Perovskite Interface Research Articles

Strain-Induced Gradient Distribution of Dopants at a Perovskite Interface.

Interfaces often trap dopants for segregation and significantly affect the material properties. Because interfacial segregation sometimes is harmful, revealing mechanisms to reduce the extent of interface segregation is important. Here we investigate the Sr segregation behavior in LaTiO3.5/LaTiO3/LaTiO3.5 sandwich heterostructures by transmission electron microscopy and first-principles calculations. This reveals that Sr atoms prefer to segregate in LaTiO3 by replacing La atoms rather than LaTiO3.5. The Sr concentration in LaTiO3 increases with the thickness of the LaTiO3 layer and exhibits an obvious gradient distribution. First-principles calculations suggest that the electrostatic potential drives Sr atoms from LaTiO3.5 to LaTiO3. The low Sr concentration at the interfaces is induced by an interfacial strain. The sandwiched LaTiO3 layer changes from n-type conduction to insulation and to p-type conduction with an increase in Sr concentration. The finding that the strain concentration sometimes reduces the extent of interface segregation provides a new approach for the design and regulation of material interfaces.

Tailoring Buried Interface and Minimizing Energy Loss Enable Efficient Narrow and Wide Bandgap Inverted Perovskite Solar Cells by Aluminum Glycinate Based Organometallic Molecule.

Rational regulation of Me-4PACz/perovskite interface has emerged as a significant challenge in the pursuit of highly efficient and stable perovskite solar cells (PSCs). Herein, an organometallic molecule of aluminum glycinate (AG) that contained amine (-NH2) and aluminum hydroxyl (Al-OH) groups is developed to tailor the buried interface and minimize interface-driven energy losses. The Al-OH groups selectively bonded with unanchored O═P-OH and bare NiO-OH to optimize the surface morphology and energy levels, while the -NH2 group interacted specifically with Pb2+ to retard perovskite crystallization, passivate buried Pb-related defects, and release residual interface stress. These interactions facilitate the interface carrier extraction and reduce interface-driven energy losses, thereby realizing a balanced charge carrier transport. Consequently, AG-modified narrow bandgap (1.55 eV) PSC demonstrates an efficiency of 26.74% (certified 26.21%) with a fill factor of 86.65%; AG-modified wide bandgap (1.785 eV) PSC realizes 20.71% champion efficiency with excellent repeatability. These PSCs maintain 91.37%, 91.92%, and 92.00% of their initial efficiency after aging in air atmosphere, the nitrogen-filled atmosphere at 85°C, and continuously tracking at the maximum power-point under one-sun illumination (100 mW cm-2) for 1200 h, respectively.

Intermediate Layer‐Assisted Trap Density Reduction in Low‐Power Optoelectronic Memristors for Multifunctional Systems

AbstractThe rapid expansion of the Internet of Things demands low‐power devices that integrate memory, sensors, and logic functions. Perovskite materials show promise for low‐power optoelectronic memristors; however, challenges such as nonuniform trap distribution and uncontrolled filament formation hinder their resistive switching performance. To overcome these issues, a TiO2 nanofilm via atomic layer deposition as a base layer for filament formation, is introduced. This layer passivates interfacial defects by forming strong chemical interactions with Pb2+ and I− ions at the perovskite interface, significantly reducing trap densities (interface trap density decreases 15‐fold to 3.0 × 1016 cm−3, and bulk trap density to 1.8 × 1014 cm−3). Improved energy band alignment enables efficient electron transport, yielding a low‐V SET (+0.24 V) and excellent low‐power (≈0.7 µW) nonvolatile memory performance. Additionally, the device reliably detects near‐infrared illumination as an optical input and enables reconfigurable image recognition using a 5 × 5 array under combined stimuli. It also facilitates the implementation of complex logic gates, such as AND, OR, and flip‐flops. This paper demonstrates the potential for integrating nonvolatile memory, sensing, and logic functionalities into a single low‐power device through the incorporation of a TiO2 nanolayer.

