film deposition process to achieve desired morphology and microstructure. [2-6] Most of the high-efficiency PSCs were produced by either one-step or two-step fabrication methods. The very first MAPbI 3-based PSC was fabricated via a one-step spincoating process developed by Kojima et al. in 2009. [7] However, the one-step fabricated perovskite film typically exhibited a dendritic morphology with poor coverage. To address the morphology issue, a two-step spin-coating process was developed by Xiao et al. [8] and Im et al. [9] in 2014, which consisted of sequential depositions of an inorganic PbI 2 layer and an organic salt MAI. This two-step method gave rise to compact and pinhole-free MAPbI 3 perovskite films, significantly increasing the efficiency of MA-based PSCs to ≈17%. [9] In 2015, the record PCE received another boost through the development of a simpler antisolvent-assisted one-step method, which could form a very uniform perovskite thin film by promoting the crystallization process. [4,10] Meanwhile, MA cations were replaced by CH(NH 2) 2 + (FA) cations to improve the light Two-step-fabricated FAPbI 3-based perovskites have attracted increasing attention because of their excellent film quality and reproducibility. However, the underlying film formation mechanism remains mysterious. Here, the crystallization kinetics of a benchmark FAPbI 3-based perovskite film with sequential A-site doping of Cs + and GA + is revealed by in situ X-ray scattering and first-principles calculations. Incorporating Cs + in the first step induces an alternative pathway from δ-CsPbI 3 to perovskite α-phase, which is energetically more favorable than the conventional pathways from PbI 2. However, pinholes are formed due to the nonuniform nucleation with sparse δ-CsPbI 3 crystals. Fortunately, incorporating GA + in the second step can not only promote the phase transition from δ-CsPbI 3 to the perovskite α-phase, but also eliminate pinholes via Ostwald ripening and enhanced grain boundary migration, thus boosting efficiencies of perovskite solar cells over 23%. This work demonstrates the unprecedented advantage of the two-step process over the one-step process, allowing a precise control of the perovskite crystallization kinetics by decoupling the crystal nucleation and growth process.
Figure 5. Performance of LED devices of Q-2D perovskite. a) Cross-section scanning electron microscopy (SEM) image of the device; scale bar: 500 nm. b,c) Current-efficiency-voltage (CE-V) curves of the Q-2D perovskite LED devices with different alkali-metal ions incorporated (b) and different amounts of KBr incorporated (c). d) J-V-L-EQE curves of the champion device with 0.5KBr added. e) Histogram of maximum EQE measured from 50 devices with 0.5KBr added. f) Stability of the perovskite LED measured at a constant current density of 0.25 mA cm -2 , with an initial luminance around 140 cd m -2 .
published version features the final layout of the paper including the volume, issue and page numbers.
Link to publication
General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal.If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User
DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers.
Link to publication
General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal.If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User Agreement:
published version features the final layout of the paper including the volume, issue and page numbers.
Link to publication
General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal.If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.