Halide perovskite heterostructures offer promising interfacial interactions for energy conversion, yet challenges in synthesizing structurally well-defined systems limit detailed investigations into structure-property relationships. Here, we report the synthesis of compositionally controlled 3D/3D and 3D/2D halide perovskite heterostructures using evaporation crystallization-polymer pen lithography (EC-PPL) and single-particle analysis of their properties. By systematically varying A-site-cation combinations and crystal dimensions, we show that heterointerfaces induce local lattice distortions that modulate vibrational dynamics and electron-phonon coupling. These interfacial effects result in significantly extended carrier lifetimes compared to compositionally similar pure phases. Raman spectroscopy, temperature-dependent photoluminescence, and power-dependent emission analysis reveal that localized structural modulations at the interface govern exciton-phonon interactions. These effects are magnified in smaller crystals due to increased interfacial contributions. Our findings highlight the critical role of interface-driven lattice control in tuning the optoelectronic properties of halide perovskites and provide design principles for engineering heterostructures in next-generation optoelectronic devices.

Metastable nonradiative centers (supertraps) are significant energy loss channels in perovskite optoelectronic devices. In their active state, supertraps induce substantial energy loss through nonradiative recombination of free charge carriers. Transitions between active (energy loss) and passive (no energy loss) states result in photoluminescence (PL) blinking on timescales from milliseconds to seconds. The presence of blinking allowed us to investigate the active states of supertraps by extracting their time-dependent quenching efficiency functions on microsecond timescales from PL decay kinetics. These functions, unique to each supertrap, reveal how transitions from passive to active states modify the PL decay curve. Surprisingly, microcrystals often contain supertraps with different properties that effectively quench PL on different timescales relative to the excitation pulse: some start to quench the prompt PL immediately after excitation, while others effectively quench only the delayed PL after several microseconds. This leads to significant differences in PL blinking behavior when comparing prompt and delayed PL components. All these are inconsistent with the common view on the active state of a supertrap as a single deep energy level in the band gap. Instead, we suggest that the active state is a complex nonradiative center comprising a shallow and a deep energy level. These two-level centers likely form through the temporary association of individual defects, with variations in their quenching dynamics attributed to differences in energy levels, geometry, and local environment. By identifying supertraps with distinct time-dependent quenching dynamics, this work provides insights into defect engineering strategies that could reduce nonradiative losses in optoelectronic perovskite devices.

The illumination side of perovskite solar cells is more vulnerable to external impacts (such as hail, flying rocks, snow, hurricanes, etc.) than the rear side, leading to more likelihood of Pb2+ leakage. They also suffer from severe optical loss at the air/solid interface, deteriorating the solar cell performance. In this study, large-area textured phosphate-buffered functionalized polymer films (PFPFs) with self-healing characteristics, up to 16 x 16 cm2 in size, are deliberately designed and employed on the illumination side of PSCs. The PFPF immobilizes Pb2+ mainly through phosphate precipitation with an ultrafast Pb2+ sequestration rate (200.9 m2 min-1 g-1) and sequestration capacity equaling 24 times the theoretical Pb amount in typical 500-nm-thick PSCs. The pH-independent lead sequestration capability results in a Pb2+ leakage concentration well below the US drinking water safety level (15 mu g L-1) even under extreme environmental condition scenarios. The pyramidal-structured surface of the PFPF also reduces reflective losses over broadband wavelengths and increases the optical path of the incident light. We have utilized this in both rigid and flexible devices, improving the efficiencies by over 7% (relative gain). The PFPF is of low cost and can be easily applied to both rigid and flexible devices, demonstrating its universal applicability and promising commercialization potential.

Recently, research on the edge states of 2D lead halide perovskites (LHPs) has been attracting much attention. The lower‐energy edge state (LES) is believed to provide an efficient pathway for the dissociation of photoexcited excitons. However, the mechanism of the LES formation remains controversial, and studies that establish precisely the local electronic properties are lacking. Herein, the first study of spatially resolved electronic structures in 2D LHP single‐crystal flakes by X‐ray photoemission electron microscopy is presented, specifically identifying the contribution from the edge area. The results show that blueshifts occur in the Pb 5d core‐level peaks at the edge area compared to the interior area with much less difference in I 4d core‐level peaks. The shift becomes more pronounced as n varies from 1 to 3 (≈0.2–1.0 eV). This phenomenon is attributed to the surface restructuring of the edge area induced by the release of mechanical strain through lattice expansion. This work provides an important reference on the origin of the LES of 2D LHPs and is beneficial for future optoelectronic device applications.