Enlarging moment and regulating orientation of buried interfacial dipole for efficient inverted perovskite solar cells

Carrier transport and recombination at the buried interface of perovskite have seriously restricted the further development of inverted perovskite solar cells (PSCs). Herein, an interfacial dipolar chemical bridge strategy to address this issue is presented. 2-(Diphenylphosphino) acetic acid (2DPAA) is selected as the linker to reconstruct the interfacial dipole, which effectively enlarges the interfacial dipole moment to 5.10 D and optimizes to a positive dipole orientation, thereby accelerating vertical hole transport, suppressing nonradiative recombination and promoting the perovskite crystallization. The champion inverted device yields a high power conversion efficiency (PCE) of 26.53% (certified 26.02%). Moreover, this strategy is extended to the wide-bandgap perovskite and large-area devices, which delivers high PCEs of 22.02% and 24.11%, respectively. The optimized devices without encapsulation also demonstrate great long-term shelf and operational stability. Our work highlights the importance of interfacial dipole moment and orientation at the buried interface to realize efficient and stable inverted PSCs.

In situ Polymerization Induced Seed-Root Anchoring Structure for Enhancing Stability and Efficiency in Perovskite Solar Modules.

The escape of organic cations over time from defective perovskite interface leads to non-stoichiometric terminals, significantly affecting the stability of perovskite solar cells (PSCs). How to stabilize the interface composition under environmental stress remains a grand challenge. To address this issue, we utilize thiol-functionalized particles as a "seed" and conduct in situ polymerization of 2,2,3,4,4,4-hexafluorobutyl methacrylate (HFMA) as a "root" at the bottom of the perovskite layer. In this process, the thiol group acts as the initiation site for the polymerization of HFMA, while the fluorine groups in HFMA firmly anchor the organic cations of the perovskite through multiple hydrogen bonds. This strategy resembles how seeds take root in soil to prevent soil erosion. This bionic seed-rooting structure effectively stabilizes the stoichiometry of the perovskite, thus suppressing the escape of organic cations. As a result, the perovskite films with seed-rooting structures exhibit enhanced stability under harsh vacuum thermal conditions (150 °C, <10 Pa). The resulting PCS achieves an efficiency of 25.64 % and a 22.4 cm2 module efficiency of 22.61 %. After 1300 hours of 1-sun illumination at 85 % relative humidity and 65 °C (ISOS-L-3 protocol), the perovskite solar module maintains 90 % of its initial efficiency.

In‐situ Polymerization Induced Seed‐Root Anchoring Structure for Enhancing Stability and Efficiency in Perovskite Solar Modules

The escape of organic cations over time from defective perovskite interface leads to non‐stoichiometric terminals, significantly affecting the stability of perovskite solar cells (PSCs). How to stabilize the interface composition under environmental stress remains a grand challenge. To address this issue, we utilize thiol‐functionalized particles as a "seed" and conduct in situ polymerization of 2,2,3,4,4,4‐hexafluorobutyl methacrylate (HFMA) as a "root" at the bottom of the perovskite layer. In this process, the thiol group acts as the initiation site for the polymerization of HFMA, while the fluorine groups in HFMA firmly anchor the organic cations of the perovskite through multiple hydrogen bonds. This strategy resembles how seeds take root in soil to prevent soil erosion. This bionic seed‐rooting structure effectively stabilizes the stoichiometry of the perovskite, thus suppressing the escape of organic cations. As a result, the perovskite films with seed‐rooting structures exhibit enhanced stability under harsh vacuum thermal conditions (150 °C, &lt; 10 Pa). The resulting PCS achieves an efficiency of 25.64% and a 22.4 cm2 module efficiency of 22.61%. After 1300 hours of 1‐sun illumination at 85% relative humidity and 65 °C (ISOS‐L‐3 protocol), the perovskite solar module maintains 90% of its initial efficiency.

