semiconductor to date. The enhancements translate to solar cell power-conversion efficiencies of 19.2%, with a near-instant rise to stabilized power output, consistent with suppression of ion migration. We propose a mechanism in which light creates superoxide species from oxygen that remove shallow surface states. The work reveals an industrially scalable post-treatment capable of producing state-of-the-art semiconducting films.



perovskite solar cells, photoluminescence, passivation, semiconductors, photovoltaics, time-resolved microwave conductivity, light-emission

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Cell Press
European Commission (622630)
Engineering and Physical Sciences Research Council (EP/M005143/1)
Engineering and Physical Sciences Research Council (EP/P02484X/1)
S.D.S. has received funding from the European Union's Seventh Framework Program (Marie Curie Actions) under REA grant number PIOF-GA-2013-622630. This work made use of the Shared Experimental Facilities supported in part by the MRSEC Program of the National Science Foundation (NSF) under award number MDR – 1419807. R.B. acknowledges support from the MIT Undergraduate Research Opportunities Program (UROP). A.O. acknowledges support from the NSF under grant no. 1605406 (EP/L000202). D.G. acknowledges the China Scholarship Council for funding, file no. 201504910812. The authors acknowledge funding from the Engineering and Physical Sciences Research Council (EPSRC) under EP/P02484X/1 and the Programme Grant EP/M005143/1. M.S.I. and C.E. acknowledge support from the EPSRC Program grant on Energy Materials (EP/KO16288) and the Archer HPC/MCC Consortium (EP/L000202). E.M.H. gratefully acknowledges the Netherlands Organization for Scientific Research (NWO) Echo number 712.014.007 for funding. The work was also partially supported by Eni S.p.A. via the Eni-MIT Solar Frontiers Center. The authors thank Mengfei Wu and Marc Baldo for access to an integrating sphere, Jay Patel and Michael Johnston for EQE verifications, and Eli Yablonovitch and Luis Pazos-Outón for helpful discussion.