In Situ Self‐Elimination of Defects via Controlled Perovskite Crystallization Dynamics for High‐Performance Solar Cells

Abstract

Understanding and controlling the crystallization process is critical to achieving high‐quality perovskite films and efficient solar cells. Herein, we identified that one key issue in the formation of formamidinium lead iodide (FAPbI3) defects is the participation of the intermediates in the crystallization process. A comprehensive picture of structural and carrier evolution during crystallization was demonstrated using a combination of in situ grazing‐incidence wide‐angle X‐ray scattering, UV‐Vis, and photoluminescence spectroscopies. Three crystallization stages were registered for the commonly observed conversion pathway of precursors – δ‐FAPbI3 intermediate – α‐FAPbI3, during which the spontaneous generation of defects was found. We found that a hydrogen sulfate‐based ionic liquid additive enabled the phase conversion pathway of precursors – solvated intermediates – α‐FAPbI3, during which the spontaneous generation of δ‐FAPbI3 can be effectively circumvented. Both growth kinetics at the initial crystallization stage and the following recrystallization of α‐FAPbI3 were significantly prolonged because of the additional exchange process between solvents and FA+, which resulted in the self‐elimination of defects during crystallization. Therefore, the improved crystallization dynamics led to larger grain sizes and fewer defects within thin films. The improved perovskite crystallization dynamics finally transformed into high‐performance solar cells under one‐sun illumination (AM 1.5 G) with efficiency as high as 25.14% at 300 K. These cells delivered a PCE of 26.12% at 240 K, which might open up a new era of application of this emerging photovoltaic technology to low‐temperature environments such as near‐space and polar regions.This article is protected by copyright. All rights reserved

Halide Segregated Crystallization of Mixed-Halide Perovskites Revealed by In Situ GIWAXS

“…The increasing orientational order of methylammonium-based perovskite materials upon bromide incorporation is likely a general motif, which has been reported in literature before . The azimuthal intensity plots in Figure S3 visualize the orientational order of the different mixtures for both fabrication methods, similar to established literature. , …”

“…23 The azimuthal intensity plots in Figure S3 visualize the orientational order of the different mixtures for both fabrication methods, similar to established literature. 24,25 The degree of orientation does not change upon halide segregation such that both split peaks have the same orientation as the pristine samples (Figure 2c,d). This behavior is consistent with halide segregation occurring via ion migration in the existing perovskite crystallites instead of recrystallization or via amorphous phases.…”

Custom-tailored solvent engineering for efficient wide-bandgap perovskite solar cells with a wide processing window and low VOC losses

“…The density of trap state ( N trap ) can be calculated using the following equation: N trap = (2 εε 0 V TFL )/( qL 2 ). 33,34 Apparently, the target perovskite film has a reduced N trap of 7.17 × 10 14 cm −3 (Fig. 2k) than 1.96 × 10 15 cm −3 (Fig.…”

Spiro[fluorene-9,9′-xanthene]-Based Hole-Transporting Materials for Photovoltaics: Molecular Design, Structure–Property Relationship, and Applications

“…It has contributed to record-breaking PCEs of 8.0% for sDSCs and 26% for PSCs when employing spiro-OMeTAD as the HTM. 41,42 Despite continuous efforts to explore new organic HTMs, spiro-OMeTAD remains a premier choice for both sDSCs and PSCs owing to its outstanding combination of properties. However, the wide-scale industrial application of spiro-OMeTAD has certain challenges.…”

“…Spiro-OMeTAD was originally introduced in 1998 for sDSCs and has since then witnessed significant research and development, leading to remarkable progress in the photovoltaic domain. It has contributed to record-breaking PCEs of 8.0% for sDSCs and 26% for PSCs when employing spiro-OMeTAD as the HTM. , Despite continuous efforts to explore new organic HTMs, spiro-OMeTAD remains a premier choice for both sDSCs and PSCs owing to its outstanding combination of properties. However, the wide-scale industrial application of spiro-OMeTAD has certain challenges.…”