Solvent-dripping modulated 3D/2D heterostructures for high-performance perovskite solar cells

The controlled growth of two-dimensional (2D) perovskite atop three-dimensional (3D) perovskite films reduces interfacial recombination and impedes ion migration, thus improving the performance and stability of perovskite solar cells (PSCs). Unfortunately, the random orientation of the spontaneously formed 2D phase atop the pre-deposited 3D perovskite film can deteriorate charge extraction owing to energetic disorder, limiting the maximum attainable efficiency and long-term stability of the PSCs. Here, we introduce a meta-amidinopyridine ligand and the solvent post-dripping step to generate a highly ordered 2D perovskite phase on the surface of a 3D perovskite film. The reconstructed 2D/3D perovskite interface exhibits reduced energetic disorder and yields cells with improved performance compared with control 2D/3D samples. PSCs fabricated with the meta-amidinopyridine-induced phase-pure 2D perovskite passivation show a maximum power conversion efficiency of 26.05% (a certified value of 25.44%). Under damp heat and outdoor tests, the encapsulated PSCs maintain 82% and 75% of their initial PCE after 1000 h and 840 h, respectively, demonstrating improved practical durability.

High‐Purity Photoactive α‐Phase for Flexible Perovskite Photodetectors with Modified Electron Transport Layer

AbstractRegulating the crystallization process of organic–inorganic halide perovskite is essential for the fabrication of reproducible and efficient optoelectronic devices. Herein, a vacuum‐assisted heating treatment strategy for precursor is developed to obtain a high‐purity photoactive phase perovskite. By eliminating residual H2O molecules from raw materials and solvents, the method prevents the Pb–I framework of perovskite from being destroyed. Additionally, the pre‐treated precursor possesses high‐valence iodoplumbate species leading to preferable crystallization for perovskite films. Furthermore, a high on‐off ratio of 1103 is attained under 0 V and 550 nm illumination by employing a vertical n–i–p photodetector based on pure 𝛼‐phase perovskite films and interface passivation carried out by incorporating phenethylammonium hydroiodide (PEAI) in the n‐type electron transport layer. The photodetector exhibits high sensitivity with the peak responsivity of 0.93 A W−1 and the detectivity of 1.55 × 1012 Jones in the visible light range, making it a potential candidate for an imaging application. The flexible photodetector fabricated on polyethylene terephthalate (PET) substrate maintains 98.6% photocurrent density after 300 times of bending and preliminarily realizes imaging sensing. The heat‐treating strategy improves the adaptability of perovskite to complex environments and enables the preparation of reproducible pure 𝛼‐phase perovskite films, which boast enormous potential for optoelectronic applications.

Boosting Efficiency in Flexible Perovskite Solar Cells with Novel HTLs and ETLs: A drift‐diffusion numerical study of CBz‐PAI Interlayers and MXene Back Contacts

AbstractIn this study, the functioning of flexible perovskite solar cells (FPSCs) is examined using drift‐diffusion SCAPS‐1D simulations under ideal conditions. The focus is on the CBz‐PAI interlayer at the perovskite and hole transport layer (HTL) interface and the impact of innovative materials for HTLs, electrons transport layers (ETLs), and transparent conduction electrodes (TCOs), such as AZO and MXene, in the front and back contacts. Initially, 50 configurations of ETLs, including BaZrS3, SnS2, STO, WS2, and ZrS2, as well as HTLs such as ACZTSe, CuBiS3, CZGS, and D‐PBTTT‐14, are tested to identify optimal architecture for enhancing device efficiency. The incorporation of the CBz‐PAI interlayer effectively reduces interfacial charge recombination, minimizing VOC losses and boosting overall performance. After further optimization and the integration of MXene as a back contact, the final FPSC design (PET/ITO/AZO/ZrS2/(FAPbI3)0.77(MAPbBr3)0.14(CsPbI3)0.09/CBz‐PAI/CZGS/MXene‐V3C2F2) achieves an impressive PCE of 27.17%, setting a new benchmark for FPSC efficiency.

Few-Layered Black Phosphorene as Hole Transport Layer for Novel All-Inorganic Perovskite Solar Cells.

