Phenylethylammonium Research Articles

Ligand Coverage and Exciton Delocalization Control Chiral Imprinting in Perovskite Nanoplatelets

Chiral perovskites have recently generated significant interest, yet little is known about how their chiro-optical properties arise. In this study, chiral methylammonium lead halide perovskite nanoplatelets (NPLs) with varied halide and ligand compositions are prepared by using direct synthetic methods. Circular dichroism (CD) and 1H NMR studies find a nonlinear relationship between the chiroptical properties and the ratio of chiral phenylethylammonium (PEA) to achiral octylamine (OA) ligands on the NPL surface. We use density functional theory (DFT) computations and a chiral imprinted particle-in-a-box model to rationalize the experimentally observed CD spectra, and we find that the saturation of the induced chirality depends on the size of the perovskite exciton relative to the size of the ligand moleclues. Temperature-dependent CD and 1H NMR studies, combined with DFT analysis, show that both the CD intensity and sign depend strongly on the structure and orientation of the ligands. This work reveals the complex nature of chiral imprinting in perovskite nanostructures and establishes a simple physical model for ligand-induced chiral imprinting to guide the further development of chiral materials.

Theoretical investigation of octahedral tilting and bandgap non‐linearity in monolayer Ruddlesden‐Popper A 2 Pb 1‐x Ge x I 4 perovskites

2D Ruddlesden-Popper (RP) perovskites (R-NH3)2An−1BnX3n+1 with tailorable photovoltaic features of low toxicity, reduced dimensionality, and defect tolerance hold promise to overcome the main constraints of perovskite solar cells (PSCs). A systematic investigation of the structural and electronic properties of pure and mixed (R-NH3)2Pb1−xGexI4 systems was performed with and without spin-orbit coupling (SOC), by using density functional theory (DFT). The organic spacer cations (R-NH3+)2 of methylammonium (MA-CH3NH3+) and Phenylethyl ammonium (PEA-C6H5[CH2]2NH3+) with x = 0.0, 0.25, 0.50, 0.75, 1.0, resulted in the compositionally modified 32-permutations by systematically substituting the inorganic cations. Short-range ordering has categorized all studied compositions of (R-NH3)2Pb0.50Ge0.50I4 into column and battenberg schemes depending on the Ge defect site. The competing effects of octahedral tilting and lattice distortion with bandgap bowing and SOC, across Pb-Ge compositional systems, provide a systematic strategy to tune bandgaps. By controlling the cations' composition, these mixed 2D-perovskites outlined the strategy to achieve the desired bandgap and band positions. A rational design approach of low dimensional perovskites was adopted to tune the electronic properties through the spacer and inorganic cation engineering. Our findings expose the scope of monolayer-based systems as an ideal choice of absorber for the bottom sub-cell in all-perovskites 2D-3D tandem solar cell, harvesting light from visible (2.4 eV) up to infrared (1.2 eV) in the solar spectrum with features of defect tolerance, quantum and dielectric confinement, low bandgap, low effective masses, and high mobility.

Stable Yellow Light-Emitting Diodes Based on Quasi-Two-Dimensional Perovskites.

Perovskite light-emitting diodes (PeLEDs) show great potential in display and lighting because of their tunable wavelength, narrow emission bandwidths, and high color purity. Currently, the external quantum efficiency (EQE) of red and green PeLEDs has reached >23%. However, yellow PeLEDs are still rarely reported because of phase separation in mixed-halide perovskites and the coexistence of multiple phases in quasi-two-dimensional (quasi-2D) perovskites L2An-1BnX3n+1 (n = 1, 2, 3, ...), where L is a bulky organoammonium ligand. Here, we fabricate stable yellow PeLEDs by manipulating the phase distribution and incorporating rubidium cations (Rb+) in quasi-2D perovskites. The transient absorption results confirm that alkylammonium ligand butyl ammonium (BA) has a narrower phase distribution than phenylethyl ammonium (PEA) in the quasi-2D perovskites, resulting in a more blue-shifted emission peak. We further incorporate a proper molar ratio of Rb+ in the (BA)2CsPb2I7 perovskite to blue-shift the emission peak to the yellow range. Finally, the yellow PeLEDs exhibit an EQE of 3.5%, and the stable emission peak is located at 595 nm. Our work provides a useful approach for the fabrication of highly efficient and stable yellow PeLEDs.

