Thin films of CdS and CdS:O were deposited using RF magnetron sputtering at room temperature and at 270 °C in sputtering ambient with 0-4% O 2 (balance Ar). These films were characterized with ...respect to their optical and structural properties. The samples were then subjected to a heat treatment similar to that experienced during CdTe closed space sublimation deposition, after which the samples were re-characterized.
Despite the swift rise in power conversion efficiency (PCE) to more than 32%, the instability of perovskite/silicon tandem solar cells is still one of the key obstacles to practical application and ...is closely related to the residual strain of perovskite films. Herein, a simple surface reconstruction strategy is developed to achieve a global incorporation of butylammonium cations at both surface and bulk grain boundaries by post‐treating perovskite films with a mixture of N,N‐dimethylformamide and n‐butylammonium iodide in isopropanol solvent, enabling strain‐free perovskite films with simultaneously reduced defect density, suppressed ion migration, and improved energy level alignment. As a result, the corresponding single‐junction perovskite solar cells yield a champion PCE of 21.8%, while maintaining 100% and 81% of their initial PCEs without encapsulation after storage for over 2500 h in N2 and 1800 h in air, respectively. Remarkably, a certified stabilized PCE of 29.0% for the monolithic perovskite/silicon tandems based on tunnel oxide passivated contacts is further demonstrated. The unencapsulated tandem device retains 86.6% of its initial performance after 306 h at maximum power point (MPP) tracking under continuous xenon‐lamp illumination without filtering ultraviolet light (in air, 20–35 °C, 25–75%RH, most often ≈60%RH).
A surface reconstruction strategy is employed to achieve a strain‐free perovskite film with simultaneously reduced defect density, suppressed ion migration, and improved energy level alignment. The resultant monolithic perovskite/black‐silicon tandem realizes a certified stabilized efficiency ≈29.0%, which is among the best performances for perovskite/silicon tandems based on tunnel oxide passivated contacts.
Hybrid organic-inorganic lead halide perovskite solar cells have shown a remarkable rise in power conversion efficiency over a short period of time; however, long-term stability remains a key ...challenge hindering the practical application of these cells. Here, we report an approach to sequentially apply a typical one-step solution formulation—self-seeding growth (SSG)—to realize high-quality perovskite thin films with reduced defect density, fewer apparent grain boundaries, improved charge-carrier transport and lifetime, and enhanced hydrophobicity for enhanced stability. Using FA-MA-Cs-based perovskite, SSG devices showed improved efficiency from 17.76% (control) to 20.30% (SSG), with an unencapsulated device retaining >80% of its initial efficiency over 4,680-h storage in an ambient environment with high relative humidities. The SSG devices also exhibited much improved thermal and operational stabilities. In addition, SSG can be applied to different substrates and perovskite compositions, which makes it a viable method for preparing high-quality perovskite thin films for device applications.
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•Self-seeding growth (SSG) to realize high-quality perovskite films are developed•SSG devices show improved efficiency from 17.76% (control) to 20.30% (SSG)•Unsealed devices show better stability under high humidity, heat, and illumination•SSG approach can be applied to different substrates and perovskite compositions
The issue of poor long-term stability against moisture is still a key challenge hindering perovskite solar cells for practical applications. Here, we report an approach to sequentially apply a typical one-step solution formulation—self-seeding growth (SSG)—to realize high-quality perovskite thin films with reduced defect density, fewer apparent grain boundaries, improved charge-carrier transport and lifetime, and enhanced hydrophobicity for enhanced stability. Using FA/MA/Cs-based perovskite, SSG devices showed improved efficiency from 17.76% (control) to 20.30% (SSG), with an unencapsulated device retaining >80% of its initial power conversion efficiency over 4,680-h storage in an ambient environment with high relative humidity. In addition, SSG can be applied to different substrates (e.g., SnO2 versus TiO2; planar versus mesoporous) and perovskite compositions, making it a viable method for preparing high-quality perovskite thin films for device applications.
A general approach—self-seeding growth (SSG)—that utilizes a typical one-step perovskite precursor ink formulation to create perovskite active layer is reported and can be applied to different substrates and perovskite compositions for preparing high-quality perovskite thin films. Compared to the standard one-step solution-deposited devices, SSG perovskite thin films exhibit reduced defect density, fewer apparent grain boundaries, and improved charge-carrier transport and lifetime. The SSG devices present much improved performance along with better stability under high humidity, heat, and sun illumination.
We used Kelvin probe force microscopy to study the potential distribution on cross-section of perovskite solar cells with different types of electron-transporting layers (ETLs). Our results explain ...the low open-circuit voltage and fill factor in ETL-free cells, and support the fact that intrinsic SnO 2 as an alternative ETL material can make high-performance devices. Furthermore, the potential-profiling results indicate a reduction in junction-interface recombination by the optimized SnO 2 layer and adding a fullerene layer, which is consistent with the improved device performance and current-voltage hysteresis.
We have fabricated CdTe solar cells on commercial SnO 2 /SnO 2 :F coated soda-lime glass substrates using ZnS/CdS window layers with various thickness combinations. With our standard fabrication ...method, CdTe solar cells with ZnS/CdS window layers have exhibited efficiencies as high as 12.3% under AM1.5 illumination. However, the efficiencies of the cells with ZnS/CdS window layers are still lower than the reference CdTe cells with CdS window layer (13%). We found that optimizing the thickness combination and heat treatment of the ZnS/CdS window layers prior to CdTe deposition may be a viable approach to optimize the performance of CdTe solar cells with ZnS/CdS window layers.
