Phenethylammonium Iodide Research Articles

2D/3D Heterostructure Halide Perovskite Thin Films through an Innovative Spray‐Deposition of Bulky Organic Cation‐Containing Ammonium Salts

AbstractHybrid halide perovskite involving low‐dimensional (2D or quasi‐2D) perovskites and their three‐dimensional (3D) counterparts provide long‐term stability in solar photovoltaics (PV) applications. Besides stability, perovskite PV commercialization would scalability in roll‐to‐roll fabrication of large‐area devices. Herein, it is reported on a pneumatic spray‐deposition methodology utilized to fabricate 2D/3D heterostructure perovskite films with tunable morphological and optical properties. Ammonium salts featuring bulky organic cations, such as phenethylammonium iodide (PEAI), 2‐thiophenemethylammonium iodide (TMAI), cyclohexylmethylammonium iodide (CMAI), and n‐dodecylammonium iodide (DDAI) are spray‐deposited on top of 3D‐formamidinium lead triiodide (3D‐FAPbI3) perovskite thin films, to synthesize a series of 2D perovskites, including (PEA)2FAPb2I7, (TMA)2PbI4, (CMA)2FAPb2I7, and (DDA)2FAPb2I7. X‐ray diffraction (XRD) and grazing incidence wide‐angle X‐ray scattering measurements confirm the evolution of 2D perovskite layer with distinct crystal structure and dimensionality (n = 1 and 2). Additionally, field‐emission scanning electron microscopy reveals diverse surface morphologies achievable in the 2D perovskite layers. Hyperspectral photoluminescence mapping further demonstrates that the emission at ≈566–570 nm corresponds exclusively to the 2D perovskite phase with n = 2. This study advances the development of 2D/3D heterostructure perovskites using bulky organic cations and underscores the potential of pneumatic spray‐deposition as a scalable fabrication technique for producing next‐generation optoelectronic devices.

Enhancing efficiency through surface passivation of carbon-based perovskite solar cells

Perovskite solar cells (PSCs) have made significant strides in power conversion efficiency (PCE), but their commercialization remains limited by stability issues. Additionally, the high cost of electrodes like gold necessitates the exploration of more affordable alternatives such as carbon (graphene). In this study, we present an approach that combines material dimensionality control and interfacial passivation using post-device treatment with phenethylammonium iodide (PEAI), an organic halide salt, to enhance the efficiency of carbon-based PSCs. Effective defect passivation is key to further improving the PCE and open-circuit voltage (VOC) of PSCs. Our results show that PEAI successfully passivates defects on the perovskite surface, significantly reducing non-radiative recombination. As a result, we achieved carbon-based PSCs with an impressive efficiency of 19.3%, demonstrating excellent stability under maximum power point tracking (MPPT) for over 900 h.

Impact of Self-Assembled Monolayer Structural Design on Perovskite Phase Regulation, Hole-Selective Contact, and Energy Loss in Inverted Perovskite Solar Cells

Recent studies have shown that self-assembled molecule (SAM)-based hole-selective contacts (HSCs) offer a promising solution to the challenges faced by perovskite solar cells (PVSCs), including minimal material consumption, scalable production, high interface stability, and the use of environmentally friendly solvents. In this study, the efficacy of two designs of SAMs (Cz and PA) as HSCs in inverted PVSCs was investigated by comparing them with the conventional MeO-2PACz (MeO) SAM. Surface analyses showed that the surface of PA is smoother than that of Cz, which helps to reduce interfacial defects. Subsequent perovskite deposition exhibited a reduced formation of the PbI2 phase, incidiating that its phase modulation ability is superior to that of MeO. Further analyses demonstrate the superior charge extraction ability of PA as a result of reduced interfacial defects and non-radiative recombination at the HSC/perovskite interface. By further coupling with phenethylammonium iodide (PEAI) surface passivation, both interfaces of the perovskite film were optimized and the inverted ((FAPbI3)0.85(MAPbBr3)0.15)0.95(CsPbI3)0.05 (bandgap = 1.62eV) PVSC achieves a high power conversion efficiency (PCE) of 23.3% and a very high open-circuit voltage of 1.227V due to the largely reduced energy loss. In addition, the PA PVSC exhibits enhanced long-term thermal stability at 85°C in a nitrogen atmosphere.

