High-quality Perovskite Films Research Articles

Dual-Functional Passivation Agent of Natural Dye Congo Red For Enhanced Carbon-Based Perovskite Solar Cells.

Carbon-based perovskite solar cells (C-PSCs) have acquired broad interest due to their superior stability and lower cost compared with metal-based perovskite solar cells (M-PSCs). However, the presence of perovskite defects greatly limits the power conversion efficiency (PCE) and long-term stability of C-PSCs. Herein, a natural dye Congo red molecule containing dual-functional groups of amino and sulfonic acids is first used as a surface passivation agent to treat the surface of perovskite films. High-quality perovskite films with reducing surface defect density and inhibiting nonradiative recombination are obtained. It is shown that the Congo red molecules not only effectively interact with the perovskite, enhancing the crystallization and enlarging the crystal size, but also demonstrate positive contribution for light harvesting in the visible range. The maximum PCE of 16.22% is achieved at the optimal concentration of 0.2 mg/mL Congo red, which is much higher than 13.57% for the control device. After 840 h of storage at 30-40% relative humidity at room temperature, the unencapsulated C-PSCs can still maintain a high initial performance of 87.21% compared with 43.26% for the control cells.

Ultra-low dark current and high sensitivity lead-free perovskite–like photodetector realized by anti-solvent optimization Cs3Bi2I9 amorphous film

Compared with lead halide perovskite, bismuth-based perovskite has lower toxicity and air stability, demonstrating enormous potential for application, among them, Cs3Bi2I9 materials has been researched as an alternative to lead-based perovskite for application of optoelectronic devices. It is crucial for the realization of high-performance photodetectors which need high-quality perovskite thin films. Here, we prepared a lead-free, all-inorganic, Cs3Bi2I9 perovskite-like amorphous films by spin coating method, and diethyl ether was added as an anti-solvent at different times of spin-coating. The results show that the homogeneous and dense Cs3Bi2I9 amorphous films can be obtained by adding anti-solvent at 14seconds. Furthermore, Cs3Bi2I9 perovskite-like UV photodetector achieved extremely low dark current around ~pA range, high sensitivity of 1.10×104 was fabricated. Our research shows that the preparation of Cs3Bi2I9 amorphous films by the simple antisolvent-assisted spin-coating method are very promising for optoelectronic device.

The Molecular Additive N-Acetyl-L-Phenylalanine Delays the Crystallization and Suppresses the Phase Impurity for Achieving Triple-Cation Perovskite Solar Cells with Efficiency Over 25.

The crystallization process plays an important role in the formation of high-quality perovskite film for achieving efficient perovskite solar cells (PSCs), especially in the formation of mixed-cation perovskite film, as there are normally more phase impurities than in pure CH(NH2)2PbI3 (FAPbI3) film. Herein, a molecular additive strategy, i.e., introducing non-planar molecule N-acetyl-L-phenylalanine (APO) into the lead iodide (PbI2) precursor solution, is proposed to modulate crystallization kinetics and inhibit the generation of phase impurities of metastable pretreated perovskite film. The delayed crystallization process promotes a sufficient reaction between organic salts solution and inorganic Pb-I framework, and perovskite phase decomposition is prevented by forming strong hydrogen bonds between ─NH and I, resulting in the formation of uniform film with large-size crystal grains and high-purity crystalline phase. Ultimately, the target PSC devices achieve an impressive power conversion efficiency (PCE) of 25.05%, which is among the highest values of triple-cation (FAMACs) PSCs. Meanwhile, PSC modules with 10.8 cm2 obtain a PCE of 20.35%. Furthermore, the unencapsulated PSCs retain 94% of the initial efficiency after 40 days of storage under ambient conditions with 20% RH and also yield superior operational stability under light soaking at maximum power point tracking (MPPT) in nitrogen (N2) atmosphere.

Slowing the crystallization speed to prepare high-efficiency flexible tin-based perovskite solar cells

In this study, five hydrochlorides are used as additives to slow the crystallization rate between SnI2 and AI (A+=MA+, FA+, Cs+) to prepare high-quality perovskite films. This study on film morphology, crystallization and non-radiative recombination demonstrates the effects of organic amine cations with different chain lengths on the quality of thin films. A flexible solar cell device with a lead-free perovskite film doped with PACl is also obtained achieving an efficiency of 5.52 %.

All-In-One Additive Enabled Efficient and Stable Narrow-Bandgap Perovskites for Monolithic All-Perovskite Tandem Solar Cells.

Hybrid tin-lead (Sn-Pb) perovskites have garnered increasing attention due to their crucial role in all-perovskite tandem cells for surpassing the efficiency limit of single-junction solar cells. However, the easy oxidation of Sn2+ and fast crystallization of Sn-based perovskite present significant challenges for achieving high-quality hybrid Sn-Pb perovskite films, thereby limiting the device's performance and stability. Herein, an all-in-one additive, 2-amino-3-mercaptopropanoic acid hydrochloride (AMPH) is proposed, which can function as a reducing agent to suppress the formation of Sn4+ throughout the film preparation. Furthermore, the strong binding between AMPH and Sn-based precursor significantly slows down the crystallization process, resulting in a high-quality film with enhanced crystallinity. The remaining AMPH and its oxidation products within the film contribute to improves oxidation resistance and a substantial reduction in defect density, specifically Sn vacancies. Benefiting from the multifunctionalities of AMPH, a power conversion efficiency (PCE) of 23.07% is achieved for single-junction narrow-bandgap perovskite solar cells. The best-performing monolithic all-perovskite tandem cell also exhibits a PCE of 28.73% (certified 27.83%), which is among the highest efficiency reported yet. The tandem devices can also retain over 85% of their initial efficiencies after 500 hours of continuous operation at the maximum power point under one-sun illumination.

