Impact of Film Stoichiometry on the Ionization Energy and Electronic Structure of CH3NH3PbI3 Perovskites

Emara, Jennifer; Schnier, Tobias; Pourdavoud, Neda; Riedl, Thomas; Meerholz, Klaus; Olthof, Selina

doi:10.1002/adma.201503406

Cited by 157 publications

(212 citation statements)

References 32 publications

Supporting

Mentioning

195

Contrasting

Order By: Relevance

“…For the thick layers we find two different E VB , in agreement with the Wf measurements, a higher one for ITO (E VB = 1.71 eV) and PEIE (E VB = 1.78 eV), and a lower one for PEDOT:PSS (E VB = 1.14 eV) and MoO 3 (E VB = 1.24 eV). From the combined Wf and E VB measurements, the ionization energies can be calculated which are for the thick layers almost identical, yielding IE = 5.9 ± 0.1 eV, in agreement with previously reported values where the linear extrapolation of the density of states is used5051.…”

Section: Resultssupporting

confidence: 88%

Substrate-dependent electronic structure and film formation of MAPbI3 perovskites

Olthof

Meerholz

2017

Sci Rep

Self Cite

253

326

View full text Add to dashboard Cite

We present investigations on the interface formation between the hybrid perovskite MAPbI3 and various substrates, covering a wide range of work functions. The perovskite films are incrementally evaporated in situ while the electronic structure is evaluated using photoelectron spectroscopy. Our results show that there is an induction period in the growth of the perovskite during which volatile compounds are formed, catalyzed by the substrate. The duration of the induction period depends strongly on the nature of the substrate material, and it can take up to 20–30 nm of formal precursor deposition before the surface is passivated and the perovskite film starts forming. The stoichiometry of the 2–3 nm thin passivation layer deviates from the expected perovskite stoichiometry, being rich in decomposition products of the organic cation. During the regular growth of the perovskite, our measurements show a deviation from the commonly assumed flat band condition, i.e., dipole formation and band bending dominate the interface. Overall, the nature of the substrate not only changes the energetic alignment of the perovskite, it can introduce gap states and influence the film formation and morphology. The possible impact on device performance is discussed.

show abstract

Section: Resultssupporting

confidence: 88%

Substrate-dependent electronic structure and film formation of MAPbI3 perovskites

Olthof

Meerholz

2017

Sci Rep

Self Cite

253

326

View full text Add to dashboard Cite

show abstract

“…It has been shown by several research groups that the stoichiometric composition, influenced by preparation conditions, changes the measured ionization energy. 15,25,27 In our own work in Ref. 27 Table S1 of the supplementary material.…”

Section: Measurements Of the Density Of States Of Perovskitesmentioning

confidence: 99%

“…15,25,27 In our own work in Ref. 27 Table S1 of the supplementary material. 31 The black curve marks a Gaussian fit to the data.…”

Section: Measurements Of the Density Of States Of Perovskitesmentioning

confidence: 99%

“…7, 8, 10-13, 16-26, and 28 which are used to relate Wf S and Wf P ; again, the detailed listing of values can be found in Table S1 of the supplementary material. 27 There is only a slight correlation between the two values, indicated by the shaded area; however, scattering of the data points is clearly dominant; for the same substrate material (e.g., PEDOT:PSS at Wf S = 5.1 eV) FIG 24 They showed that by tuning the precursor mixing ratio, the work function of MAPbI 3 on PEDOT:PSS could be changed from 4.8 eV (MAI rich) to 4 eV (PbI 2 rich) which was supported by theoretical calculations 42 predicting that Pb vacancies in an MAI rich film act as p-dopants which shift the Fermi energy downward while I vacancies in a PbI 2 rich film induce n-doping, thereby moving E F upward. (iii) Finally, if band bending occurs within the perovskite, then the value extracted for a thin film will differ from a thicker film.…”

Section: Influence Of the Substrate On The Perovskite Alignment mentioning

confidence: 99%

See 1 more Smart Citation

Research Update: The electronic structure of hybrid perovskite layers and their energetic alignment in devices

Olthof

2016

APL Materials

Self Cite

View full text Add to dashboard Cite

In recent years, the interest in hybrid organic–inorganic perovskites has increased at a rapid pace due to their tremendous success in the field of thin film solar cells. This area closely ties together fundamental solid state research and device application, as it is necessary to understand the basic material properties to optimize the performances and open up new areas of application. In this regard, the energy levels and their respective alignment with adjacent charge transport layers play a crucial role. Currently, we are lacking a detailed understanding about the electronic structure and are struggling to understand what influences the alignment, how it varies, or how it can be intentionally modified. This research update aims at giving an overview over recent results regarding measurements of the electronic structure of hybrid perovskites using photoelectron spectroscopy to summarize the present status.

show abstract

“…In a study by Emara et al, it has been pointed out that the ionization energy of MAPbI 3 determined by PES varies across a broad range of literature and can be connected to the composition of the perovskite film. 186 Prior to this study, it has been found that the core levels of the elemental components in MAPbI 3 shift substantially with prolonged X-ray exposure during XPS measurements. This X-ray induced degradation can lead to a shift in the Fermi level by more than 0.7 eV, such that initially p-type MAPbI 3 on NiO x becomes n-type.…”

Section: Influence Of Substrate On Band Positionsmentioning

confidence: 99%

Perovskite-Inspired Photovoltaic Materials: Toward Best Practices in Materials Characterization and Calculations

et al. 2017

View full text Add to dashboard Cite

ABSTRACT:Recently, there has been an explosive growth in research based on hybrid lead-halide perovskites for photovoltaics owing to rapid improvements in efficiency. The advent of these materials for solar applications has led to widespread interest in understanding the key enabling properties of these materials. This has resulted in renewed interest in related compounds and a search for materials that may replicate the defect-tolerant properties and long lifetimes of the hybrid lead-halide perovskites. Given the rapid pace of development of the field, the rises in efficiencies of these systems have outpaced the more basic understanding of these materials. Measuring or calculating the basic properties, such as crystal/electronic structure and composition, can be challenging because some of these materials have anisotropic structures, and/or are composed of both heavy metal cations and volatile, mobile, light elements. Some consequences are beam damage during characterization, composition change under vacuum, or compound effects, such as the alteration of the electronic structure through the influence of the substrate. These effects make it challenging to understand the basic properties integral to optoelectronic operation. Compounding these difficulties is the rapid pace with which the field progresses. This has created an ongoing need to continually evaluate best practices with respect to characterization and calculations, as well as to identify inconsistencies in reported values to determine if those inconsistencies are rooted in characterization methodology or materials synthesis. This article describes the difficulties in characterizing hybrid lead-halide perovskites and new materials, and how these challenges may be overcome. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 2 challenges discussed. The focus in this article is on crystallography, composition measurements, photoemission spectroscopy and calculations on perovskites and new, related absorbers. We suggest how some of the important artifacts could be avoided and how the reporting for each technique could be streamlined between groups to ensure reproducibility as the field progresses.

show abstract

Impact of Film Stoichiometry on the Ionization Energy and Electronic Structure of CH₃NH₃PbI₃ Perovskites

Cited by 157 publications

References 32 publications

Substrate-dependent electronic structure and film formation of MAPbI3 perovskites

Substrate-dependent electronic structure and film formation of MAPbI3 perovskites

Research Update: The electronic structure of hybrid perovskite layers and their energetic alignment in devices

Perovskite-Inspired Photovoltaic Materials: Toward Best Practices in Materials Characterization and Calculations

Contact Info

Product

Resources

About