Defect passivation engineering for achieving 4.29% light utilization efficiency MA-free wide-bandgap semi-transparent perovskite solar cells

Wide-bandgap perovskite materials are a great candidate for semitransparent perovskite solar cells (ST-PSCs) due to their tunable bandgap, outstanding transparency, and excellent photovoltaic performance. Though Br-rich perovskite can widen the bandgap, Br influences the crystallization dynamic speed leaving small perovskite grain sizes and high defects. Surface passivation engineering has been one of the best choices to suppress defects caused by the rapid crystallization of Br-rich perovskites. Herein, we applied MA-free perovskite as a light absorber because of the erratic thermal aging of MA-containing perovskites and selected phenethylammonium iodide (PEAI) and 4-trifluoro phenylethylammonium iodide (CF3PEAI) as passivation materials for improving the performance of opaque PSCs and ST-PSCs. Consequently, CF3PEA possesses a larger dipole moment. It has been demonstrated to exhibit a stronger binding energy with the substrate than PEA by density functional theory (DFT) calculations. This enhanced molecular interaction underpins the performance improvements in our solar cells, which manifests as an inverted planar structure opaque PSCs with 1.78 eV bandgap achieve a power conversion efficiency (PCE) of 17.09 % with excellent stability. A PCE of 17.17 % with 25 % average visible-light transmittance (AVT) and 4.29 % light utilization efficiency (LUE) of ST-PSCs is achieved by further optimizing the fabrication process of the buffer layer for protecting the perovskites from the damage of ITO sputter. Meanwhile, a four-terminal tandem solar cell with ST-PSC and silicon-based passivated emitter rear cell (PERC) obtains a PCE of 26.28 %. This work provides a feasible way to fabricate high-performance ST-PSCs with limited materials and preparation conditions.

PEAI Surface Treatment for Low Ion Migration and High-Performance FAPbBr3 Single-Crystal X-ray Detectors.

Organometal halide perovskite single crystals (SCs) are the most promising candidates for the next generation of radiation detection materials. However, surface defects severely affect their detection performance and limit further applications. Here, we identified the surface defect types of FAPbBr3 SCs and employed phenethylammonium iodide (PEAI) solution to treat the crystal surface and to investigate their effects on ion migration, photoelectric performance, and X-ray detection performance. Our experimental results demonstrated that the surface defects, such as the metallic Pb and Br vacancies, can be effectively passivated by both the PEAI and the two-dimensional (2D) PEA2PbI4 layers. The PEAI layer can elongate the carrier lifetime, lower the trap density, and suppress ion migration in FAPbBr3 SCs. The 2D PEA2PbI4 layer can form a dense and full surface coverage, suppress ion migration, and lower the dark current of the SCs. The X-ray sensitivity of the PEAI-passivated FAPbBr3 SC detectors is 227.93 μCGyair-1 cm-2, which is an order of magnitude higher than that of the pristine FAPbBr3 SC detectors. This work demonstrates that surface treatment plays a critical role in the crystal quality and the X-ray detection performance of SCs.