The CsPbBr3 perovskite exhibits strong environmental stability under light, humidity, temperature, and oxygen conditions. However, in all-inorganic perovskite solar cells (PSCs), interface defects between the carbon electrode and CsPbBr3 limit the carrier separation and transfer rates. We used black phosphorus (BP) nanosheets as the hole transport layer (HTL) to construct an all-inorganic carbon-based CsPbBr3 perovskite (FTO/c-TiO2/m-TiO2/CsPbBr3/BP/C) solar cell. BP can enhance hole extraction capabilities and reduce carrier recombination by adjusting the interface contact between the perovskite and the carbon layer. Due to the coordination of the energy structure related to interface charge extraction and transfer, BP, as a new type of hole transport layer for all-inorganic CsPbBr3 solar cells, achieves a power conversion efficiency (PCE) that is 1.43% higher than that of all-inorganic carbon-based CsPbBr3 perovskite solar cells without a hole transport layer, reaching 2.7% (Voc = 1.29 V, Jsc = 4.60 mA/cm2, FF = 48.58%). In contrast, the PCE of the all-inorganic carbon-based CsPbBr3 perovskite solar cells without a hole transport layer was only 1.27% (Voc = 1.22 V, Jsc = 2.65 mA/cm2, FF = 39.51%). The unencapsulated BP-based PSCs device maintained 69% of its initial efficiency after being placed in the air for 500 h. In contrast, the efficiency of the PSC without HTL significantly decreased to only 52% of its initial efficiency. This indicates that BP can effectively enhance the PCE and stability of PSCs, demonstrating its great potential as a hole transport material in all-inorganic perovskite solar cells. BP as the HTL for CsPbBr3 PSCs can passivate the perovskite interface, enhance the hole extraction capability, and improve the optoelectronic performance of the device. The subsequent doping and compounding of the BP hole transport layer can further enhance its photovoltaic conversion efficiency in PSCs.

Ultrahigh Selectivity H2S Gas Sensor Based CsPbBr3 Perovskites via Pb-S Bonding Interaction.

High selectivity and sensitivity sensing of H2S gas play a decisive role in the early detection of sulfide solid-state battery failure. Herein, we construct the CsPbBr3 perovskite-based sensor that exhibits outstanding gas-sensing performance to H2S at room temperature, including high selectivity, fast response/recovery speed (73.5/275.6 s), humidity insensitivity, and long-term stability (6 weeks without degradation). The excellent selectivity of CsPbBr3 for H2S results from the formation of lead-sulfur (Pb-S) bonds exclusive to other molecules and upshifted the Fermi level at the perovskite interface by density functional theory (DFT) calculations. The in-situ experiments reveal the interaction of Pb-S bonding and the transformation of H2S molecules on the perovskite surface. The simple synthesis method and unique sensing mechanism based on perovskite semiconductors help build the room-temperature metal halide perovskite (MHP)-based gas sensors with high selectivity and fast response/recovery speed for solid-state battery failure detection in the future.

Formation Dynamics of Thermally Stable 1D/3D Perovskite Interfaces for High-Performance Photovoltaics.

Direct understanding of the formation and crystallization of low-dimensional (LD) perovskites with varying dimensionalities employing the same bulky cations can offer insights into LD perovskites and their heterostructures with 3D perovskites. In this study, the secondary amine cation of N-methyl-1-(naphthalen-1-yl)methylammonium (M-NMA+) and the formation dynamics of its corresponding LD perovskite are investigated. The intermolecular π-π stacking of M-NMA+ and their connection with inorganic PbI6 octahedrons within the product structures control the formation of LD perovskite. In an N,N-dimethylformamide (DMF) precursor solution, both 1D and 2D products can be obtained. Interestingly, due to the strong interaction between M-NMA+ and the DMF solvent, compared to the 1D phase, the formation of 2D perovskites is uniquely dependent on heterogeneous nucleation. Nevertheless, post-treatment of 3D perovskite films with an isopropanol solution of M-NMAI leads to the exclusive formation of thermally stable 1D phases on the surface. The resulting 1D/3D heterostructure facilitates perovskite solar cells (PSCs) to not only achieve a record efficiency of 25.51% through 1D perovskite passivation but also significantly enhance the thermal stability of unencapsulated devices at 85°C. This study deepens the understanding of the formation dynamics of LD perovskites and offers an efficient strategy for fabricating stable and high-performance PSCs.

