Metal Halide Perovskite Surfaces with Mixed A‐Site Cations: Atomic Structure and Device Stability

Abstract

Mixing cations in the perovskite structure has been shown to improve optoelectronic device performance and stability. In particular, CsxMA1‐xPbBr3 (MA = CH3NH3) has been used to build high‐efficiency light‐emitting diodes. Despite those advantages, little is known about the exact location of the cations in the mixed perovskite film, and how cation distribution affects device properties and stability. By using scanning tunneling microscopy , the exact atomic structure of the mixed cation CsxMA1‐xPbBr3 perovskite interface is revealed. In addition, X‐ray photoelectron spectroscopy, ultraviolet photoemission spectroscopy and inverse photoemission spectroscopy are used to study the stability and electronic properties of the CsxMA1‐xPbBr3 perovskite film. Partial substitution of MA+ by Cs+ induces a modification of the perovskite surface structure, leading to improved device stability is shown. These results provide a better understanding of the key parameters involved in the stability of mixed cation perovskite solar cells.

Tale of Two Sites: Band-Gap Tuning in AgBiI4 through Site-Selective Alloying

“…During the B-site alloying, the introduction of antimony at the bismuth site led to a large shift in the V CPD in the opposite direction, from −0.11 to +0.26 V. Such a change in the V CPD , when calibrated, resulted in a shift of 0.37 eV in the work function; the end-member here (AgSbI 4 ) yielded a work function of 4.50 eV. The large change in the work function during the B-site alloying, as compared to that under an A-site alloying process, is in agreement with the reported results . This is because the electronic properties of halide perovskites mostly rely on the B–X bonds, whereas the A-site cation mostly plays a role in the charge carrier dynamics and is a spectator cation in the band formation process.…”

“…While the A-site alloying decreased the V CPD , the alloying at the B-site increased the parameter. For a quantitative analysis, the distribution of the V CPD , as obtained from the KPFM topographies in films of different alloys, is presented in 43 This is because the electronic properties of halide perovskites mostly rely on the B−X bonds, whereas the A-site cation mostly plays a role in the charge carrier dynamics and is a spectator cation in the band formation process. The A-site cation can, however, induce a distortion in the octahedral stacking and thereby influence the B−X bond lengths as well and hence the orbital overlaps, which in turn would have some secondary effects on the electronic structures of the perovskite compounds.…”

Pathways of Water-Induced Lead-Halide Perovskite Surface Degradation: Insights from In Situ Atomic-Scale Analysis

“…Both methods provide effectively identical surface conditions . Since 2015, the atomic structures of pristine perovskite surfaces and defect structure and dynamics have been extensively investigated using scanning tunneling microscopy (STM) in conjunction with density functional theory (DFT) calculations, which have provided a fundamental understanding of the correlation between the surface structures and the optoelectronic properties of OHPs. − However, the STM measurements reported up to the present were obtained under UHV conditions and at low temperature, i.e., liquid nitrogen or helium temperature, or at ultralow water vapor exposure . In our previous reports, utilizing contact-mode atomic force microscopy (AFM) measurements together with DFT calculations, we showed that UHV-cleaved pristine MAPbBr 3 surfaces exhibit two surface domains, namely MA–Br and Pb–Br terminated surfaces (see Figure S1), and the degradation pathways in UHV conditions. , We reported that, in UHV chambers, the residual water of the partial pressure of 8 × 10 –10 Torr induced a slow degradation of MAPbBr 3 surfaces, over a time scale of weeks, leading to the formation of PbBr 2 clusters.…”

The Effect of the Alkyl Chains of the Alkylammonium Pesudohalide Additives on the Performance of Dion Jacobson Perovskite Solar Cells

“…In order to improve the quality of the DJ perovskite films, researchers have made attempts in manipulating the structures of the spacer cations, the composition of the small A cations, and the deposition methods and the additives. [24][25][26][27][28] In 2017, Kanatzidis et al reported a PCE ≈7% for the first examples of the DJHPSCs using 3-(Aminomethyl)piperidinium (3AMP) as the spacer cation. [11] One year later, authors from the same group improved the crystallinity of the perovskite film by using a mixture of FA and MA cations to construct the DJP film, obtaining a PCE of 12.04%.…”