Bilayer interface engineering through 2D/3D perovskite and surface dipole for inverted perovskite solar modules

The persistency of passivation and scalable uniformity are vital issues that limit the improvement of performance and stability of large-area perovskite solar modules (PSMs). Here, we design a bilayer interface engineering strategy that takes advantage of the stability and passivation ability of low-dimensional perovskite and the dipole layer. Introducing phenethylammonium iodide (PEAI) can form 2D/3D heterojunctions on the perovskite surface and effectively passivate defects of perovskite film. Interestingly, the upper piperazinium iodide (PI) layer can still form surface dipoles on the 2D/3D perovskite surface to optimize energy-level alignment. Moreover, the bilayer interface engineering enables large-area perovskite films with uniform surface morphology, lower trap-state density and stability against environmental stress factors. The final devices achieved a small-area PCE of 25.20% and a large-area (1 cm2) PCE of 23.96%. A perovskite mini-module (5 × 5 cm2 with an active area of 14.28 cm2) could also be fabricated to achieve a PCE of 23.19%, ranking it among the highest for inverted PSMs. Additionally, the device could retain over 93% of its initial efficiency after MPP tracking at 45 °C for 1280 hours. This study successfully demonstrates a bilayer interface engineering with respective functions, offering valuable insights for producing efficient and stable large-area PSCs.

Unraveling Differences in the Effects of Ammonium/Amine-Based Additives on the Performance and Stability of Inverted Perovskite Solar Cells.

Additive engineering, with its excellent ability to passivate bulk or surface perovskite defects, has become a common strategy to improve the performance and stability of perovskite solar cells (PVSCs). Among the various additives reported so far, ammonium salts are considered an important branch. It is worth noting that although both ammonium-based additives (R-NH3 +) and amine-based additives (R-NH2) are derivatives of ammonia (NH3), the functions of the two can be easily confused due to their structural similarities. Moreover, there is no comprehensive comparative analysis of them in the literature. Here, the differences between phenethylammonium iodide (PEA+) and phenethylamine (PEA) additives are revealed experimentally and theoretically. The results clearly show that PEA outperforms PEA+ in terms of device performance and stability based on the following three factors: i) PEA's defect passivation capability is superior to that of PEA+; ii) PEA has better hydrophobicity to hinder water ingress; and iii) PEA completely improves the stability of PVSCs by enhancing thermal stability and inhibiting iodide migration in perovskite more effectively than PEA+. As a result, the power conversion efficiency (PCE) of the inverted methylammonium triiodide (MAPbI3) device using PEA increases by ≈15% to over 21%. More importantly, this device exhibits greater ability to prevent water invasion, thermal-induce degradation, and inhibit iodide ion migration, resulting in better long-term stability.

Enhanced Quantum Efficiency of Near-IR Perovskite Light Emitting Diodes Via Dual Interfacial Modification

Near-infrared (NIR) light-emitting diodes play a crucial role in a wide range of applications, including sensors, night vision displays, security systems, medicine, spectroscopy, and military applications. The potential for high-performance NIR perovskite light-emitting diodes (NIR-PeLEDs) has been highlighted with the impressive advancement of fluorescent perovskite thin films. These PeLEDs exhibit promising features such as a tunable band gap, high color purity, and low non-radiative recombination rates. Despite these advantages, the current state-of-the-art NIR-PeLEDs faces challenges primarily related to poor film quality and increased defect states, leading to limitations in external quantum efficiency (EQE) and operational stability. In addressing these issues, we present a novel dual interfacial modification approach involving the incorporation of fluorinated phenethylammonium iodide (F-PEAI), a bulky organic cation, at both the bottom and top interfaces of perovskite emitting films. The modified interfaces result in perovskite films with a smoother surface morphology, complete coverage, and high crystallinity, leading to a red-shifted fluorescence band extending toward 800 nm. Furthermore, the introduction of F-PEAI facilitates the formation of compact and fine grains in perovskite films, contributing to an enhanced photoluminescence quantum yield (PLQY). Consequently, NIR-PeLEDs modified with F-PEAI demonstrate improved EQE values coupled with enhanced operational stability. The combination of electrical, optical, and physical analyses of both films and devices underscores the effectiveness of the dual interface modification in developing efficient NIR perovskite LEDs suitable for practical applications.

