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The morphology of perovskite films with and without DIAI. a) AFM images, b) SEM images, c) grain size distributions, and d) contact angles (bulk and surface double‐treated is marked as ++, bulk‐passivated is marked as bulk, and surface‐modified is marked as surface).
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With its power conversion efficiency surpassed those of all other thin film solar cells only a few years after its invention, the perovskite solar cell has become a superstar. Controlling intermediate phase of crystallization is a key to obtain high‐quality perovskite films. Herein, a single molecule additive, N, N‐Dimethylimidodicarbonimidic diami...
Citations
... The MHPs have been widely studied due to their large optical absorption coefficient, 21 high photoelectric conversion efficiency, 22 and large spin diffusion length. 23 In recent years, MHPs have also attracted wide attention in spintronic devices, such as spin-LEDs and spin valves. ...
Metal halide perovskites (MHPs) have attracted wide interest in spintronics. In addition, they also perform various spin–orbit coupling (SOC) strength due to their complex crystal structures. The control of SOC strength has been an increasingly prevalent topic for the manipulation of the spin degree in spintronic devices. Here, we fabricate MAPbI3 films possessing cubic crystal phase and tetragonal crystal phase with Pb vacancies. Circular photogalvanic effect (CPGE) measurements indicate that CN, representing the difference between right and left circularly polarized photocurrents, of the tetragonal structure with Pb vacancies (CN = 0.6316) is almost three orders of magnitude larger than that of the cubic structure (CN = 0.0009). Combining with the density functional theory calculations, we confirm that the strength of SOC generating the CPGE could be tuned by crystal phases of MAPbI3, and the existence of Pb vacancies could remarkably enhance the spin splitting of the band structure. Our finding provides a possible way for clarifying various puzzling SOC performances in MHPs and paves the way for spintronic device applications and circularly polarized photoelectric detectors by controlling the crystal phases and defects.
... Perovskite solar cells (PSCs) have garnered significant attention due to their straightforward fabrication process, high carrier mobility, long carrier diffusion length, and strong optical absorption coefficient [1][2][3][4][5][6]. These perovskite materials are widely recognized as one of the most promising next-generation solar materials [7][8][9][10][11]. ...
SnO2 has attracted much attention due to its low-temperature synthesis (ca. 140 °C), high electron mobility, and low-cost manufacturing. However, lattice mismatch and oxygen vacancies at the SnO2/CsPbI3−xBrx interface generally lead to undesirable nonradiative recombination in optoelectronic devices. The traditional TiO2 used as the electron transport layer (ETL) for all-inorganic perovskite solar cells (PSCs) requires high-temperature sintering and crystallization, which are not suitable for the promising flexible PSCs and tandem solar cells, raising concerns about surface defects and device uniformity. To address these challenges, we present a bilayer ETL consisting of a SnO2 layer using electron beam evaporation and a TiO2 layer through the hydrothermal method, resulting in an enhanced performance of the perovskite solar cell. The bilayer device exhibits an improved power conversion efficiency of 11.48% compared to the single-layer device (8.09%). The average fill factor of the bilayer electron transport layer is approximately 15% higher compared to the single-layer electron transport layer. Through a systematic investigation of the use of ETL for CsPb3−xBrx PSCs on optical and electronic properties, we demonstrate that the SnO2/TiO2 is an efficient bilayer ETL for PSCs as it significantly enhances the charge extraction capability, suppresses carrier recombination at the ETL/perovskite interface, facilitates efficient photogenerated carrier separation and transport, and provides high current density and reduced hysteresis.
... The HPTS-processed FAPbI3 films show smaller roughness than the control film. The smaller roughness reveals that the interface contact between the hole transport layer and the perovskite layer is improved and can facilitate carrier extraction [46,47]. ...
Formamidinium lead triiodide (FAPbI3) is considered as the prospective light-absorbing layer on account of the close-to-ideal bandgap of the α-phase, wide optical absorption spectrum and good thermal stability. Therefore, how to realize δ to α-phase transition to obtain phase-pure α-FAPbI3 without additives is important for FAPbI3 perovskite films. Herein, a homologous post-treatment strategy (HPTS) without additives is proposed to prepare FAPbI3 films with pure α-phase. The strategy is processed along with dissolution and reconstruction process during the annealing. The FAPbI3 film has tensile strain with the substrate, and the lattice keeps tensile, and the film maintains in an α/δ hybrid phase. The HPTS process releases the tensile strain between the lattice and the substrate. The process of strain release realizes the phase transition from δ to α-phase during this process. This strategy can accelerate the transformation from hexagonal δ-FAPbI3 to cubic α-FAPbI3 at 120℃. As a result, the acquired α-FAPbI3 films exhibit better film quality in optical and electrical properties, accordingly achieving device efficiency of 19.34% and enhanced stability. This work explores an effective approach to obtain additive-free and phase-pure α-FAPbI3 films through a homologous post-treatment strategy to fabricate uniform high-performance α-FAPbI3 perovskite solar cells.
... [8,9] Various strategies such as component engineering, additive engineering, and interlayer design have been developed to extend device lifetime. [10][11][12][13] In particular, the incorporation of bulky and hydrophobic organic spacer cations to reduce perovskite dimensionality shows great potential to prolong device lifetime. [14][15][16] Low-dimensional structures achieve an impressive environmental stability by locking [PbX 6 ] 4À octahedra and blocking moisture and oxygen attack. ...
