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The utilization of mixed cations is beneficial for taking the advantages of cations and achieving highly efficient perovskite solar cells (PSCs). Herein, the precisely small incorporation of CH(NH2)2 (FA) cations in methyl ammonium lead iodide (MAPbI3) enables the formation of compact, smooth perovskite film with high crystallinity. Consequently, the short-circuit current and the fill factor of the PSCs based on FAxMA1-xPbI3 perovskite are greatly improved, leading to the enhanced device efficiency. The champion PSC based on FA0.1MA0.9PbI3 exhibits a remarkably high efficiency of 22.02%. Furthermore, the PSCs based on FA0.1MA0.9PbI3 perovskite also show improved device stability. This work provides a simple approach to fabricate high-quality perovskite films and high-performance PSCs with better stability.

The conventional strategy of synthetic colloidal chemistry for bright and stable quantum dots has been the production of epitaxially matched core/shell heterostructures to mitigate the presence of deep trap states. This mindset has been shown to be incompatible with lead halide perovskite nanocrystals (LHP NCs) due to their dynamic surface and low melting point. Nevertheless, enhancements to their chemical stability are still in great demand for the deployment of LHP NCs in light-emitting devices. Rather than contend with their attributes, we propose a method in which we can utilize their dynamic, ionic lattice and uniquely defect-tolerant band structure to prepare non-epitaxial salt-shelled heterostructures that are able to stabilize these materials against their environment, while maintaining their excellent optical properties and increasing scattering to improve out-coupling efficiency. To do so, anchored LHP NCs are first synthesized through the heterogeneous nucleation of LHPs onto the surface of microcrystalline carriers, such as alkali halides. This first step stabilizes the LHP NCs against further merging, and this allows them to be coated with an additional inorganic shell through the surface-mediated reaction of amphiphilic Na and Br precursors in apolar media. These inorganically shelled NC@carrier composites offer significantly improved chemical stability toward polar organic solvents, such as γ-butyrolactone, acetonitrile, N-methylpyrrolidone, and trimethylamine, demonstrate high thermal stability with photoluminescence intensity reversibly dropping by no more than 40% at temperatures up to 120 °C, and improve compatibility with various UV-curable resins. This mindset for LHP NCs creates opportunities for their successful integration into next-generation light-emitting devices., ACS Nano, 13 (10), ISSN:1936-0851, ISSN:1936-086X

Metal-halide perovskite semiconductors have attracted intense interest over the past decade, particularly for applications in photovoltaics. Low-energy optical phonons combined with significant crystal anharmonicity play an important role in charge-carrier cooling and scattering in these materials, strongly affecting their optoelectronic properties. We have observed optical phonons associated with Pb–I stretching in both MAPbI3 single crystals and polycrystalline thin films as a function of temperature by measuring their terahertz conductivity spectra with and without photoexcitation. An anomalous bond hardening was observed under above-bandgap illumination for both single-crystal and polycrystalline MAPbI3. First-principles calculations reproduced this photo-induced bond hardening and identified a related lattice contraction (photostriction), with the mechanism revealed as Pauli blocking. For single-crystal MAPbI3, phonon lifetimes were significantly longer and phonon frequencies shifted less with temperature, compared with polycrystalline MAPbI3. We attribute these differences to increased crystalline disorder, associated with grain boundaries and strain in the polycrystalline MAPbI3. Thus we provide fundamental insight into the photoexcitation and electron–phonon coupling in MAPbI3.

The main drawback of the methylammonium lead halide perovskite solar cells is their degradation in ambient atmosphere. To investigate ambient-air-induced cell degradation, spec-tral dependencies of open-circuit voltage (VOC), fill factor (FF) and the power conversion effi-ciency (PCE) have been acquired (for the first time reported in literature). Our custom-made measurement system allowed us to perform measurements of the above-mentioned entities in situ directly in vacuum during and after thermal deposition of the elec-trode. We also studied how these parameters in vacuum changed after cell exposure to ambient air for 85 min (50 nm top electrode) and for 180 min (100 nm top Ag electrode). For fresh CH3NH3PbI3–xClx cell (never been in open air) with very high shunt resistance of 3·107 Ω·cm2 (with practically no shorts and therefore FF could be determined mainly by charge carrier recombination processes) we found that FF in vacuum increased along with an increase of the incident photon energy from 0.55 at 760 nm up to 0.82 at 400 nm. Hypothesis considering hot polaron participation in charge carrier photogeneration and recombination processes as well as another competing hypothesis were offered as possible explanations for the observed FF increase. The kinetics of short-circuit photocurrent EQE with a change in pressure was also inves-tigated. It was also shown that perovskite solar cell degradation could be noticeably reduced by increasing the top Ag electrode thickness to at least 100 nm, which could possibly facilitate the usual encapsulation process.---//---This work is licensed under a CC BY 4.0 license., Institute of Solid State Physics, University of Latvia as the Centre of Excellence has received funding from the European Union’s Horizon 2020 Framework Pro-gramme H2020-WIDESPREAD-01-2016-2017-Teaming Phase2 under grant agreement No. 739508, project CAMART²