Phenylethylammonium iodide induced “in situ healing” behavior for carbon-electrode basing, hole-conductor-free perovskite solar cells

Previous study showed that blending octylammonium iodide (OAI) in a carbon paste induced a kind of in situ healing effect for carbon-electrode basing, hole-conductor-free, planar perovskite solar cells. Here, the strategy is re-examined by considering another kind of ammonium halide molecule or phenethylammonium iodide (PEAI). It is observed that, after moderate PEAI blending, power conversion efficiency of devices rises from 11.56 (±0.82)% to 15.77 (±0.53)% (championed at ∼17.9%), with open-circuit voltage increasing from 969 (±28) to 1033 (±13) mV, and fill factor increasing from 51.17 (±2.68)% to 65.71 (±1.36)%. The improved device efficiency is due to the retarded charge recombination and the improved charge transfer processes. Transient photovoltage/photocurrent decay curve tests show that, after PEAI blending, lifetime of charge carriers in device increases from 3.21 to 5.67 μs, while the charge extraction time decreases from 2.99 to 2.18 μs. Moreover, built-in potential rises according to the Mott–Schottky study. A designated “penetration-reaction” test reveals that PEAI could also induce the in situ healing effect, which accounts for the improved charge transfer/recombination processes. The study could tell the universality of this strategy to certain extent.

Peptide‐Based Ammonium Halide with Inhibited Deprotonation Enabling Effective Interfacial Engineering for Highly Efficient and Stable FAPbI3 Perovskite Solar Cells

AbstractAmmonium iodides are intensively investigated as effective interfacial passivation agents in perovskite solar cells (PSCs) while facing a major challenge of their high reactivity with perovskites that undermines the operational stability of the PSCs. Exemplified by involving rationally designed/selected peptide into the widely adopted phenethylammonium iodide (PEAI), the present work demonstrates that the bespoke peptide‐PEAI can effectively inhibit the deprotonation of ammonium iodides and thus hinder the formation of 2D perovskite, facilitating the stability enhancement in perovskite films by multi hydrogen bonding. The additional lone pair electrons provided by peptide molecules can also enhance the passivation ability of the modified layer. Attributed to the stable co‐modifier peptide‐PEAI, the small‐area FAPbI3‐based PSCs yield a high efficiency of 25.02% with robust light and thermal stabilities. Moreover, the peptide‐PEAI‐based minimodules with an efficiency of 19.06% for a total area of 36 cm2 manifested the great application potential of this co‐modification strategy in the perovskite photovoltaics.

Investigation of the Effect of the Passivation on the Charge Transfer from MAPbI3 to Electron Transport Layer Using a Heterodyne Transient Grating Spectroscopic Technique.

We fabricated MAPbI3 perovskite thin films with ZnO on a glass substrate, in which a passivation layer (Phenethylammonium iodide (PEAI); p-methoxyphenethylammonium iodide (CH3O-PEAI); 2-methoxyethylammonium iodide (MEAI)) was inserted between two layers. In order to understand the effect of the insertion of each passivation material on the transfer efficiency of the photo-generated electrons from MAPbI3 to ZnO, we observed the near-field heterodyne transient grating (NF-HD-TG) responses of each film and investigated the component arising from the recombination of the trapped electrons at the ZnO surface. Based on the accelerated recombination between photo-generated holes remaining in the MAPbI3 layer and surface-trapped electrons in ZnO and the increase in the number of the trapped electrons in ZnO when either CH3O-PEAI or PEAI was applied, we successfully revealed that the charge transfer efficiency was enhanced by the insertion of the passivation materials including a benzene ring stabilizing the defect states. Particularly, it was demonstrated that CH3O-PEAI showed the highest increase in the charge transfer efficiency, which could be attributed to the high electron density in the benzene ring, resulting from the existence of the electron donating group, CH3O, and its role in the effective transition from 3D to 2D perovskite phases.