Deep‐Blue Light‐Emitting Diodes Constructed with Perovskite Quasi‐2D and Nanocrystal Mixtures

AbstractIn the past several years, metal‐halide perovskites have attracted much attention for their promising applications in light‐emitting diodes (LEDs). Significant progress has been made in the development of high‐efficiency green, red, and near‐infrared perovskite LEDs (PeLEDs), but blue PeLEDs are still lagging behind. Although the external quantum efficiency (EQE) of blue PeLEDs has exceeded 10%, these works mainly focus on pure blue and sky‐blue regions. Creating deep‐blue electroluminescence (EL) with high stability, efficiency, and color purity is still a great challenge for PeLEDs. Herein, deep‐blue PeLEDs are reported which have been constructed with a mixture of a quasi‐2D phase and a nanocrystal phase by introducing a small diamine cation, ethylene diammonium (EDA2+), and the effect of EDA2+ on quasi‐2D perovskite crystallization is investigated. EDA2+ with two amino ending groups has a stronger inhibitory effect on high‐n phase growth than phenylethyl ammonium, leading to the formation of small nanocrystals. Further introduction of Na+ reduces the size of the nanocrystals and broadens the band gap. Based on these improvements, deep‐blue PeLEDs with EL peaks at 467 (EQE ≈ 1.7%) and 461 nm (EQE ≈ 1.1%) are successfully constructed. Thus, this study provides a useful strategy for improving the performance of deep‐blue PeLEDs.

Molecular Doping Enabling Mobility Boosting of 2D Sn2+‐Based Perovskites

Abstract2D metal halide perovskites are attracting great interest for their diverse applications owing to their intrinsic superior stability compared to their 3D counterparts; however, their device performance is limited by insufficient charge transport because of the insulating bulky organic ligands. Electrical doping is a direct and efficient method for improving the electrical properties of emerging semiconductors; however, its feasibility and mechanism remain elusive in metal halide perovskites. To clarify this issue, in this study, diverse organic/inorganic molecules are deposited on a typical phenylethyl ammonium tin iodide ((PEA)2SnI4) perovskite by constructing a heterojunction. In addition, the variations in the electrical performance of the perovskite semiconductor are monitored. The low work function of the dopant molecules enables the spontaneous electron transfer from the perovskite, resulting in the p‐doping effect on the perovskite host, which is verified by a series of characterization methods. The efficient charge transfer without deterioration of the perovskite microstructure improves the Hall mobility up to 100 cm2 V−1 s−1. Therefore, this work demonstrates the high doping efficiency of halide perovskites using a simple molecular charge transfer approach and provides a new opportunity for employing 2D perovskites in high‐efficiency optoelectronic devices.

Imaging and quantifying non-radiative losses at 23% efficient inverted perovskite solar cells interfaces

Interface engineering through passivating agents, in the form of organic molecules, is a powerful strategy to enhance the performance of perovskite solar cells. Despite its pivotal function in the development of a rational device optimization, the actual role played by the incorporation of interfacial modifications and the interface physics therein remains poorly understood. Here, we investigate the interface and device physics, quantifying charge recombination and charge losses in state-of-the-art inverted solar cells with power conversion efficiency beyond 23% - among the highest reported so far - by using multidimensional photoluminescence imaging. By doing that we extract physical parameters such as quasi-Fermi level splitting (QFLS) and Urbach energy enabling us to assess that the main passivation mechanism affects the perovskite/PCBM ([6,6]-phenyl-C61-butyric acid methyl ester) interface rather than surface defects. In this work, by linking optical, electrical measurements and modelling we highlight the benefits of organic passivation, made in this case by phenylethylammonium (PEAI) based cations, in maximising all the photovoltaic figures of merit.

Facilitate hole transport with thin 2D perovskite capping layer to passivate interface defects of 3D perovskite solar cells using PEABr

Hybrid 2D/3D-perovskites are attracting more interest in the area of organometal halide perovskite solar cells (PSCs) because of their high efficiency and extended environmental stability. The 3D portion in 2D/3D perovskites, serves as an active material with exceptional optoelectronic characteristics (for example excellent light absorption and an extended carrier lifetime), while its 2D counterpart protects against environmental conditions (water and oxygen) and increase the stability of the whole structure. In this study, a hetero-structure 2D/3D is constructed via spin-coating a phenyl-ethyl ammonium bromide (PEABr) solution upon over of (FA0.6MA0.4)PbI3 3D perovskite films. As compared to their 3D analogs, the PSC devices based on optimized 2D/3D hetero-structures display substantial improvements in photovoltaic efficiency due to the passivation of cationic and halide vacancies on the surface of 3D perovskite for better energy level alignments, longer carrier lifetimes, and fewer defects, which facilitate hole transfer and transport to the hole transport layer and reduce interface recombination centers. The extremely-thin film of 2D perovskite on the top of 3D perovskite boots the stability and reduces the crystal imperfection of 3D perovskite. Furthermore, the PEABr-treated perovskite device has a PCE of 20.57% as compared with the control device, which has a PCE of 17.01%.