Development of hybrid organic-inorganic perovskite solar cells (PSC) has been one of the hottest research topics since 2013. Within brief literature review, we would like to achieve two objectives. Firstly, we would like to indicate that a whole set of physical properties, such as high change carrier mobility, very low recombination rates, large carrier life time and diffu-sion length, large absorption coefficients and very weak exciton binding energies, are defining high power conversion efficiency (PCE) of methyl ammonium lead trihalide SC. The second objective is to draw attention to some, in our opinion, important aspects that previously have not been satisfactory addressed in literature. Although degradation of PSC is widely discussed, processes at very first exposure to ambient conditions after deposition of top electrode are uncovered.---//---This work is licensed under a CC BY 4.0 license., Institute of Solid State Physics, University of Latvia as the Centre of Excellence has received funding from the European Union’s Horizon 2020 Framework Pro-gramme H2020-WIDESPREAD-01-2016-2017-Teaming Phase2 under grant agreement No. 739508, project CAMART².

The preparation of strongly emissive CsPbBr3perovskite nanocrystals with robust surface passivation is a challenge in the field of lead halide perovskite nanomaterials. We report an approach to prepare polymer-capped CsPbBr3perovskite nanocrystals by reacting oleylammonium/oleate-capped Cs4PbBr6nanocrystals with poly(maleic anhydride-alt-1-octadecene) (PMAO). PMAO contains succinic anhydride units that are reactive towards the oleylamine species present on the Cs4PbBr6nanocrystals' surface and produces polysuccinamic acid, which, in turn, triggers the Cs4PbBr6to CsPbBr3conversion. The transformation occurs through the formation of Cs4PbBr6–CsPbBr3heterostructures as intermediates, which are captured because of the mild reactivity of PMAO and are investigated by high-resolution electron microscopy. The Cs4PbBr6–CsPbBr3heterostructures demonstrate a dual emission at cryogenic temperature with an indication of the energy transfer from Cs4PbBr6to CsPbBr3. The fully-transformed CsPbBr3NCs have high photoluminescence quantum yield and enhanced colloidal stability, which we attribute to the adhesion of polysuccinamic acid to the NC surface through its multiple functional groups in place of oleate and alkylammonium ligands. The PMAO-induced transformation of Cs4PbBr6NCs opens up a strategy for the chemical modification of metal halide NCs initially passivated with nucleophilic amines.

Two-dimensional (2D) layered perovskites recently emerged as one of the most promising materials for optoelectronics. These not only behave like a quantum well structures, but also on doping Mn(II) ions at the Pb site result as a highly emissive doped material. These structures can also be used as a starting material for obtaining 3D perovskites. Thermal treatment of Mn(II)-incorporated layered perovskites in presence of Cs(I) ions led to Mn(II)-doped 2D platelet–shaped perovskites, which also tune their dimensions with varying dopant ion concentrations. Keeping the importance of the 2D-layered perovskites, this review focused on the basic structures to the recently developed synthetic strategies and their optical properties of layered structured perovskites, Mn(II)-doped layered perovskites, and Mn(II)-doped 2D platelet–shaped perovskites.