A key pathway to meeting the Department of Energy SunShot 2020 goals is to reduce financing costs by improving investor confidence through improved photovoltaic (PV) module reliability. A ...comprehensive approach to further understand and improve PV reliability includes characterization techniques and modeling from module to atomic scale. Imaging techniques, which include photoluminescence, electroluminescence, and lock-in thermography, are used to locate localized defects responsible for module degradation. Small area samples containing such defects are prepared using coring techniques and are then suitable and available for microscopic study and specific defect modeling and analysis.
This communication presents our recent discovery on electrochemically induced fracture behavior of a single-crystal silicon (Si) anode, with particular focus on the initialization and propagation of ...cracks. Intensive efforts have investigated mechanical properties and cracking behavior of Si electrodes overextended electrochemical cycles. However, it is still elusive how cracks nucleate and propagate in the crystalline Si anodes at the very early stage. Here, we examined the morphology evolution of the Si (100) wafer electrodes during the first electrochemical cycle, and we found that the formation of -oriented buckles—induced by the anisotropic lithiation in crystalline Si during 1st lithiation—results in cracks propagated along the direction in the buckled region during 1st delithiation. Surprisingly, as the delithiation proceeds, new cracks oriented along the direction appear in the intact area where no macroscopic deformation occurred during the previous lithiation. The -oriented cracks have not been studied previously. Herein, we introduce a linear elastic fracture mechanics model to help understand underlying mechanisms for such crack propagation. The findings in this work provide significant insights into the fracture behavior and formation mechanism, as well as possible strategies to inhibit crack propagations of Si electrodes at the beginning stage of cycling.
•Electrochemical induced cracking behavior in amorphous LixSi layer.•Formation mechanism of the -oriented cracks and the -oriented cracks.•Using linear elastic fracture mechanics to investigate the -oriented cracks.
Despite rapid advancements in the photovoltaic efficiencies of perovskite solar cells (PSCs), their operational stability remains a significant challenge for commercialization. This instability ...mainly arises from light‐induced halide ion migration and subsequent oxidation into iodine (I2). The situation is exacerbated when considering the heat effects at elevated temperatures, leading to the volatilization of I2 and resulting in irreversible device degradation. Mercaptoethylammonium iodide (ESAI) is thus incorporated into perovskite as an additive to inhibit the oxidation of iodide anion (I−) and the light‐induced degradation pathway of FAPbI3→FAI+PbI2. Additionally, the formation of a thiol‐disulfide/I−‐I2 redox pair within the perovskite film provides a dynamic mechanism for the continuous reduction of I2 under light and thermal stresses, facilitating the healing of iodine‐induced degradations. This approach significantly enhances the operational stability of PSCs. Under the ISOS‐L‐3 testing protocol (maximum power point (MPP) tracking in an environment with relative humidity of ≈50% at ≈65 °C), the treated PSCs maintain 97% of their original power conversion efficieney (PCE) after 300 h of aging. In contrast, control devices exhibit almost complete degradation, primarily due to rapid thermal‐induced I2 volatilization. These results demonstrate a promising strategy to overcome critical stability challenges in PSCs, particularly in scenarios involving thermal effects.
Mercaptoethylammonium iodide (ESAI) is incorporated into perovskite as an additive to inhibit the oxidation of I−, which provides a dynamic mechanism for the continuous reduction of I2 under light and thermal stresses, facilitating the healing of iodine‐induced degradations. Under ISOS‐L‐3 conditions, the device with ESAI retained 97% of the original power conversion efficiency (PCE) after 300 h.
A stable solid electrolyte interphase (SEI) has been proven to be a key enabler to most advanced battery chemistries, where the reactivity between the electrolyte and the anode operating beyond the ...electrolyte stability limits must be kinetically suppressed by such SEIs. The graphite anode used in state-of-the-art Li-ion batteries presents the most representative SEI example. Because of similar operation potentials between graphite and silicon (Si), a similar passivation mechanism has been thought to apply on the Si anode when using the same carbonate-based electrolytes. In this work, we found that the chemical formation process of a proto-SEI on Si is closely entangled with incessant SEI decomposition, detachment, and reparation, which lead to continuous lithium consumption. Using a special galvanostatic protocol designed to observe the SEI formation prior to Si lithiation, we were able to deconvolute the electrochemical formation of such dynamic SEI from the morphology and mechanical complexities of Si and showed that a pristine Si anode could not be fully passivated in carbonate-based electrolytes.
Nonradiative recombination losses occurring at the interface pose a significant obstacle to achieve high-efficiency perovskite solar cells (PSCs), particularly in inverted PSCs. Passivating surface ...defects using molecules with different functional groups represents one of the key strategies for enhancing PSCs efficiency. However, a lack of insight into the passivation orientation of molecules on the surface is a challenge for rational molecular design. In this study, aminothiol hydrochlorides with different alkyl chains but identical electron-donating (-SH) and electron-withdrawing (-NH3+) groups were employed to investigate the interplay between molecular structure, orientation, and interaction on perovskite surface. The 2-Aminoethane-1-thiol hydrochloride with shorter alkyl chains exhibited a preference of parallel orientations, which facilitating stronger interactions with the surface defects through strong coordination and hydrogen bonding. The resultant perovskite films following defect passivation demonstrate reduced ion migration, inhibition of nonradiative recombination, and more n-type characteristics for efficient electron transfer. Consequently, an impressive power conversion efficiency of 25% was achieved, maintaining 95% of its initial efficiency after 500 hours of continuous maximum power point tracking.
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