Regulating the perovskite/C60 interface via a bifunctional interlayer for efficient inverted perovskite solar cells

Inverted perovskite solar cells are promising candidates in photovoltaic fields due to their low-temperature processing, simplified fabrication, and enhanced stability when compared with the conventional configuration. However, the significant non-radiative recombination losses and energy alignment mismatch at the perovskite/C60 interface limit the device's performance and long-term stability. To overcome this drawback, we introduced trifluoromethoxy-functionalized phenethylammonium iodide salts with high polarity between the perovskite and C60 electron transporting layer. This bifunctional interlayer not only effectively passivates the perovskite surface and interface but also reduces the minority carriers through the band rearrangement at this interface, thus significantly suppressing the deteriorating interfacial non-radiative recombination. The modified interlayer also facilitates electron extraction by reducing the offset between the perovskite and C60, contributing to an improved photocurrent and fill factor. The resultant inverted perovskite solar cell based on a Cs0.05FA0.85MA0.10Pb(I0.95Br0.05)3 composition reveals a power conversion efficiency of 24.7 % at the reverse scan and shows negligible efficiency loss after 600 h of maximum power point tracking under one-sun illumination. Overall, this feasible deposition of ammonium-based interlayer establishes a successful demonstration of efficient and stable inverted devices to accelerate the commercialization of perovskite photovoltaics.

Modified surface ligand management of CsPbI3 perovskite quantum dots enables efficient and stable electroluminescent solar cells

Solution-processed CsPbI3 perovskite quantum dots (PQDs) have attracted enormous attention in both photovoltaic and electroluminescent applications in recent years. However, the surface defects of CsPbI3 PQDs in the ligand exchange procedure still suffer the challenge of imperfect passivation, leading to poor device performance and ambient stability. In this work, we propose a modified surface ligand management to deposit CsPbI3 PQD films using a layer-by-layer (LBL) solid-state exchange strategy, and its applications in photovoltaic and electroluminescent devices are studied. The conjugated phenethylammonium iodide (PEAI) ligand, acting as a short-chain ligand with a phenyl group (PEA+ ion) for encapsulating the CsPbI3 PQDs during the LBL procedure, which can both realize enhanced inter-dot coupling and defects passivation compared with conventional post-treatments. We further demonstrate the balanced transport and injection of electrons and holes within the PEAI-LBL based CsPbI3 PQD films. With this approach, the CsPbI3 PQD solar cells based on PEAI-LBL yielded a champion power conversion efficiency (PCE) of up to 14.18% with a high open voltage of 1.23 V, along with obviously electroluminescent red emission properties in one device. Meanwhile, the unencapsulated devices exhibited excellent stability under a high-humidity environment. This strategy should accelerate advancement in utilizing PQDs for bifunctional optoelectronic applications.

A comparative study of surface passivation of p-i-n perovskite solar cells by phenethylammonium iodide and 4-fluorophenethylammonium iodide for efficient and practical perovskite solar cells with long-term reliability

Passivation of the defective surface in perovskite absorber layers effectively stabilizes the photovoltaic performance and electronic properties of perovskite solar cells (PSCs). We herein investigated the passivating effects of phenethylammonium iodide (PEAI) and 4-fluorophenethylammonium iodide (F-PEAI) on perovskite absorber layers comparatively, analyzing their impact on morphological, optical, and electrical properties of perovskite absorbers. Both passivation molecules significantly improved film characteristics, with enlarged domain size, uniform surface morphologies, and prolonged carrier lifetime observed in polycrystalline perovskite absorbers. Notably, non-fluorinated PEAI demonstrated superior effectiveness in reducing tail states and defective Pb2+ sites, resulting in more stable absorbers with fewer defects. The passivated perovskite absorbers exhibited higher champion efficiencies (22.07% for PEAI and 20.56% for F-PEAI) compared to control devices (19.53%), attributed to the suppression of interfacial nonradiative recombination and reduction in recombination energy losses. The devices with passivated perovskite absorbers also demonstrated promising indoor photovoltaic performance, achieving an efficiency of 39.04% and 37.02% under dim-light conditions (LED, 6500 K, 1000 Lux), compared to 29.43% in the control device. Importantly, the passivated absorbers maintained 94% of their initial efficiency even after 1250 hours of humidity aging, indicating enhanced hydrophobicity and reduced trap states, resulting in good ambient stability. Our findings highlight the effectiveness of passivation techniques using organic ammonium halide salts in improving the efficiency and stability of perovskite solar cells.

