Photoinduced degradation of methylammonium lead triiodide perovskite semiconductors

Tang, Xiaofeng; Brandl, Marco; May, B. D.; Levchuk, Ievgen; Hou, Yi; Richter, Moses; Chen, Haiwei; Chen, Shi; Kahmann, Simon; Osvet, Andres; Maier, Florian; Steinrück, Hans‐Peter; Hock, Rainer; Matt, Gebhard J.; Brabec, Christoph J.

doi:10.1039/c6ta06497c

Cited by 136 publications

(129 citation statements)

References 37 publications

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“…The combination of reduced grain size throughout the film and a higher defect density serve as the cause for a lower fill factor (FF) and short-circuit current density (J SC ) in sol-eng devices, resulting in a lower overall efficiency. [18,20,48] This observation and our measurements of the local temperature demonstrate that light induced heating effects alone do not result in a degradation of the perovskite film on this timescale and the observed degradation is a consequence of exposure to light and oxygen. [42,45,46] For the PbAc 2 recipe, the inherent water in the precursor solution as well as the addition of hypophosphorous acid results in an enlargement of the grain size and improved film morphology resulting in perovskite films with high electronic quality and low defect density.…”

Section: Photovoltaic Performancesupporting

confidence: 57%

Role of Microstructure in Oxygen Induced Photodegradation of Methylammonium Lead Triiodide Perovskite Films

Sun

Faßl

Becker‐Koch

et al. 2017

Advanced Energy Materials

203

210

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photovoltaic technology, where lifetimes greater than 25 years are required. [2] Although the issue of device stability has attracted increased attention of the photovoltaic research community in the last two years, reports that systematically study the fundamental causes (e.g., heat, electrical stress, humidity, oxygen, (UV) light, chemical precursors, processing conditions, influence of film quality and morphology) and mechanisms limiting the material and device stability remain scarce. [2][3][4][5] While the degradation of methylammonium lead iodide (MAPbI 3 ) in humid air has been studied experimentally as well as theoretically and was long thought to be the main factor for material degradation in ambient environment, [6][7][8][9][10][11][12][13][14][15] studies exploring the influence of oxygen and light on the solar cell performance have only recently been reported. [16][17][18][19][20] It has been shown that photoexcited electrons in the perovskite layer can form superoxide (O 2 − ) via electron transfer to molecular oxygen, which through deprotonation of the methylammonium cation in turn results in irreversible material degradation. The severity of the degradation has been linked to the efficiency of electron extraction via the electron extracting layer (EEL): devices employing a compact-TiO 2 /mesoporous Al 2 O 3 or compact-TiO 2 as EELs degraded in dry air on a timescale of less than 1 h, while with the use of a mesoporous TiO 2 layer, an EEL which results in faster electron extraction, the lifetimes were significantly increased. However, in these reports only the degradation of complete photovoltaic device was reported, with limited information on the degradation of the perovskite active layer itself and the impact of its microstructure was not identified.In this work, we systematically study the degradation of MAPbI 3 films under precisely controlled exposure to various oxygen levels (0-20%) under simulated sunlight in order to shed light on the progression of perovskite degradation under these conditions. We investigate two types of perovskite layers that are formed using different fabrication methods. The two recipes allow us to include the effect of layer microstructure on the dynamics of oxygen-induced degradation. We characterize the electronic, optical, compositional, and structural properties of the degraded perovskite films and correlate these results This paper investigates the impact of microstructure on the degradation rate of methylammonium lead triiodide (MAPbI 3 ) perovskite films upon exposure to light and oxygen. By comparing the oxygen induced degradation of perovskite films of different microstructure-fabricated using either a lead acetate trihydrate precursor or a solvent engineering technique-it is demonstrated that films with larger and more uniform grains and better electronic quality show a significantly reduced degradation compared to films with smaller, more irregular grains. The effect of degradation on the optical, compositional, and microstructural properties of the perovsk...

