23 research outputs found
Microscopic insight into the reversibility of photodegradation in MAPbI3 thin films
No full textWhether optoelectronic devices based on metal-halide perovskite semiconductors will become a commercially viable technology will be determined by their intrinsic and operational stability. Recent results indicate there is some reversibility of perovskite degradation in thin films and devices, although mechanistic insight into the processes driving degradation and recovery are still scarce. We here present a comparative spectroscopic study of methylammonium lead iodide (MAPbI3) films having undergone either photo- or thermal degradation under controlled conditions. We confirm that the degradation mechanism pertaining to each type of stress is inherently different. Our results from photoluminescence microscopy measurements paint a spatially, spectrally and temporarily resolved picture showing that, unlike thermally degraded samples, photodegraded samples are in a state that intermittently recovers to luminescent MAPbI3 upon laser excitation. This indicates that rather than irreversibly decomposing, photoinduceddegradation leaves MAPbI3 structurally or compositionally intact but induces defects causing non-radiative recombination losses
Microscopic insight into the reversibility of photodegradation in MAPbI3 thin films
No full textWhether optoelectronic devices based on metal-halide perovskite semiconductors will become a commercially viable technology will be determined by their intrinsic and operational stability. Recent results indicate there is some reversibility of perovskite degradation in thin films and devices, although mechanistic insight into the processes driving degradation and recovery are still scarce. We here present a comparative spectroscopic study of methylammonium lead iodide (MAPbI3) films having undergone either photo- or thermal degradation under controlled conditions. We confirm that the degradation mechanism pertaining to each type of stress is inherently different. Our results from photoluminescence microscopy measurements paint a spatially, spectrally and temporarily resolved picture showing that, unlike thermally degraded samples, photodegraded samples are in a state that intermittently recovers to luminescent MAPbI3 upon laser excitation. This indicates that rather than irreversibly decomposing, photoinduced degradation leaves MAPbI3 structurally or compositionally intact but induces defects causing non-radiative recombination losses
Spatially-resolved nanoscale measurements of grain boundary enhanced photocurrent in inorganic CsPbBr3 perovskite films
No full textInfluence of Oxygen Ion Migration from Substrates on Photochemical Degradation of CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> Hybrid Perovskite
No full textMeasurements of XPS survey, core levels (N 1s, O 1s, Pb 4f, I 3d), and valence band (VB) spectra of CH3NH3PbI3 (MAPbI3) hybrid perovskite prepared on different substrates (glass, indium tin oxide (ITO), and TiO2) aged under different light-soaking conditions at room temperature are presented. The results reveal that the photochemical stability of MAPbI3 depends on the type of substrate and gradually decreases when glass is replaced by ITO and TiO2. Also, the degradation upon exposure to visible light is accompanied by the formation of MAI, PbI2, and Pb0 products as shown by XPS core levels spectra. According to XPS O 1s and VB spectra measurements, this degradation process is superimposed on the partial oxidation of lead atoms in ITO/MAPbI3 and TiO2/MAPbI3, for which Pb–O bonds are formed due to the diffusion of the oxygen ions from the substrates. This unexpected interaction leads to additional photochemical degradation
Efficient and Stable MAPbI3Based Perovskite Solar Cells Using Polyvinylcarbazole Passivation
No full textReversible and Irreversible Electric Field Induced Morphological and Interfacial Transformations of Hybrid Lead Iodide Perovskites
No full textFilm Deposition Techniques Impact the Defect Density and Photostability of MAPbI3 Perovskite Films
No full text
γ‑Ray-Induced Degradation in the Triple-Cation Perovskite Solar Cells
No full textWe
report on the impact of γ radiation (0–500 Gy)
on triple-cation Cs0.15MA0.10FA0.75Pb(Br0.17I0.83)3 perovskite solar
cells. A set of experiments was designed to reveal the individual
contributions of the hole-collecting bottom electrode, perovskite
absorber, and electron transport layer (ETL) to the overall solar
cell degradation under radiation exposure. We show that the glass/ITO/PEDOT:PSS
hole-collecting electrode withstands a 500 Gy dose without any losses
in the solar cell performance. In contrast, the perovskite absorber
films and PC61BM ETL are very sensitive to γ rays,
as can be concluded from the radiation-induced decay of the solar
cell efficiency by ∼32–41%. Red shift of the perovskite
emission bands and strong enhancement of the photoluminescence suggest
that γ rays induce phase segregation of iodine-rich and bromine-rich
domains, which represents the first reported example of the radiation-induced
halide phase separation in perovskite films. The degradation pathway
revealed here emphasizes the need for developing a new generation
of metal halide absorbers and ETL materials with improved radiation
stability to enable potential space applications of perovskite photovoltaics
Comparative Intrinsic Thermal and Photochemical Stability of Sn(II) Complex Halides as Next-Generation Materials for Lead-Free Perovskite Solar Cells
No full textHere, we present
a systematic study of the thermal and photochemical
degradation pathways for a series of complex tin-based halides ASnX3 (X = I, Br) with organic (CH3NH3+, H2NCHNH2+) and inorganic
(Cs+) univalent A-site cations. Thin films of tin-based
perovskites were exposed to continuous light soaking and/or thermal
annealing in the dark under an inert atmosphere, which simulate pragmatic
anoxic operation conditions of solar cells with the absorber layer
isolated from the (re)action of oxygen and moisture by appropriate
encapsulation. Using a set of complementary techniques such as optical
spectroscopy, atomic force microscopy, X-ray diffraction, and X-ray
photoelectron spectra, we have elucidated that hybrid tin halide perovskites
undergo rapid thermal and light-induced degradation with the complete
elimination of organic cations and the formation of some volatile
decomposition products and Sn(IV) halide species. On the contrary,
all-inorganic compositions comprising CsSnBr3 and, particularly,
CsSnI3 showed a much superior thermal and photochemical
stability with respect to both light and elevated temperatures. Unfortunately,
all investigated complex tin halides suffer from heat- and light-induced
Sn(II) disproportionation with the formation of Sn(IV) species and,
presumably, metallic Sn0. This facile disproportionation
and chemical degradation pathway reduces dramatically the intrinsic
stability of Sn(II) complex halides and limits their potential for
practical applications. While this problem can be addressed using
additional stabilizing additives and crystal-lattice-engineering approaches,
the analysis of the comprehensive sets of our results solidifies further
rational design approaches for the development of lead-free absorbers
for inorganic perovskite-based solar cells with enhanced stability
for efficient and durable photovoltaic systems