Time-resolved analysis of photon cross-correlation function g(2)(τ) is applied to photoluminescence (PL) of individual submicrometer size MAPbI3 perovskite crystals. Surprisingly, an antibunching effect in the long-living tail of PL is observed, while the prompt PL obeys the photon statistics typical for a classical emitter. We propose that antibunched photons from the PL decay tail originate from radiative recombination of detrapped charge carriers which were initially captured by a very limited number (down to one) of shallow defect states. The concentration of these trapping sites is estimated to be in the range 1013-1016 cm-3. In principle, photon correlations can be also caused by highly nonlinear Auger recombination processes; however, in our case it requires unrealistically large Auger recombination coefficients. The potential of the time-resolved g(2)(0) for unambiguous identification of charge rerecombination processes in semiconductors considering the actual number of charge carries and defects states per particle is demonstrated.

The photoluminescence (PL) of metal halide perovskites can recover after light or current-induced degradation. This self-healing ability is tested by acting mechanically on MAPbI3 polycrystalline microcrystals by an atomic force microscope tip (applying force, scratching, and cutting) while monitoring the PL. Although strain and crystal damage induce strong PL quenching, the initial balance between radiative and nonradiative processes in the microcrystals is restored within a few minutes. The stepwise quenching-recovery cycles induced by the mechanical action is interpreted as a modulation of the PL blinking behavior. This study proposes that the dynamic equilibrium between active and inactive states of the metastable nonradiative recombination centers causing blinking is perturbed by strain. Reversible stochastic transformation of several nonradiative centers per microcrystal under application/release of the local stress can lead to the observed PL quenching and recovery. Fitting the experimental PL trajectories by a phenomenological model based on viscoelasticity provides a characteristic time of strain relaxation in MAPbI3 on the order of 10-100 s. The key role of metastable defect states in nonradiative losses and in the self-healing properties of perovskites is suggested.

The electrochemical nitrite sensors based on nanomaterials have attracted great attention because of their destructive effect on both environment and human health. Herein, gold nanoparticles modified molybdenum disulfide and reduced graphene oxide (AuNPs@MoS2/rGO) based nitrite sensor has been proposed combing a facile hydrothermal and chemical reduction methods. To optimize the electrochemical performances, the as-fabricated AuNPs@MoS2/rGO sensors with different contents of gold have been systematic investigated toward nitrite detection by cyclic voltammograms and amperometry techniques. The measured results demonstrated that the as-prepared Au(4.5)NPs@MoS2/rGO sensor exhibits high sensitivity (0.805 mu A mu M-1.cm(-2)), short response time (3 s), low detection limit (0.038 mu M (S/N = 3)) and good linear detection range (0.2 mu M-2600 mu M). Meanwhile, it also displays excellent selectivity and good long-term stability toward nitrite. Finally, the excellent electrochemical performances of Au(4.5)NPs@MoS2/rGO nitrite sensor not only can be attributed to the synergistic effect between MoS2 and rGO nanosheets, but also ascribed to the excellent catalytic property of suitable content of Au nanoparticles.

The ancient technology of colouring by mechanical rubbing of a dry pigment onto surfaces can be applied to metal halide perovskites, enabling the fabrication of highly luminescent templated micro and nano arrays.

Antibunching effect is typically observed in individual systems possessing photoluminescence (PL) blinking and vice versa. Contrary to this common perception, absence of antibunching in strongly blinking methyl ammonium led tri-iodide (MAPbI(3)) perovskite crystals of sizes from tens to hundreds of nanometers regardless of the excitation power density is observed. Antibunching effect does not appear even when photon statistics are analyzed for bright and intermediate PL intensity levels independently. This shows that there is no directional energy funneling and accumulation of charge carriers in the small local regions in MAPbI(3) crystals where an Auger recombination can potentially suppress the simultaneous emission of two photons. This result allows for the exclusion of the PL blinking mechanism based on the idea of emitting sites previously hypothesized for perovskites. Therefore, the model of PL blinking in perovskite crystals based on the presence of a metastable non-radiative recombination center (the supertrap) is the only one proposed so far which explains blinking without conflicting with the absence of photon correlations.

Metal halide perovskites are an important class of emerging semiconductors. Their charge carrier dynamics is poorly understood due to limited knowledge of defect physics and charge carrier recombination mechanisms. Nevertheless, classical ABC and Shockley-Read-Hall (SRH) models are ubiquitously applied to perovskites without considering their validity. Herein, an advanced technique mapping photoluminescence quantum yield (PLQY) as a function of both the excitation pulse energy and repetition frequency is developed and employed to examine the validity of these models. While ABC and SRH fail to explain the charge dynamics in a broad range of conditions, the addition of Auger recombination and trapping to the SRH model enables a quantitative fitting of PLQY maps and low-power PL decay kinetics, and extracting trap concentrations and efficacies. However, PL kinetics at high power are too fast and cannot be explained. The proposed PLQY mapping technique is ideal for a comprehensive testing of theories and applicable to any semiconductor. Charge dynamics in perovskite is not well-understood, limited by the knowledge of defect physics and charge recombination mechanism, yet the ABC and SRH models are widely used. Here, the authors introduce advanced PLQY mapping as function of excitation pulse energy and repetition frequency to examine the validity of these models.