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Section: Photovoltaic Performancesupporting

confidence: 57%

Role of Microstructure in Oxygen Induced Photodegradation of Methylammonium Lead Triiodide Perovskite Films

Sun

Faßl

Becker‐Koch

et al. 2017

Advanced Energy Materials

203

210

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“…Several groups observed significant photoinstabilities of MAPbI 3 . However, most experiments were performed in air.…”

Section: Perovskite Degradationmentioning

confidence: 94%

Influence of Radiation on the Properties and the Stability of Hybrid Perovskites

et al. 2017

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Organic-inorganic perovskites are well suited for optoelectronic applications. In particular, perovskite single and perovskite tandem solar cells with silicon are close to their market entry. Despite their swift rise in efficiency to more than 21%, solar cell lifetimes are way below the needed 25 years. In fact, comparison of the time when the device performance has degraded to 80% of its initial value (T lifetime) of numerous solar cells throughout the literature reveals a strongly reduced stability under illumination. Herein, the various detrimental effects are discussed. Most notably, moisture- and heat-related degradation can be mitigated easily by now. Recently, however, several photoinduced degradation mechanisms have been observed. Under illumination, mixed perovskites tend to phase segregate, while, further, oxygen catalyzes deprotonation of the organic cations. Additionally, during illumination photogenerated charge can be trapped in the NH antibonding orbitals causing dissociation of the organic cation. On the other hand, organic-inorganic perovskites exhibit a high radiation hardness that is superior to crystalline silicon. Here, the proposed degradation mechanisms reported in the literature are thoroughly reviewed and the microscopic mechanisms and their implications for solar cells are discussed.

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“…Using x-ray photoelectron spectroscopy (XPS), we observed no significant traces of oxygen (O 1s) in the PTEAI-capped film, even after 640 minutes of accelerated aging tests (Figure 5b), revealing that the PTEAI-capped MAPbI3 inhibits the formation of an oxygen-containing compounds, 51 and increases film stability. In contrast, we found that the amount of oxygencontaining compounds 51 in bare MAPbI3 increases within 460 minutes, which can be attributed to a PbOx compound. 51,52 The presence of the oxygen in fresh bare MAPbI3 indicating surface contamination from atmospheric oxygen is significantly higher than in fresh PTEAI-capped samples.…”

Section: Protection Mechanisms In Top-performing Candidatesmentioning

confidence: 99%

How machine learning can help select capping layers to suppress perovskite degradation

Hartono¹,

Thapa²,

Tiihonen³

et al. 2020

Preprint

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Environmental stability of perovskite solar cells (PSCs) can be improved by a thin layer of low-dimensional (LD) perovskite sandwiched between the perovskite absorber and the hole transport layer (HTL). This layer, called ‘capping layer,’ has mostly been optimized by trial and error. In this study, we present a machine-learning framework to rationally design and optimize perovskite capping layers. We ‘featurize’ 21 organic halide salts, apply them as capping layers onto methylammonium lead iodide (MAPbI3) thin films, age them under accelerated conditions combining illumination and increased humidity and temperature, and determine features governing stability using random forest regression and SHAP (SHapley Additive exPlanations). We find that a low number of hydrogen-bonding donors and a small topological polar surface area of the organic molecules correlate with increased MAPbI3 film stability. The top performing organic halide salt, phenyltriethylammonium iodide (PTEAI), successfully extends the MAPbI3 stability lifetime by 4±2 times over bare MAPbI3 and 1.3±0.3 times over state-of-the-art octylammonium bromide (OABr). Through morphological and synchrotron-based structural characterization, we found that this capping layer consists of a Ruddlesden-Popper perovskite structure and stabilizes the photoactive layer by “sealing off” the grain boundaries and changing the lead surface chemistry, through the suppression of lead (II) iodide (PbI2) formation and methylammonium loss.

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Photoinduced degradation of methylammonium lead triiodide perovskite semiconductors

Cited by 136 publications

References 37 publications

Role of Microstructure in Oxygen Induced Photodegradation of Methylammonium Lead Triiodide Perovskite Films

Role of Microstructure in Oxygen Induced Photodegradation of Methylammonium Lead Triiodide Perovskite Films

Influence of Radiation on the Properties and the Stability of Hybrid Perovskites

How machine learning can help select capping layers to suppress perovskite degradation

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