... Thus the intensity of ground-state bleaching (GSB) signal responds to charge density and its kinetic evolution is closely related to the carrier dynamics. [10,47,48] Figure S12 shows the pseudocolor map of perovskite films, which is a function of wavelength and delay time. We traced the evolution of maps with a delay time of up to 7200 ps. ...
Although the incorporation of 2D perovskite into 3D perovskite can greatly enhance intrinsic stability, power conversion efficiency (PCE) of 2D/3D perovskite is still inferior to its 3D counterpart due to poor carrier transport kinetics resulted from the quantum and dielectric confinement of 2D component. To overcome this issue, the electron acceptor molecule 1,2,4,5‐tetracyanobenzene (TCNB) was introduced to trigger intermolecular π–π interaction in 2D perovskite along with the electronic doping of 2D/3D perovskite to improve charge transfer efficiency. By virtue of high electron affinity, TCNB can undergo electron transfer reaction and subsequently establish π–π interaction with 1‐naphthalenemethylammonium (NMA) cations, greatly strengthening lattice rigidity and reducing exciton binding energy. Transmission electron microscopy results demonstrate that 2D phases are mainly distributed at grain boundaries, reducing defect density and weakening nonradiative recombination. Meanwhile, the p‐type doping of perovskite by TCNB optimizes energy level alignment at perovskite/hole transport layer interface. Consequently, PCE of champion device is significantly boosted to 24.01 %. The unencapsulated device retains an initial efficiency close to 94 % after exposure to ambient environment for over 1000 h. This work paves a novel path for designing new mixed‐dimensional perovskite solar cells with high PCE and superior stability.
Here we report a new type of CsPbI 3 ‐based two‐dimensional (2D) Dion‐Jacobson (DJ) perovskites, featuring a general formula of (PDMA)Cs n‐1 PbnI 3n+1 (n = 1, 2, 3, 4) with 1,4‐phenylenedimethanammonium (PDMA) as the organic spacer cation. The crystal structure, optical and electric properties, and surface morphology of the perovskite films are fully surveyed. The solar cell device based on the n = 4 film delivers a champion power conversion efficiency (PCE) of 11.27%, further improved to 12.61% by treating with the PDMA molecules. The PDMA passivation suppresses non‐radiative recombination, extends charge carrier lifetime, and reduces open‐circuit voltage loss. A gradient energy level near the film surface facilitates electron extraction, alleviating charge accumulation. The PDMA molecules form a protective layer, inhibiting water infiltration and enhancing stability. The optimized device exhibits excellent shelf stability with no PCE decay after 110 days. This study introduces a dual‐functional molecule as a new DJ‐type spacer and an effective passivation agent for efficient and stable CsPbI 3 ‐based 2D perovskite solar cells.
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The tricyclic alkaloid colchicine is applied to catalyzed crystallization (CC) of high-quality α-FAPbI 3 perovskite film in the one-step antisolvent-free process for high performance perovskite solar cells.
Spiro‐OMeTAD, as a crucial component of the hole‐transporting layer, exhibits limited mobility and conductivity, and the Li‐TFSI dopant is sensitive to water vapor, which imposed restrictions on the photovoltaic efficiency and durability of perovskite solar cells (PSCs). In this work, the iron‐porphyrin (FePP) molecule is introduced into Spiro‐OMeTAD solution as additive, which facilitate the oxidation process of Spiro‐OMeTAD, leading to the enhancement of hole mobility and hole extraction and transport. Besides, the surface Pb ²⁺ defects in the perovskite film are cured by the presence of carboxylic acids (‐COOH) in FePP. As a result, the photovoltaic properties of PSCs with FePP additive have been improved in all aspects, and a PCE of 21.58% can be achieved. Moreover, the FePP additive can further anchor the Li ⁺ ions in HTL to prevent it from being invaded by water vapor. Dramatically, the degradation of unencapsulated devices is suppressed significantly, the device with FePP additive retain 82.0% of its original PCE under 10‐20% RH after 7100 h, and maintain about 79.6% of its original PCE under 50‐60% RH after 1000 h. Thus, this study shows that the design and development of multifunctional HTL additives holds great potential for achieving highly efficient and durable PSCs.
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Developing an additive to effectively regulate the perovskite crystallization kinetics for the optimized optoelectronic properties of perovskite film plays a vital role in obtaining high efficiency and stable perovskite solar cells (PSCs). Herein, a new additive is designed and directly synthesized in perovskite precursor solution by utilizing an addition reaction between but‐3‐yn‐1‐amine hydrochloride (BAH) and formamidinium iodide. It is found that its product may control the intermediate precursor phase for regulating perovskite nucleation, leading to advantageous 2D perovskite to induce growth of perovskite along the preferred [001] orientation with not only released lattice strain but also strong interaction with perovskite to passivate its surface defects. By taking advantage of the above synergistic effects, the optimized PSC delivers an efficiency of 25.19% and a high open‐circuit voltage (VOC) of 1.22 V. Additionally, the devices demonstrate good stability, remaining over 90% of their initial efficiencies under ambient atmosphere conditions for 60 days, high temperature of 85 °C for 200 h, or maximum power point tracking for 500 h.