Interface Engineering in Perovskite Solar Cells by Low Concentration of Phenylethyl Ammonium Iodide Solution in the Antisolvent Step

In spite of the outstanding properties of metal halide perovskites, its polycrystalline nature induces a wide range of structural defects that results in charge losses that affect the final device performance and stability. Herein, a surface treatment is used to passivate interfacial vacancies and improve moisture tolerance. A functional organic molecule, phenylethyl ammonium iodide (PEAI) salt, is dissolved with the antisolvent step. The additive used at low concentration does not induce formation of low‐dimensional perovskites species. Instead, the organic halide species passivate the surface of the perovskite and grain boundaries, which results in an effective passivation. For sake of generality, this facile solution‐processed synthesis was studied for halide perovskite with different compositions, the standard perovskite MAPbI3, and double cation perovskites, MA0.9Cs0.1PbI3 and MA0.5FA0.5PbI3, increasing the average photoconversion efficiency compared to the reference cell by 18%, 32%, and 4% respectively, observed for regular, n‐i‐p, and inverted, p‐i‐n, solar cell configurations. This analysis highlights the generality of this approach for halide perovskite materials in order to reduce nonradiative recombination as observed by impedance spectroscopy.

Molecular design of two-dimensional perovskite cations for efficient energy cascade in perovskite light-emitting diodes

Despite extensive reports on highly efficient perovskite light-emitting diodes, rules governing the design of suitable two-dimensional (2D) perovskite templating cation to facilitate formation of optimal emitter landscape for energy cascade remain largely elusive. With factors such as structure, size, functionalization, and charge capable of influencing the distribution of multidimensional perovskite phases, the importance of 2D templating cation design in determining film optoelectronic properties is indisputable. However, typical mono-functionalized 2D templating cations often result in larger lead halide octahedral spacing, which impedes effective charge transport. This has fueled investigation into the use of multiple cations for optimal domain distribution and improved charge transfer kinetics to the emitting species. In this study, we attempt to impart enhanced charge transfer characteristics to the resultant multidimensional perovskite by employing two bi-functionalized aromatic cations, namely, pyridinium ethyl ammonium and imidazolium ethyl ammonium, reminiscent of mono-functionalized phenyl ethyl ammonium, a widely used 2D perovskite templating cation. Although it is proposed that greater intermolecular bonding would enhance charge transfer rates, the simultaneous increase in lead halide octahedral distortion results in quenching of their corresponding 2D and multidimensional perovskite luminescence properties, correlated with increased defect density within the material. This manifests in the form of shorter PL decay lifetimes, lower PLQY, and device performance arising from inferior energy funneling. This study highlights the importance of designing 2D perovskite templating cations offering better transport and reduced octahedral distortion for the development of energy cascade-efficient, multidimensional perovskites.

Investigation of Interplay between Polyvinylpyrrolidone Interlayer and Perovskite Composition Affecting the Performance of Perovskite Light Emitting Diode

AbstractDevice structure and perovskite composition are two of the most important factors for maximizing the efficiency of light emitting diodes with perovskite as the light emitting layer. However, combining the best structures reported does not necessarily lead to better device performance. In the present study, the authors examine the device performance affected by the interplay between polyvinylpyrrolidone (PVP) as the interlayer and cesium (Cs)‐ or formamidinium (FA)‐based perovskite composition (PEA2(Cs0.87MA0.13)4Pb5Br16 (PEA: phenyl ethyl ammonium cation, MA: methyl ammonium cation) or PEA2FA2Pb3Br10, respectively). In the case of Cs‐based perovskite light‐emitting diodes (PeLEDs), PVP improves the formation of perovskite by preventing intermixing at the interface, thereby improving the device efficiency. On the other hand, although PVP is thought to behave similarly on FA‐based perovskite, it degrades device efficiency by decreasing hole injection and shifting the charge balance due to its insulating property. Based on the analysis, high efficiency Cs‐ and FA‐based PeLEDs of 12.31 and 24.5 cd A−1, respectively, are obtained.