Metal halide perovskites show great promise for a wide range of optoelectronic applications but are plagued by instability when exposed to air and light. This work presents low-temperature solution growth of vertically aligned CsPbBr3 nanowire arrays in AAO (anodized aluminum oxide) templates with excellent stability, with samples exposed to air for 4 months still exhibiting comparable photoluminescence and UV stability to fresh samples. The single-crystal nanowire length is adjusted from ∼100 nm to 5 μm by adjusting the precursor solution amount and concentration, and we observe length-to-diameter ratios as high as 100. Structural characterization results indicate that large-diameter CsPbBr3 nanowires have an orthorhombic structure, while the 10 nm- and 20 nm-diameter nanowires adopt a cubic structure. Photoluminescence shows a gradual blue-shift in emission with decreasing nanowire diameter and marginal changes under varying illumination power intensity. The CsPbBr3-nanowires/AAO composite exhibits excellent resistance to X-ray radiation and long-term air storage, which makes it promising for future optoelectronic applications such as X-ray scintillators. These results show how physical confinement in AAO can be used to realize CsPbBr3 nanowire arrays and control their morphology and crystal structure.

Molecular additives are widely utilized to minimize non-radiative recombination in metal halide perovskite emitters due to their passivation effects from chemical bonds with ionic defects. However, a general and puzzling observation that can hardly be rationalized by passivation alone is that most of the molecular additives enabling high-efficiency perovskite light-emitting diodes (PeLEDs) are chelating (multidentate) molecules, while their respective monodentate counterparts receive limited attention. Here, we reveal the largely ignored yet critical role of the chelate effect on governing crystallization dynamics of perovskite emitters and mitigating trap-mediated non-radiative losses. Specifically, we discover that the chelate effect enhances lead-additive coordination affinity, enabling the formation of thermodynamically stable intermediate phases and inhibiting halide coordination-driven perovskite nucleation. The retarded perovskite nucleation and crystal growth are key to high crystal quality and thus efficient electroluminescence. Our work elucidates the full effects of molecular additives on PeLEDs by uncovering the chelate effect as an important feature within perovskite crystallization. As such, we open new prospects for the rationalized screening of highly effective molecular additives.

The fate of excited charge carriers in metal halide perovskite semiconductors is influenced by energetic disorder and defects. Here, photoluminescence (PL) blinking is used to probe metastable nonradiative (NR) centers and the nanoscale energy landscape. Temporal activation of an NR center creates a local region with increased NR recombination. Activation and deactivation of this local PL quenching does not only lead to PL blinking, but also to fluctuations of the PL spectra, if the crystal is inhomogeneous in the sense that the PL emission spectrum is slightly different from one location to another. It resembles the spectral hole‐burning technique; however, here the eliminated excited states are chosen by their spatial localization close to the quencher. In MAPbI 3 , PL spectral fluctuations at low temperature reveal energetic inhomogeneities on the order of 5 to 10 meV. Quenching of the main PL band is often found to correlate with an increase of the low‐energetic tail of the PL spectra, which is attributed to partially radiative recombination of charges captured by the NR center. The transition energy of the NR center is found to be only ≈80 meV smaller than the bandgap, implying that the underlying defect cannot be a single mid‐bandgap state.

Organo-metal-halide (OMH) perovskites form a new class of materials withperovskite crystal structure ABX3 where A is an organic molecule, B is lead (Pb)and X is a halide atom (I or Br). OMH perovskite semiconductors have been widely used in photovoltaics due to their very strong absorption of sun light, very suitable electrical properties, and the ease of preparation. Today the power conversion efficiency of record devices based on OMH is as large as 25.5%.There are still many challenges for commercial application of OMH perovskitebased solar cells and other devices. One of the problems we can formulate assensitivity of the properties of OMP semiconductors and devices based on them on factors like electric field, atmosphere, light, temperature and so on. Despite large efforts spent in the scientific community on investigation of the environmental effects on OMH perovskites and stability of devices many issues are still not wellunderstood.In this thesis, I present results of several research projects where photoluminescence (PL) properties of OMH perovskites were studied by optical luminescence microscopy and spectroscopy under different environmental conditions such as humidity, electric field, local pressure and low temperature. We observed that water molecules can play an important role in the transformation of OMH perovskite from its intermediate phase containing solvent molecules to the perovskite crystal structure. We found that both electric field and local pressure and mechanical damage at nano-scale can create temporal PL quenching in OMH perovskites microand nanocrystals. We propose that PL quenching is induced by deep defects states created by electric field, pressure or mechanical manipulation. However, the destructive influence of all these factors on PL disappears several minutes after the influence was stopped due to self-healing properties of OHP. By comparing PL spectra and PL intensity and cryogenic temperatures and at room temperature we found that the concentration of shallow defect states and deep defect states are proportional to each other. (Less)