Ordered self-assembled monolayer improved the buried interface of wide bandgap perovskite for efficient and stable semi-transparent solar cells

Ordered self-assembled monolayer improved the buried interface of wide bandgap perovskite for efficient and stable semi-transparent solar cells

2D Ruddlesden-Popper perovskite interface engineering for efficient perovskite solar cells with exceptional stability

2D Ruddlesden-Popper perovskite interface engineering for efficient perovskite solar cells with exceptional stability

Enhancing the performance and stability of organometal halide perovskite by using a feasible and economical interface material

AbstractOrganometal halide perovskites (OHPs) are one of the viable options for solar absorber materials because their power conversion efficiencies are getting better and better over time. In the conventional n-i-p-based configuration, TiO2 has been widely used as an electron transport layer (ETL). However, a number of constraints, such as low electron mobility and a mismatched band alignment with perovskite, restrict future advances in solar performance and device environmental stability. As a result, SnO2 has garnered a lot of interest as a potential replacement due to the comparatively low manufacturing temperature, better electron mobility and appropriate energy alignment w.r.t perovskite. In this experimental work, the primary emphasis was placed on enhancing the efficiency as well as the stability of OHPs by performing interface engineering at the ETL (SnO2)/perovskite interface. We improved the surface quality of the SnO2 ETL layer by using a material called 8-Hydroxyquinoline, which was quite inexpensive, and we prepared a favourable plane for the deposition of perovskite. Remarkably, the proposed surface modification material made the SnO2 layer easier to wet and impacted the growth of perovskite grains. This made the perovskite layer more compact and smooth. Our experimental findings imply that the OHPs’ enhanced charge recombination resistance and decreased charge transfer resistance are caused by effective defect passivation at the junction of the SnO2 and perovskite films, as well as a decrease in recombination due to unwanted trap states. The fabricated cell produced a power conversion efficiency (PCE) of 20.42%, higher than a PCE of 17.9% obtained for a device without surface modification. The proposed material for changing the surface also made OHPs more stable by reducing the surface paths for the reaction with humidity and reducing the amount of extra PbI2 in the perovskite layer. Various research groups have investigated the modification of SnO2 ETL using interfacial engineering methods and have contributed to enhancing OHPs’ solar performance and device stability.

Ligand-Mediated Surface Reaction for Achieving Pure 2D Phase Passivation in High-Efficiency Perovskite Solar Cells.

The surface passivation with the heterostructure of the 2D/3D stack has been widely used for boosting the efficiency of n-i-p perovskite solar cells (PSCs). However, the disordered quantum well width distribution of 2D perovskites leads to energy landscape inhomogeneity and crystalline instability, which limits the further development of n-i-p PSCs. Here, a versatile approach, ligand-mediated surface passivation, was developed to produce a phase-pure 2D perovskite passivation layer with a homogeneous energy landscape by dual-ligand codeposition. The preferential adsorption of 3,6-dimethyl-carbazole-9-ethylammonium iodide with a large molecular size and lower adsorption energy could regulate the surface reaction between the m-fluorophenylethylammonium iodide and perovskite surface, resulting in a 2D perovskite with a narrow quantum well distribution and a uniform surface potential distribution. Beyond this, the preservation of the surface-confined 2D passivation layer retained a higher electric field at the interface of perovskite and the hole transport layer. As a result, the champion device reached an efficiency of 25.86% for the 0.05 cm2 device and 25.08% for the 1 cm2 device, with enhanced operational stability (T90 > 1000 h) and much better thermal stability. Our work provides deeper insights into efficient and stable 2D passivation for PSCs.

Enhanced Efficiency and Stability of Triple-Cation Perovskite Solar Cells through Engineering of the Cell Interface with Phenylethylammonium Thiocyanate.