In Situ‐Prepared Attachable Transparent Luminescent Solar Concentrators for Photovoltaic with Polymer Antireflection/Barrier Layer

As large‐area photon collection devices designed to convert sunlight into electricity, luminescent solar concentrators (LSCs) have been proposed for more than 40 years. In practical sunlight‐harvesting applications, existing glass windows or curtain walls have to be torn down and then replaced by traditional LSCs with planar optical waveguides, leading to high manufacture and installation costs. One alternative and attractive approach is to design and manufacture LSCs that are compatible with and can be attached directly onto the original building glass windows, which substantially reduces the overall costs. Herein, a feasible strategy of attachable transparent LSCs is proposed, converting ordinary glass to LSCs by simply attaching novel luminescent films. By integrating a phenylethylammonium (PEA)‐assisted perovskite−PVDF composite film with a polymer antireflection/barrier layer, as‐prepared composite films show dramatical improvement in photoluminescence quantum yield from 4.1% to 45.8% (11‐fold enhancement), substantially increased optical transmittance from 30.9% to 71.1% (at 700 nm), as well as strongly suppressed photoluminescence (PL) quenching during the attaching process. The fabricated attachable LSCs demonstrate a maximum optical efficiency of 2.8% at the geometric factor of 5 and retain 87% of initial optical efficiency after 2 months of storage in ambient conditions.

Benzodithiophene-Based Spacers for Layered and Quasi-Layered Lead Halide Perovskite Solar Cells.

Incorporating extended pi‐conjugated organic cations in layered lead halide perovskites is a recent trend promising to merge the fields of organic semiconductors and lead halide perovskites. Herein, we integrate benzodithiophene (BDT) into Ruddlesden–Popper (RP) layered and quasi‐layered lead iodide thin films (with methylammonium, MA) of the form (BDT)2MAn−1PbnI3n+1. The importance of tuning the ligand chemical structure is shown as an alkyl chain length of at least six carbon atoms is required to form a photoactive RP (n=1) phase. With N=20 or 100, as prepared in the precursor solution following the formula (BDT)2MAN−1PbNI3N+1, the performance and stability of devices surpassed those with phenylethylammonium (PEA). For N=100, the BDT cation gave a power conversion efficiency of up to 14.7 % vs. 13.7 % with PEA. Transient photocurrent, UV photoelectron spectroscopy, and Fourier transform infrared spectroscopy point to improved charge transport in the device active layer and additional electronic states close to the valence band, suggesting the formation of a Lewis adduct between the BDT and surface iodide vacancies.

(Invited) Lead-Free Halide Perovskites for Hydrogen Evolution

Metal halide perovskites (MHPs) semiconductors possess unique optical properties, such as high optical absorption in the visible region, tunable band-gap and long carrier lifetime, which have been extensively exploited in photovoltaics and optoelectronic applications.[1] More recently there has been a growing interests towards novel applications of MHPs, in particular in the field of solar-driven photocatalysis.[2] However, some of the most interesting photocatalytic reactions such as H2O splitting, CO2 and N2 reduction, dye degradation, require the use of water or alternative polar solvents, this represent a conundrum foreseeing MHPs utilization. In this talk we report clear evidence of water stability for two lead-free metal halide perovskites, namely dimethylammonium (DMA) DMASnBr3 and phenylethylammonium (PEA) PEA2SnBr4 obtained by means of diffraction, optical and x-ray photoelectron spectroscopy. The water stability for the 2D material is somehow expected due to the water-repulsive nature of the symmetry breaking organic cation, some computational work is addressing such improved water stability, showing also that the same mechanism is thought to protect tin from +2 to +4 oxidation. The stability in water of the 3D analogous represent instead an important innovation of the field. Such unprecedented water-stability has been applied to promote photocatalysis in aqueous medium, in particular by devising a novel composite material by coupling DMASnBr3 to g-C3N4, taking advantage from the combination of their optimal photophysical properties. The prepared composites provide an impressive hydrogen evolution rate >1700 μmol g-1 h-1 generated by the synergistic activity of the two composite constituents. DFT calculations provide insight into this enhancement deriving it from the favorable alignment of interfacial energy levels of DMASnBr3 and g-C3N4. The demonstration of an efficient photocatalytic activity for lead-free metal halide perovskites in water paves the way to a new class of light-driven catalysts working in aqueous environments.

