Abstract
Two-dimensional halide perovskites (2D PVSKs) have drawn tremendous attentions owing to their outstanding ambient stability. However, the random orientation of layered crystals severely impedes the out-of-plane carrier transport and limits the solar cell performance. An in-depth understanding coupled with an effective control of the crystallization in 2D PVSKs is the crux for highly efficient and durable devices. In this contribution, we accidentally discovered that the crystallization of 2D PVSKs can be effectively regulated by so-called ′intermittent spin-coating (ISC)′ process. Combined analyses of in(ex)-situ grazing-incidence wide-angle X-ray scattering with time-of-flight secondary ion mass spectrometry distinguish the interface initialized bottom-up crystallization upon ISC treatment from the bi-directional one in the conventional spin-coating process, which results in significantly enhanced crystal orientation and thus facilitated carrier transport as confirmed by both electrical measurements and ultrafast spectroscopies. As a result, the p-i-n architecture planar solar cells based on ISC fabricated paradigm PEA2MA3Pb4I13 deliver a respectable efficiency of 11.2% without any treatment, which is three-fold improvement over their spin-coated counterparts and can be further boosted up to 14.0% by NH4Cl addition, demonstrating the compatibility of ISC method with other film optimization strategies.
Highlights
Two-dimensional halide perovskites (2D PVSKs) have drawn tremendous attentions owing to their outstanding ambient stability
Compared to the conventional SC process, the intermittent spincoating (ISC) method enables a delicate modulation of the supersaturation both on liquid-gas surface and at liquid-substrate interface, which determines the initial nucleation site and the subsequent crystal growth direction
Taking a paradigm PEA2MA3Pb4I13 system as an example, we discover that the samples treated by a short ISC time exhibit significantly red-shifted optical features, improved vertical orientation, elevated carrier mobility, and facilitated inter-phase charge transfer, all of which are collectively conducive to enhanced device performance in comparison to reference SC samples
Summary
Two-dimensional halide perovskites (2D PVSKs) have drawn tremendous attentions owing to their outstanding ambient stability. Based on the above results, the short ISC sample exhibits better crystallinity and possibly transfers charge carriers more efficiently from low-n to high-n phases than long ISC ones.
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