The vast majority of lead halide perovskite (LHP) nanocrystals (NCs) are currently based on either a single halide composition (CsPbCl3, CsPbBr3, and CsPbI3) or an alloyed mixture of bromide with either Cl–or I–[i.e., CsPb(Br:Cl)3or CsPb(Br:I)3]. In this work, we present the synthesis as well as a detailed optical and structural study of two halide alloying cases that have not previously been reported for LHP NCs: Cs2PbI2Cl2NCs and triple halide CsPb(Cl:Br:I)3NCs. In the case of Cs2PbI2Cl2, we observe for the first time NCs with a fully inorganic Ruddlesden–Popper phase (RPP) crystal structure. Unlike the well-explored organic–inorganic RPP, here, the RPP formation is triggered by the size difference between the halide ions. These NCs exhibit a strong excitonic absorption, albeit with a weak photoluminescence quantum yield (PLQY). In the case of the triple halide CsPb(Cl:Br:I)3composition, the NCs comprise a CsPbBr2Cl perovskite crystal lattice with only a small amount of incorporated iodide, which segregates at RPP planes’ interfaces within the CsPb(Cl:Br:I)3NCs. Supported by density functional theory calculations and postsynthetic surface treatments to enhance the PLQY, we show that the combination of iodide segregation and defective RPP interfaces are most likely linked to the strong PL quenching observed in these nanostructures. In summary, this work demonstrates the limits of halide alloying in LHP NCs because a mixture that contains halide ions of very different sizes leads to the formation of defective RPP interfaces and a severe quenching of LHP NC’s optical properties.

Lead halide perovskites are considered to be most promising photovoltaic materials. Highest efficiency and improved stability of perovskite solar cells have been achieved by using cation and anion mixtures. Experimental information on electronic and ionic charge carriers is key to evaluate device performance, as well as processes of photo‐decomposition and photo‐demixing which are observed in these materials. Here, we measure ionic and electronic transport properties and investigate various cation and anion substitutions with a special eye on their photo‐ionic effect, following our previous study on CH3NH3PbI3, where we found that light enhances not only electronic but also ionic conductivities. We find that this phenomenon is very sensitive to the nature of the halide, while the cationic substitutions are less relevant. Based on the observation that the ionic conductivity enhancement found for iodide perovskites is significantly weakened by bromide substitution, we provide a chemical rationale for the photo‐demixing in mixed halide compositions., The photo‐effect on ion conduction in mixed cation and halide perovskites is studied. Unlike A‐site substitution, anion replacement is of great influence. In I‐Br mixtures the differences in hole localization and defect formation favor (reversible) photo‐demixing (the situation in the right part is simplified as the interstitial neutral iodine is further stabilized by ionic rearrangement, and the hole in the bromide is delocalized over several regular anions).

Lead halide perovskites of APbX_3 type [A = Cs, formamidinium (FA), methylammonium; X = Br, I] in the form of ligand-capped colloidal nanocrystals (NCs) are widely studied as versatile photonic sources. FAPbBr_3 and CsPbBr_3 NCs have become promising as spectrally narrow green primary emitters in backlighting of liquid-crystal displays (peak at 520–530 nm, full width at half-maximum of 22–30 nm). Herein, we report that wet ball milling of bulk APbBr_3 (A = Cs, FA) mixed with solvents and capping ligands yields green luminescent colloidal NCs with a high overall reaction yield and optoelectronic quality on par with that of NCs of the same composition obtained by hot-injection method. We emphasize the superiority of oleylammonium bromide as a capping ligand used for this procedure over the standard oleic acid and oleylamine. We also show a mechanically induced anion-exchange reaction for the formation of orange-emissive CsPb(Br/I)_3 NCs., ACS Applied Nano Materials, 1 (3), ISSN:2574-0970

Lead halide perovskites are currently receiving increasing attention due to their potential to combine easy active layers fabrication, tunable electronic and optical properties with promising performance of optoelectronic and photonic device prototypes. In this paper, we review the main development steps and the current state of the art of the research on lead halide perovskites amplified spontaneous emission and on optically pumped lasers exploiting them as active materials.