Improving Photovoltaic Performance of Pb‐Less Halide Perovskite Solar Cells by Incorporating Bulky Phenylethylammonium Cations

Alloyed tin–lead (Sn–Pb) perovskite solar cells (PSCs) exhibit a broader photoresponse up to 1050 nm; however, their efficiency is inferior to that of Pb analogs. Trap‐assisted recombination associated with Sn vacancies formed through Sn2+ oxidation is a major detrimental factor, limiting their efficiency. By incorporating bulkier phenylethylammonium (PEA) cations into Sn–Pb alloyed perovskites, the nonradiative recombination by lowering the number of defects associated with Sn vacancies is reduced. Herein, the effects of PEA cations in different Sn–Pb halide perovskite compositions with a series of characterizations, such as photoluminescence, X‐ray photoelectron spectroscopy, and surface potential measurements, are investigated. As a result of the reduction of traps in PEA‐containing perovskites, a significant improvement of 40% and 15% in photovoltaic performance is observed for Sn‐rich and Pb‐rich Sn–Pb halide perovskites, respectively.

Phenyl Ethylammonium Iodide introduction into inverted triple cation perovskite solar cells for improved VOC and stability

Abstract The efficiency of more than 25% in organic-inorganic hybrid perovskite solar cells has made them very attractive in the pursuit of cheaper alternatives to Si-based devices. However, the stability of the perovskite solar cells was challenging, given their high susceptibility to moisture. Very few reports have emerged in this regard that investigated the influence of introducing large cations into a triple cation perovskite (TC-PVS), with several studies limited to single and dual cation perovskites. Further, the crystallization of TC-PVS on a polymer surface such as PEDOT is not straightforward, and their inclusion in inverted solar cell devices was limited. In this work, we investigated the impact of incorporating Phenyl ethyl ammonium cation into FAMACs triple cation composition. We demonstrated improvements in the crystallinity and more uniform coverage with little to no pinholes and smooth morphology for an optimum PEA amount of 1.67% in the precursor solution. The superior morphology, along with a passivation effect from a quasi 2D phase, led to increased photoluminescence and minority carrier lifetimes. Corresponding inverted photovoltaic devices prepared with PEA showed increased open-circuit voltage from 0.89 V for a control sample to 0.95 V for 1.67% PEA and 0.98 V for 5% PEA, doped devices in an inverted configuration. The efficiency, as a result, increased from 11.27% for a control device to 14.85% for a 1.67% PEA doped device. Further, PEA doped devices showed improved operational and thermal stability attributed to the higher moisture tolerance and light-soaking ability of the PEA doped TC-PVS compared to the undoped TC-PVS.

Two‐Step Thermal Annealing: An Effective Route for 15 % Efficient Quasi‐2D Perovskite Solar Cells

Low-dimensional perovskites (LDP) are nowadays recognized as promising materials for the realization of highly performing photovoltaic cells. However, issues related to film morphology, composition, crystal quality and material homogeneity limit the device performances and reproducibility. In this work, we implement a robust method for the deposition of a LDP mixing methylammonium (MA) and phenylethylammonium (PEA) cations to create the mixed system (PEA)2 MA39 Pb40 I121 by using a two-step thermal annealing treatment (at 60 and 100 °C). Our approach results in LDP films with high crystal quality and enhanced carrier lifetime, which double the power conversion efficiency of reference devices, reaching up to 15 %.

Highly efficient photoluminescence of 2D perovskites enabled by dimensional increasing

Herein, we proposed a dimension-increasing regulation strategy to realize the dimensionality engineering of perovskite from two-dimensional (2D) nanoplates (NPs) to quasi-two-dimensional (Q-2D) nanocrystals (NCs), and successfully prepared 2D (PEA)2PbBr4 NPs (PEA (phenylethylammonium) = C8H9NH3), Q-2D (PEA)2CsPb2Br7 (1) and (PEA)2Cs2Pb3Br10 (2) NCs. The photoluminescence dynamics changes from 2D (PEA)2PbBr4 NPs to Q-2D (1), (2) NCs by performing the time-resolved nanosecond transient absorption (NTAS) measurement for our perovskites. Compared with 2D (PEA)2PbBr4 NPs, we discovered for the first time that the electronic spectral redshift is intrinsic property of Q-2D NCs, which is caused by excitons transition to higher dimensionality. And the photoluminescence quantum yields (PLQYs) of Q-2D (1), (2) NCs is effectively increased from 8.780% to 14.72%, 21.80%, respectively. This directly verifies that Q-2D (1) and (2) NCs have enhanced their interlayer energy transfer capabilities. Moreover, the photoluminescence mechanism of these perovskites is investigated by the NTAS and the time-resolved photoluminescence (TR-PL) spectroscopy. The photophysical process of Q-2D samples exhibits a highly efficient and single photoluminescence pathway. The photoluminescence comes from the radiation recombination of free excitons. The Q-2D samples also have excellent photostability and decay lifetime stability. Our findings advance the research of improving 2D perovskites photoluminescence, and highlight potential of Q-2D NCs for optoelectronic applications.