Understanding and Mitigating Atomic Oxygen-Induced Degradation of Perovskite Solar Cells for Near-Earth Space Applications.

Combining high efficiency with good radiation tolerance, perovskite solar cells (PSCs) are promising candidates to upend expanding space photovoltaic (PV) technologies. Successful employment in a Near-Earth space environment, however, requires high resistance against atomic oxygen (AtOx). This work unravels AtOx-induced degradation mechanisms of PSCs with and without phenethylammonium iodide (PEAI) based 2D-passivation and investigates the applicability of ultrathin silicon oxide (SiO) encapsulation as AtOx barrier. AtOx exposure for 2h degraded the average power conversion efficiency (PCE) of devices without barrier encapsulation by 40% and 43% (w/o and with 2D-PEAI-passivation) of their initial PCE. In contrast, devices with a SiO-barrier retained over 97% of initial PCE. To understand why 2D-PEAI passivated devices degrade faster than less efficient non-passivated devices, various opto-electrical and structural characterications are conducted. Together, these allowed to decouple different damage mechanisms. Notably, pseudo-J-V curves reveal unchanged high implied fill factors (pFF) of 86.4% and 86.2% in non-passivated and passivated devices, suggesting that degradation of the perovskite absorber itself is not dominating. Instead, inefficient charge extraction and mobile ions, due to a swiftly degrading PEAI interlayer are the primary causes of AtOx-induced device performance degradation in passivated devices, whereas a large ionic FF loss limits non-passivated devices.

Fabrication of [001]‐Oriented FAPbI3‐Based Photodetector With Excellent Air Stability Via Green Anti‐Solvent Additive Engineering

AbstractFormamidinium lead triiodide (FAPbI3) exhibits excellent thermal and chemical stability, making it a suitable alternative for methylammonium lead triiodide (MAPbI3) in high‐performance photodetectors. However, FAPbI3 faces the challenge of transforming from the metastable photoactive black phase α‐FAPbI3 to the photoinactive yellow phase δ‐FAPbI3 at room temperature. This phase transition is accelerated in humid atmospheric conditions. To realize high‐performance FAPbI3‐based photodetectors, it is crucial to form stable and highly crystalline phase‐pure α‐FAPbI3 films. Herein, is fabricate highly stable and crystalline FAPbI3 films and photodetectors through anti‐solvent additive engineering (AAE) using a green anti‐solvent (isopropanol, IPA) and an organic spacer (phenethylammonium iodide, PEAI). It is found that PEAI‐AAE treatment induced [001]‐preferred orientation growth in FAPbI3 films, and passivated defects within the crystal. The photodetectors based on PEAI‐AAE‐treated FAPbI3 film exhibits a fast response time of 485 µs/525 µs (rise time/fall time), high responsivity of 24.89 A W−1, and excellent specific detectivity of 1.56 × 1013 Jones. Moreover, the PEAI‐AAE‐treated FAPbI3 photodetector retained over 80% of its initial performance even after exposure to ambient air for over 720 h, demonstrating excellent long‐term stability. This study provides a green processing method that paves the way for future commercialization of perovskite‐based optoelectronic devices.

Elevated efficiency and stability of hole-transport-layer-free perovskite solar cells induced by phenethylammonium iodide

Despite organic–inorganic hybrid perovskite devices having reached a photoelectric conversion efficiency (PCE) of 26.1%, their high cost and poor stability limit their industrial applications.