[EN] This paper explores the gas sensing properties of graphene nanolayers decorated with lead halide perovskite (CH3NH3PbBr3) nanocrystals to detect toxic gases such as ammonia (NH3) and nitrogen dioxide (NO2). A chemical-sensitive semiconductor film based on graphene has been achieved, being decorated with CH3NH3PbBr3 perovskite (MAPbBr3) nanocrystals (NCs) synthesized, and characterized by several techniques, such as field emission scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. Reversible responses were obtained towards NO2 and NH3 at room temperature, demonstrating an enhanced sensitivity when the graphene is decorated by MAPbBr3 NCs. Furthermore, the effect of ambient moisture was extensively studied, showing that the use of perovskite NCs in gas sensors can become a promising alternative to other gas sensitive materials, due to the protective character of graphene, resulting from its high hydrophobicity. Besides, a gas sensing mechanism is proposed to understand the effects of MAPbBr3 sensing properties, This work was funded in part by MINECO, MICINN and FEDER via grants no. RTI2018-101580-B-I00, by AGAUR under grant. 2017SGR 418 J.C.C gratefully acknowledges a doctoral fellowship from URV under the Marti i Franques fellowship program. E.L. is supported by the Catalan institution for Research and Advanced Studies via the 2012 and 2018 Editions of the ICREA Academia Award. P.A. acknowledges the financial support from the Spanish Government through 'Severo Ochoa"(SEV-2016-0683, MINECO) and PGC2018-099744-B-I00 (MCIU/AEI/FEDER, UE), and R.G.A. acknowledges FPI scholarship the Spanish Government-MINECO for a (TEC2015-74405-JIN), MAT2015-69669-P.

The synthesis of hydroxylammonium lead iodide NH3OHPbI3 was accomplished by means of the reaction between water solutions of HI and NH2OH with PbI2 in sulfolane in conjunction with either crystallization by CH2Cl2 vapor diffusion or sulfolane extraction with toluene. The appropriate choice of the solvent was found to be crucial in order to attain the desired material. The synthesized compound was extensively characterized by single crystal and powder X-ray diffraction, UV-Vis diffuse reflectance spectroscopy, FT-IR spectroscopy, 1H-NMR spectroscopy, TG-DTA-QMS EGA (Evolved Gas Analysis), ESI-MS, and CHNS analysis. NH3OHPbI3 is an extremely reactive, deliquescent solid that easily oxidizes in air releasing iodine. Furthermore, it is the first reported perovskite to melt (m.p. around 80 °C) before decomposing exothermally at 103 °C. Such a chemical behavior, together with its optical absorption properties (i.e. yellow-colored perovskite), renders this material totally unsuitable for photovoltaic applications. The deliquescence of the material is to be ascribed to the strong hydrophilicity of hydroxylammonium ion. On the other hand, the relatively high Bronsted acidity of hydroxylammonium (pKa = 5.97) compared to other ammonium cations, promotes the reduction of atmospheric oxygen to water and the NH3OHPbI3 oxidation. The crystal structure, determined by single crystal X-ray diffraction with synchrotron radiation, is orthorhombic, but differs from the prototypal perovskite structure. Indeed it comprises infinite chains of face-sharing PbI6 octahedra along the c-axis direction with hydroxylammonium cations positioned between the columns, forming layers on the ac plane. The solvent intercalates easily between the layers. The crystal structure is apparently anomalous considering that the expected Goldschmidt's tolerance factor for the system (0.909) lies in the range of a stable prototypal perovskite structure. Therefore, the strong hydrogen bond forming tendency of hydroxylamine is likely to account for the apparent structural anomaly.

Hybrid lead halide perovskite (PS) derivatives have emerged as very promising materials for the development of optoelectronic devices in the last few years. At the same time, inorganic nanocrystals with quantum confinement (QDs) possess unique properties that make them suitable materials for the development of photovoltaics, imaging and lighting applications, among others. In this work, we report on a new methodology for the deposition of high quality, large grain size and pinhole free PS films (CH3NH3PbI3) with embedded PbS and PbS/CdS core/shell Quantum Dots (QDs). The strong interaction between both semiconductors is revealed by the formation of an exciplex state, which is monitored by photoluminescence and electroluminescence experiments. The radiative exciplex relaxation is centered in the near infrared region (NIR), ≈1200 nm, which corresponds to lower energies than the corresponding band gap of both perovskite (PS) and QDs. Our approach allows the fabrication of multi-wavelength light emitting diodes (LEDs) based on a PS matrix with embedded QDs, which show considerably low turn-on potentials. The presence of the exciplex state of PS and QDs opens up a broad range of possibilities with important implications in both LEDs and solar cells. Generalitat Valenciana PROMETEOII/2014/020 PROMETEOII/2014/059 ISIC/2012/008 Spanish MINECO (Ministry of Economy and Competitiveness) MAT2013-47192-C3-1-R MAT2015-70611-ERC TEC2014-53727-C2-1-R Spanish MINECO