Stabilizing γ-CsPbI3 Perovskite via Phenylethylammonium for Efficient Solar Cells with Open-Circuit Voltage over 1.3V.

Cesium lead iodide (CsPbI3 ) perovskite has gained great attention due to its potential thermal stability and appropriate bandgap (≈1.73eV) for tandem cells. However, the moisture-induced thermodynamically unstable phase and large open-circuit voltage (VOC ) deficit and also the low efficiency seriously limit its further development. Herein, long chain phenylethylammonium (PEA) is utilized into CsPbI3 perovskite to stabilize the orthorhombic black perovskite phase (γ-CsPbI3 ) under ambient condition. Furthermore, the moderate lead acetate (Pb(OAc)2 ) is controlled to combine with phenylethylammonium iodide to form the 2D perovskite, which can dramatically suppress the charge recombination in CsPbI3 . Unprecedentedly, the resulted CsPbI3 solar cells achieve a 17% power conversion efficiency with a record VOC of 1.33V, the VOC deficit is only 0.38V, which is close to those in organic-inorganic perovskite solar cells (PSCs). Meanwhile, the PEA modified device maintains 94% of its initial efficiency after exceeding 2000 h of storage in the low-humidity controlled environment without encapsulation.

Disentangling Second Harmonic Generation from Multiphoton Photoluminescence in Halide Perovskites using Multidimensional Harmonic Generation

Layered two-dimensional Ruddlesden-Popper (RP) halide perovskites are an intriguing class of semiconductors being explored for their linear and nonlinear optical and ferroelectric properties. Second harmonic generation (SHG) is commonly used to screen for noncentrosymmetric and ferroelectric materials. However, SHG measurements of perovskites can be obscured by their intense multiphoton photoluminescence (mPL). Here, we apply multidimensional harmonic generation as a method to eliminate the complications from mPL. By scanning and correlating both excitation and emission frequencies, we unambiguously assess whether a material supports SHG by examining if an emission feature scales as twice the excitation frequency. Measurements of a series of n = 2, 3 RP perovskites reveal that, contrary to previous belief, n-butylammonium (BA) RP perovskites are not SHG-active and thus centrosymmetric, but RP perovskites with phenylethylammonium (PEA) and 2-thiophenemethylammonium (TPMA) spacer cations display SHG. This work establishes multidimensional harmonic generation as a definitive method to measure SHG in halide perovskites.

Enhanced performance of CH3NH3PbI3 perovskite solar cells via interface modification using phenyl ammonium iodide derivatives

Interface modification in perovskite solar cells is a key factor for achieving high power conversion efficiency by suppressing electron-hole recombination and accelerating charge carrier extraction. Here, we use a series of phenyl ammonium derivatives, phenyl ammonium iodide (PAI), benzyl ammonium iodide (BAI), and phenyl ethyl ammonium iodide (PEAI), to modify the interface between methylammonium lead triiodide (MAPbI3) perovskite and Spiro-OMeTAD as a hole transport layer in solar cell devices. The structural and optical properties of the perovskite films are studied and the results reveal the formation of two-dimensional perovskite interfacial layers on the surface of the MAPbI3 film modified with PEAI and BAI whereas the MAPbI3 layer modified with PAI gives an interface layer with slightly different properties compared to the two-dimensional perovskite. Impedance spectroscopy shows that the charge transport resistance of the interface engineered solar cells decreases when compared to pristine MAPbI3. In addition, slower open-circuit voltage decay and longer carrier lifetime are also observed for the modified cells which in total lead to the improvement of the photovoltaic performance. The investigation therefore gives insight in the effect of interface modifications, and especially how different sizes of the molecular interface modifier results in different interface formation and characteristics.