Photoluminescence (PL) blinking is a common phenomenon in nanostructured semiconductors associated with charge trapping and defect dynamics. PL blinking kinetics exhibit very broadly distributed timescales. The traditionally employed analysis of probability distribution of ON and OFF events suffers from ambiguities in their determination in complex PL traces making its suitability questionable. Here, the statistically correct power spectral density (PSD) estimation method applicable for fluctuations of any complexity is employed. PSDs of the blinking traces of submicrometer MAPbI 3 crystals at high frequencies follow power law with excitation power density dependent parameters. However, at frequencies less than 0.3 Hz, the majority of the PSDs saturate revealing the presence of a maximal characteristic timescale of blinking in the range of 0.5–10 s independently of the excitation power density. Super‐resolution optical microscopy shows the characteristic timescale to be an inherent material property independent of polycrystallinity. Thus, for the first time the maximum timescale of the multiscale blinking behavior of nanoparticles is observed demonstrating that the power law statistics are not universal for semiconductors. It is proposed that the viscoelasticity of metal‐halide perovskites can limit the maximum timescale for the PL fluctuations by limiting the memory of preceded deformations/re‐arrangements of the crystal lattice.

Nonradiative losses in semiconductors are related to defects. At cryogenic temperatures, defect-related photoluminescence (PL) at energies lower than the band-edge PL is observed in methylammonium lead triiodide perovskite. We applied multispectral PL imaging to samples prepared by two different procedures and exhibiting 1 order of magnitude different PL quantum yield (PLQY). The high-PLQY sample showed concentration of the emitting defect sites around 10(12)-10(13) cm(-3). No correlation between PLQY and the relative intensity of the defect emission was found when micrometer-sized local regions of the same sample were compared. However, a clear positive correlation between the lower PLQY and higher defect emission was observed when two preparation methods were contrasted. Therefore, although the emissive defects are not connected directly with the nonradiative centers and may be spatially separated at the nano scale, chemical processes during the perovskite synthesis promote/prevent formation of both types of defects at the same time.

Metal halide perovskites are promising optoelectronic materials. Their electronic properties however are rather unstable which is often assigned to ion migration. Ion migration can be readily influenced by an electric field (EF). Here, the response of photoluminescence (PL) of individual MAPbX 3 (MA = CH 3 NH 3 , X = I, Br) sub‐micrometer‐sized polycrystals to EF is studied. Alternating EF with frequency higher than 10 Hz is found to reversibly quench PL. It is proposed that an alternating EF when applied together with light increases ion migration. This leads to a shift in the equilibrium between creation and annihilation of defects toward higher concentration of nonradiative recombination centers. The PL quenching is found to increase with increasing frequency of the field. This can be rationalized by the frequency dependence of the dielectric constant, leading to stronger internal fields for high modulation frequencies compared to, e.g., a constant EF with the same external amplitude. PL quenching and enhancement observed under constant EF are hypothesized to be due to a reconfiguration of already existing nonradiative recombination centers situated on grain boundaries. The control of perovskite PL by alternating EF reported here can find applications in optoelectronic devices.

Photoluminescence (PL) of CH3NH3PbI3 perovskites depends strongly on sample preparation, atmosphere, crystal size, and so forth. However, the origin of these dependencies is always misunderstood because of the co-works of many different factors. Herein, we prepared hexagonal-shaped single crystals with tens of micrometers in size and observed a red-shifted PL emission (800-830 nm) mainly from the crystal edges besides the usual band-to-band transition (760 nm) from the central regions. Also, significantly different time-resolved dynamics and excitation power dependencies were observed. To summarize, we conclude that the red-shifted component comes from the depth of the crystal, where monomolecular recombination occurs involving photogenerated charges and unintentional doped charges, while the normal PL is emitted by bimolecular recombination from the surface layers. These results showed the significance of pure optical effects in perovskite crystals and would promote detailed understanding of the charge dynamics and recombination in perovskite crystalline materials of different geometries and sizes.