Organo-lead halide perovskites have recently attracted great interest for potential applications in thin-film photovoltaics and optoelectronics. Herein, we present a protocol for the fabrication of this material via the low-pressure vapor assisted solution process (LP-VASP) method, which yields ~19% power conversion efficiency in planar heterojunction perovskite solar cells. First, we report the synthesis of methylammonium iodide (CH(3)NH(3)I) and methylammonium bromide (CH(3)NH(3)Br) from methylamine and the corresponding halide acid (HI or HBr). Then, we describe the fabrication of pinhole-free, continuous methylammonium-lead halide perovskite (CH(3)NH(3)PbX(3) with X = I, Br, Cl and their mixture) films with the LP-VASP. This process is based on two steps: i) spin-coating of a homogenous layer of lead halide precursor onto a substrate, and ii) conversion of this layer to CH(3)NH(3)PbI(3-x)Br(x) by exposing the substrate to vapors of a mixture of CH(3)NH(3)I and CH(3)NH(3)Br at reduced pressure and 120 °C. Through slow diffusion of the methylammonium halide vapor into the lead halide precursor, we achieve slow and controlled growth of a continuous, pinhole-free perovskite film. The LP-VASP allows synthetic access to the full halide composition space in CH(3)NH(3)PbI(3-x)Br(x) with 0 ≤ x ≤ 3. Depending on the composition of the vapor phase, the bandgap can be tuned between 1.6 eV ≤ E(g )≤ 2.3 eV. In addition, by varying the composition of the halide precursor and of the vapor phase, we can also obtain CH(3)NH(3)PbI(3-x)Cl(x). Films obtained from the LP-VASP are reproducible, phase pure as confirmed by X-ray diffraction measurements, and show high photoluminescence quantum yield. The process does not require the use of a glovebox.

International audience; Revealing the crystal structure of lead halide perovskite nanocrystals is essential for the optimization of stability of these emerging materials in applications such as solar cells, photodetectors and light emitting devices. We use magneto-photoluminescence spectroscopy of individual perovskite CsPbBr3 nanocrystals as a unique tool to determine their crystal structure, which imprints distinct signatures in the excitonic sublevels of charge complexes at low temperatures. At zero magnetic field, the identification of two classes of photoluminescence spectra, displaying either two or three sublevels in their exciton fine structure, shows evidence for the existence of two crystalline structures, namely tetragonal D4h and orthorhombic D2h phases. Magnetic field shifts, splitting and coupling of the sublevels provide a determination of the diamagnetic coefficient and valuable information on the exciton g-factor and its anisotropic character. Moreover, this spectroscopic study reveals the optical properties of charged excitons and allows the extraction of the electron and hole g-factors for perovskite systems.

Several aspects on the photophysical characterization of lead halide hybrid organic inorganic perovskite solar cells remain unsolved. It has been observed that ionic transport and polarization of the interfaces cause very slow changes that interfere with transient measurements with effects that cannot be separated from recombination kinetics. Here we establish a protocol of initial measurement of the solar cell that provides information on recombination characteristics prior to applying any voltage cycling. The photovoltaic device is measured by several methods (photovoltage versus light intensity, open-circuit voltage decay, and impedance spectroscopy) while minimizing the exposure to external voltage stimulus to avoid ionic migration to the contacts. Results are independently confirmed by the analysis of samples with interdigitated electrodes. We show that the high-efficiency perovskite solar cells behave very closely to a bulk recombination ideal photovoltaic model. However, when voltage is scanned to determine current density voltage curves and impedance spectroscopy at fixed illumination intensity, the cell undergoes significant changes, which we attribute to a dominance of recombination at contacts that have been modified by ionic polarization. Our method provides an effective approach for determining quantitatively the rather significant changes that occur to perovskite solar cells during standard measurements, such as current voltage curves.

Organic–inorganic metal halide perovskites have recently demonstrated outstanding efficiencies in photovoltaics as well as highly promising performances for a wide range of optoelectronic applications such as lasing, light emission, optical detectors, and even for radiation detection. Key to the realization of functional perovskite micro/nanosystems on the ubiquitous silicon optoelectronics platform is through sophisticated lithography. Despite the rapid progress made in halide perovskite lasing, direct lithographic patterning of perovskite films to form optical cavities on conventional substrates remains extremely challenging. This study realizes room‐temperature high‐quality factor whispering‐gallery‐mode lasing (Q ≈ 1210) from patterned lead halide perovskite microplatelets fabricated in periodic arrays on silicon substrate with micropatterned BN film as the buffer layer. By varying the size of the platelets, modal selectivity for single mode lasing can be achieved with different cavity sizes or by simply breaking the structural symmetry of the cavity through designing the pattern. Importantly, this work demonstrates a straightforward, versatile bottom‐up scalable strategy to realize high‐quality periodic perovskite arrays with variable cavity sizes for large‐area light‐emitting and optical gain applications.

