Three-dimensional organic–inorganic perovskites have emerged as one of the most promising thin-film solar cell materials owing to their remarkable photophysical properties1,2,3,4,5, which have led to power conversion efficiencies exceeding 20 per cent6,7, with the prospect of further improvements towards the Shockley–Queisser limit for a single‐junction solar cell (33.5 per cent)8. Besides efficiency, another critical factor for photovoltaics and other optoelectronic applications is environmental stability and photostability under operating conditions9,10,11,12,13,14,15. In contrast to their three-dimensional counterparts, Ruddlesden–Popper phases—layered two-dimensional perovskite films—have shown promising stability, but poor efficiency at only 4.73 per cent13,16,17. This relatively poor efficiency is attributed to the inhibition of out-of-plane charge transport by the organic cations, which act like insulating spacing layers between the conducting inorganic slabs. Here we overcome this issue in layered perovskites by producing thin films of near-single-crystalline quality, in which the crystallographic planes of the inorganic perovskite component have a strongly preferential out-of-plane alignment with respect to the contacts in planar solar cells to facilitate efficient charge transport. We report a photovoltaic efficiency of 12.52 per cent with no hysteresis, and the devices exhibit greatly improved stability in comparison to their three-dimensional counterparts when subjected to light, humidity and heat stress tests. Unencapsulated two-dimensional perovskite devices retain over 60 per cent of their efficiency for over 2,250 hours under constant, standard (AM1.5G) illumination, and exhibit greater tolerance to 65 per cent relative humidity than do three-dimensional equivalents. When the devices are encapsulated, the layered devices do not show any degradation under constant AM1.5G illumination or humidity. We anticipate that these results will lead to the growth of single-crystalline, solution-processed, layered, hybrid, perovskite thin films, which are essential for high-performance opto-electronic devices with technologically relevant long-term stability.
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This work at LANL was LANL LDRD programme (A.D.M., G.G., J.-C.B. and S.T.). Work at Northwestern University was supported as part of the ANSER Center, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, under Award No. DE-SC0001059. Use of the Advanced Photon Source at Argonne National Laboratory was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. Work at INSA de Rennes was performed using high-performance computational resources from the French national centres (GENCI/CINES/IDRIS grant 2015-c2012096724), Cellule Energie du CNRS (SOLHYBTRANS Project) and the University of Rennes 1 (Action Incitative,Défis Scientifique Emergents 2015). J.E.’s work is also supported by the Fondation d’entreprises banque Populaire de l’Ouest (Grant PEROPHOT 2015). The work at Purdue University was supported by the Bay Area PV Consortium (a Department of Energy project with Prime Award number DE-EE0004946). This work at LANL was done in part at the Center for Nonlinear Studies (CNLS) and the Center for Integrated Nanotechnologies (CINT). R.V. acknowledges the support of the NSF DMR-1352099.
Extended data figures
This file contains a Supplementary Discussion, Supplementary Tables 1-4 and Supplementary References.