Perovskite solar cell technology scaling‐up: Eco‐efficient and industrially compatible sub‐module manufacturing by fully ambient air slot‐die/blade meniscus coating

AbstractThe efficiency gap between perovskite (PVSK) solar sub‐modules (size ≥200 cm2) and lab scale cells (size ˂1 cm2) is up to 36%. Moreover, the few attempts present in the literature used lab‐scale techniques in a glove‐box environment, reducing its compatibility for further product industrialization. Here, we report a PVSK sub‐module (total area 320 cm2, aperture area 201 cm2, 93% geometrical fill factor [GFF]) fabricated in ambient air by hybrid meniscus coating techniques assisted by air and green antisolvent quenching method. To suppress nonradiative recombination losses, improve carrier extraction and control the PVSK growth on such a large surface, we adopted phenethylammonium iodide (PEAI) passivation and PVSK solvent addiction strategies. The high homogeneous and reproducible layers guarantee an efficiency of 16.13% (7% losses with respect to the small area cell and zero losses with respect to the mini‐modules) and a stability of more than 3000 h according to International Summit on Organic PV Stability, dark storage/shelf life in ambient (ISOS‐D‐1). The sustainability of used methods and materials is demonstrated by the life cycle assessment. The scale‐up operation allows for strong impact mitigation in all the environmental categories and more efficient consumption of the resources. Finally, the economic assessment shows a strong cost reduction scaling from mini‐ to sub‐module (about 40%).

A Fluorinated Phenethylammonium‐Based Spacer Cation Prompts the Spontaneous Formation of Gradient 2D/3D Perovskites for Efficient and Stable Solar Cells

Despite the prominent photovoltaic performance and broad application prospect of perovskite solar cells (PVSCs), a significant challenge for their commercialization is the stability issue. Herein, a fluorinated organic ammonium salt, 4‐trifluoromethyl phenethyl ammonium iodide (4FPAI), is utilized for the spontaneous formation of gradient 2D/3D perovskite which can be prepared by a simple one‐step spin‐coating process with low‐dimensional phases on the surface and high‐dimensional phases at the bottom. The introduction of 4FPAI leads to improved charge transport as well as reduced nonradiative recombination. The optimal 4FPAI‐based PVSC exhibits a power conversion efficiency (PCE) of 22.12% which is higher than that of the control PVSC without the 4FPAI treatment (20.87%). Meanwhile, the encapsulated 4FPAI‐based device remains at about 88% of its initial PCE under ambient air exposure for 80 days, demonstrating its improved moisture resistance compared to the reference device. This work provides an important strategy for fabricating high efficiency and long‐term stable 2D/3D PVSCs.

High-Mobility and Bias-Stable Field-Effect Transistors Based on Lead-Free Formamidinium Tin Iodide Perovskites.

Electronic devices based on tin halide perovskites often exhibit a poor operational stability. Here, we report an additive engineering strategy to realize high-performance and stable field-effect transistors (FETs) based on 3D formamidinium tin iodide (FASnI3) films. By comparatively studying the modification effects of two additives, i.e., phenethylammonium iodide and 4-fluorophenylethylammonium iodide via combined experimental and theoretical investigations, we unambiguously point out the general effects of phenethylammonium (PEA) and its fluorinated derivative (FPEA) in enhancing crystallization of FASnI3 films and the unique role of fluorination in reducing structural defects, suppressing oxidation of Sn2+ and blocking oxygen and water involved defect reactions. The optimized FPEA-modified FASnI3 FETs reach a record high field-effect mobility of 15.1 cm2/(V·s) while showing negligible hysteresis. The devices exhibit less than 10% and 3% current variation during over 2 h continuous bias stressing and 4200-cycle switching test, respectively, representing the best stability achieved so far for all Sn-based FETs.