The use of a solution process to grow perovskite thin films allows to extend the material processability. It is known that the physicochemical properties of the perovskite material can be tuned by altering the solution precursors as well as by controlling the crystal growth of the film. This advancement necessarily implies the need for an understanding of the kinetic phenomena for the thin-film formation. Therefore, in this work we review the state of the art of perovskite hybrid crystal growth, starting from a comprehensive theoretical description towards broad experimental investigations. One part of the study focuses on rapid thermal annealing as a tool to control nucleation and crystal growth. We deduce that controlling crystal growth with high-precision photonic sintering simplifies the experimental framework required to understand perovskite crystallization. These types of synthesis methods open a new empirical parameter space. All this knowledge serves to improve the perovskite synthesis and the thin films' quality, which will result in higher device performances.

Highly photoluminescent hybrid lead halide perovskite nanoparticles have recently attracted wide interest in the context of high-stake applications, such as light emitting diodes (LEDs), light emitting transistors and lasers. In addition, they constitute ideal model systems to explore energy and charge transport phenomena occurring at the boundaries of nanocrystalline grains forming thin films in high-efficiency perovskite solar cells (PSCs). Here we report a complete photophysical study of CH3NH3PbBr3 perovskite nanoparticles suspended in chlorobenzene and highlight some important interaction properties. Colloidal suspensions under study were constituted of dispersed aggregates of quasi-2D platelets of a range of thicknesses, decorated with 3D-like spherical nanoparticles. These types of nanostructures possess different optical properties that afford a handle for probing them individually. The photophysics of the colloidal particles was studied by femtosecond pump-probe spectroscopy and time-correlated single-photon counting. We show here that a cascade of energy and exciton-mediated charge transfer occurs between nanostructures: upon photoexcitation, localized excitons within one nanostructure can either recombine on a ps timescale, yielding a short-lived emission, or form charge-transfer states (CTSs) across adjacent domains, resulting in longer-lived photoluminescence in the millisecond timescale. Furthermore, CTSs exhibit a clear signature in the form of a strong photoinduced electroabsorption evidenced in femtosecond transient absorption measurements. Charge transfer dynamics at the surface of the nanoparticles have been studied with various quenchers in solution. Efficient hole transfer to N,N,N′,N′-tetrakis(4-methoxyphenyl)benzidine (MeO-TPD) and 1,4-bis(diphenyl-amino)benzene (BDB) donors was attested by the quenching of the nanoparticles emission. The charge transfer rate was limited by the organic layer used to stabilize the nanoparticles, which acted as a wide spacer between reactants. The forward charge transfer was found to take place in the sub-microsecond time-scale in competition with slow carrier recombination, while back transfer was shown to occur with a time-constant τ = 25 ms., Chemical Science, 8 (6), ISSN:2041-6520, ISSN:2041-6539

Combining halide perovskites with tailored dimensionality into two/three-dimensional (2D/3D) systems has revealed a powerful strategy to boost the performances of perovskite photovoltaics (PVs). Despite recent advances, a clear understanding of the intimate link between interface structure and physics is still missing, leading so far to a blind optimization of the 2D/3D PVs. Here, we reveal the impact of 2D/3D crystal alignment in driving interface charge-recombination dynamics. The 2D crystal growth and orientation are manipulated by specific fluorination of phenethylammonium (PEA), used here as the organic cation backbone of the 2D component. By means of time-resolved optoelectronic analysis from the femto- to microsecond regions, we demonstrate a static function of the 2D layer as an electron barrier and homogeneous surface passivant, together with a dynamic role in retarding back charge recombination. Our results reveal a crucial dependence of such beneficial effects with the 2D layer, leading to an enhanced open-circuit voltage (Voc), mostly attributed to the 2D phase which orients parallel on the 3D layer. Such findings provide a deep understanding and delineate precise guidelines for the smart design of multidimensional perovskite interfaces for advanced PVs and beyond.