It is reported that the tricationic mixed halide perovskite Csx(FAyMA1-y)1-xPb(IzBr1-z)3 (CsFAMA) possesses a stable crystal structure and outstanding bandgap tunability, rendering it one of the most competitive candidates for commercial perovskite solar cells (PSCs). Nevertheless, the numerous defects at the interface of the tricationic perovskite give rise to a significant constraint on the light capture performance of the device. Simultaneously, water molecules form intermediate compounds with the perovskite at the interface via hydrogen bonds, accelerating the degradation of the perovskite. This study reports the introduction of two-dimensional (2D) phenylethylthiocyanate (PEASCN) at the interface of three-dimensional (3D) perovskite. This approach significantly passivates the surface defects of the perovskite. Concurrently, due to the propensity of the organic ammonium cation PEA+ to interact with the FA+ base within the perovskite, SCN- is exposed outward to form a small-molecule hydrophobic layer. This method markedly reduces the loss of charge recombination and significantly enhances the device stability. The results indicate that the efficiency of the conventional device treated solely with PEASCN is as high as 23.94%. The unsealed device retains 85.12% of its initial efficiency after being placed in a conventional environment for 500 h. Furthermore, this surface passivation and hydrophobic strategy can be universally applicable to perovskite types with a high FA+ content.

Methylthio Substituent in SAM Constructing Regulatory Bridge with Photovoltaic Perovskites

AbstractInverted (p‐i‐n) perovskite solar cells (PSCs) have experienced remarkable advancements in recent years, which is largely attributed to the development of novel hole‐transport layer (HTL) self‐assembled monolayer (SAM) materials. Methoxy (MeO−) groups are typically introduced into SAM materials to enhance their wettability and effectively passivate the perovskite buried interface. However, MeO‐based SAM materials exhibit a mismatch in highest occupied molecular orbital (HOMO) levels with perovskite layer due to the strong electron‐donating capability of methoxy group. In this work, we introduced a methylthio (MeS−) substituent that is superior to methoxy as a highly versatile self‐assembled molecular design strategy. As a soft base, sulfur atom forms a stronger Pb−S bond than oxygen. Additionally, within the CbzPh series of SAM materials, MeS−CbzPh demonstrates a more optimal HOMO level and enhanced hole transport properties. Consequently, the MeS−CbzPh HTL based device achieved an impressive power conversion efficiency (PCE) of 26.01 % and demonstrated high stability, retaining 93.3 % efficiency after 1000 hours of maximum power point tracking (MPPT). Moreover, in comparison with the commonly used 4PACz‐based SAM molecular series, MeS‐4PACz also exhibited the best performance among its peers. Our work provides valuable insights for the molecular design of SAM materials, offering a highly versatile functional substituent group.

Methylthio Substituent in SAM Constructing Regulatory Bridge with Photovoltaic Perovskites.

Inverted (p-i-n) perovskite solar cells (PSCs) have experienced remarkable advancements in recent years, which is largely attributed to the development of novel hole-transport layer (HTL) self-assembled monolayer (SAM) materials. Methoxy (MeO-) groups are typically introduced into SAM materials to enhance their wettability and effectively passivate the perovskite buried interface. However, MeO-based SAM materials exhibit a mismatch in highest occupied molecular orbital (HOMO) levels with perovskite layer due to the strong electron-donating capability of methoxy group. In this work, we introduced a methylthio (MeS-) substituent that is superior to methoxy as a highly versatile self-assembled molecular design strategy. As a soft base, sulfur atom forms a stronger Pb-S bond than oxygen. Additionally, within the CbzPh series of SAM materials, MeS-CbzPh demonstrates a more optimal HOMO level and enhanced hole transport properties. Consequently, the MeS-CbzPh HTL based device achieved an impressive power conversion efficiency (PCE) of 26.01 % and demonstrated high stability, retaining 93.3 % efficiency after 1000 hours of maximum power point tracking (MPPT). Moreover, in comparison with the commonly used 4PACz-based SAM molecular series, MeS-4PACz also exhibited the best performance among its peers. Our work provides valuable insights for the molecular design of SAM materials, offering a highly versatile functional substituent group.

Impact of Photogenerated Charge Carriers on the Stability of the 2D/3D Perovskite Interface

Impact of Photogenerated Charge Carriers on the Stability of the 2D/3D Perovskite Interface