Electronic Level Alignment in Inverted Organometal Perovskite Solar Cells

Schulz, Philip; Whittaker‐Brooks, Luisa; MacLeod, Bradley A.; Olson, Dana C.; Loo, Yueh Lin; Kahn, Antoine

doi:10.1002/admi.201400532

Cited by 188 publications

(251 citation statements)

References 24 publications

Supporting

Mentioning

226

Contrasting

Order By: Relevance

“…This procedure changes the polarization of the device to a state in which higher efficiency values can sometimes be inferred from J–V measurements than compared with short circuit or reverse bias preconditioning13. To explore this effect we have used two preconditions in this study: short circuit dark conditions ( V preset =0 V) where the device is polarized by the built-in potential between the contacts ( V bi ∼0.9–1.3)414243, or an applied forward bias ( V preset =1 or 1.2 V), which significantly reduces the potential, and thus the device polarization, between contacts. These two states form the starting conditions for the subsequent transient measurements.…”

Section: Resultsmentioning

confidence: 99%

Evidence for ion migration in hybrid perovskite solar cells with minimal hysteresis

et al. 2016

View full text Add to dashboard Cite

Ion migration has been proposed as a possible cause of photovoltaic current–voltage hysteresis in hybrid perovskite solar cells. A major objection to this hypothesis is that hysteresis can be reduced by changing the interfacial contact materials; however, this is unlikely to significantly influence the behaviour of mobile ionic charge within the perovskite phase. Here, we show that the primary effects of ion migration can be observed regardless of whether the contacts were changed to give devices with or without significant hysteresis. Transient optoelectronic measurements combined with device simulations indicate that electric-field screening, consistent with ion migration, is similar in both high and low hysteresis CH3NH3PbI3 cells. Simulation of the photovoltage and photocurrent transients shows that hysteresis requires the combination of both mobile ionic charge and recombination near the perovskite-contact interfaces. Passivating contact recombination results in higher photogenerated charge concentrations at forward bias which screen the ionic charge, reducing hysteresis.

show abstract

Section: Resultsmentioning

confidence: 99%

Evidence for ion migration in hybrid perovskite solar cells with minimal hysteresis

et al. 2016

View full text Add to dashboard Cite

show abstract

“…Due to the possibility for evaporation, the fullerene C 60 was mostly chosen instead of PCBM which is more commonly used in solar cell devices. Using UPS and IPES measurements, Schulz et al 22 found flat band conditions and a good alignment between the lowest unoccupied molecular orbital (LUMO) of C 60 and the CB of MAPbI 3 with a mere injection barrier of 100 meV, as shown in Fig. 6(a).…”

Section: Energetic Alignment To Organic Transport Layersmentioning

confidence: 90%

“…This implies that the substrate is, to some degree, able to control the band alignment of MAPbI 3 , at least for the relatively thin layer thicknesses investigated here. In a different study, Schulz et al 22 compared thick layers of MAPbI 3 on the high Wf material NiO (Wf S = 4.9 eV) and the low Wf TiO 2 (Wf S = 4 eV). They found a change in perovskite Wf of 700 meV, corresponding to a shift from a mid-gap Fermi energy position on the p-type NiO to a position close to the CB for n-type However, the perovskite showed an opposing trend with a lower Wf value of Wf P = 4.0 eV on the SnO 2 compared to the one on TiO 2 (Wf P = 4.13 eV).…”

Section: Influence Of the Substrate On The Perovskite Alignment mentioning

confidence: 99%

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

Olthof

2016

APL Materials

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

“…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. 178 X-ray photon induced degradation of MAPbI 3 on TiO 2 under an ultrahigh vacuum of 2×10 -10 Torr was recently studied in detail by Steirer et al 187 It was found that under a constant X-ray photon flux density of 1.5×10 11 photons cm -2 s -1 , the methylammonium cation deprotonated and was lost, as shown in Figure 10. At the same time, the iodide content reduced exponentially over time, leading to the MAPbI 3 converting back to PbI 2 .…”

Section: Influence Of Substrate On Band Positionsmentioning

confidence: 98%

“…A significant refinement of the band onset determination for a range of hybrid perovskite films was reported by Endres et al Therein, the electrical bandgap for MAPbI 3 was determined to be 1.6±0.1 eV, 177 in agreement with optical measurements, 175 and demonstrating greater accuracy than previous electronic bandgap measurements that did not make use of DOS fitting of the IPES spectra. 163,178 In the same way, the bandgaps and band offsets have been determined for MAPbBr 3 and CsPbBr 3 compounds. 177 It is important to note that the optical bandgap determined from optical characterization is prone to its own set of measurement and analysis errors.…”

Section: Complementary Techniques To Photoemission Spectroscopymentioning

confidence: 99%

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

et al. 2017

Self Cite

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

Electronic Level Alignment in Inverted Organometal Perovskite Solar Cells

Cited by 188 publications

References 24 publications

Evidence for ion migration in hybrid perovskite solar cells with minimal hysteresis

Evidence for ion migration in hybrid perovskite solar cells with minimal hysteresis

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