Analysis on future development of solar cells focusing on materials and devices

In recent times, solar cells have garnered significant attention due to their numerous advantages. These include continuously improving energy conversion efficiency, a simple solution preparation method, flexibility, lightweight design, wearability, suitability for ultra-lightweight space applications, and low-cost material components. Perovskite solar cells have achieved impressive efficiencies of over 25% by using high-quality perovskite films synthesized at low temperatures and by making advancements in compatible interface and electrode materials. Moreover, the stability of cells has become a major focus of research. This paper analyzes the development history, material system, device structure, challenges, and future development direction of perovskite solar cells. The unique photoelectric properties and tunable band gap of materials have made them a hot topic in the field of solar cells. In this paper, the basic characteristics and synthesis methods of perovskite materials are introduced before discussing the device structure, interface engineering, and stability of perovskite solar cells in detail. Finally, it prospects on the future development trend of perovskite solar cells.

Preparation of efficient and stable FA0.75MA0.25SnI3 perovskite solar cells using passivation materials with multiple F hydrophobic group

Although Sn-based perovskite solar cells (PSC) have impressive conversion efficiency, their stability needs to be improved. Herein, 3,4,5-trifluorophenol (C6H3F3O) containing –F and –OH groups was introduced to improve the film stability and quality of FA0.75MA0.25SnI3. –F groups with low surface energy cause C6H3F3O to spontaneously migrate to the air-solution interface and attract the SnI64− octahedron to the solution-air surface through hydrogen bond interactions between –OH and I. This leads to preferential nucleation of dense, high-quality perovskite films at the solution-air surface and orderly growth from top to bottom. Additionally, C6H3F3O is bonded to the surface of the film, and the outward-facing hydrophobic –F groups effectively shield FA0.75MA0.25SnI3 from water infiltration. The C6H3F3O-doped PSC exhibited a champion efficiency of 10.47 % and long-term stability of over 1000 h, retaining 80 % of its initial efficiency (in N2).

High-Quality Thiophene-Based Two-Dimensional Perovskite Films Prepared with Dual Additives and Their Application in Solar Cells.

This study explores the optimization of (TMA)2MA4Pb5I16 perovskite films by regulating the film quality through the addition of MACl and MAAc additives. We found that adding MACl resulted in a film of larger grains with a power conversion efficiency (PCE) of 5.34%, while excessive MACl led to the formation of low-dimensional phases. Adding 7.5% MAAc improved the film quality with a PCE of 5.64%, although excessive MAAc induces pores and smaller grains. To address these issues, we proposed the combined use of MACl and MAAc additives, resulting in films with a larger grain size, smoother surface, and denser structure. Remarkably, the addition of MAAc + MACl achieved a champion PCE of 8.86% with good reproducibility. Mechanism studies revealed that TMA and MAAc formed a stable complex with PbI2 in solution, disrupting nucleation laws and promoting the formation of nuclei, leading to denser films with smaller grains. Additionally, the MACl treatment effectively promoted grain growth, resulting in high-quality films. This study presents novel insights into dual additive usage and their role in film crystallization, offering valuable guidance for the preparation of high-performance perovskite films.

Enhancing the emissive film quality: A new role of TADF materials for high-performance blue perovskite light-emitting diodes

Thermally activated delayed fluorescence (TADF) materials are widely used in the field of organic light-emitting diodes (OLEDs) because they can capture both singlet and triplet excitons for light emission. However, only scare attention has been paid to the application of TADF materials in perovskite LEDs (PeLEDs) and the understanding of effects of TADF materials in PeLEDs is limited. In this study, a new role of TADF materials for achieving high-quality perovskite films to enhance the performance of PeLEDs is emphasized. TADF materials are introduced into quasi-2D blue PeLEDs to assist in the crystallization of perovskites during film annealing and ensure the formation of high-quality films with reduced defects, enhancing device performance. Additionally, a step-like hole transport layer has been constructed to reduce the hole transport barrier, which can further enhance the performance of PeLEDs. The resultant blue PeLEDs exhibits an external quantum efficiency of 5.44 %, which is 12.7-fold higher than that of the control device. Furthermore, a turn-on voltage of 2.6 V is achieved, which is the lowest for TADF-based blue PeLEDs. The findings may not only unlock a new role of TADF materials in blue PeLEDs, but also provide an alternative pathway to achieve high-performance PeLEDs.

Performance enhancement of inverted CsPbI2Br perovskite solar cells via butylammonium cation additive modification

Defects in all inorganic perovskite films currently limit the efficiency and long-term stability of perovskite solar cells (PSCs). In this study, we utilized the n-butylammonium cation as an additive to enhance the performance of PSCs. By incorporating n-butylammonium iodide, modifications in crystallization were achieved, resulting in high-quality CsPbI2Br perovskite films with larger grain sizes. As a result, the inverted PSCs with 1 mol percent additive exhibited an enhanced power conversion efficiency (PCE) of up to 13.0%, compared to the control PCE of 10.8%. The improvement can be primarily attributed to reduced trap states and suppressed charge recombination within the inverted PSCs. Furthermore, the hydrophobic nature of the additive noticeably improved the long-term stability of CsPbI2Br PSCs.

Functional design and understanding of effective additives for achieving high-quality perovskite films and passivating surface defects

Achieving high-quality perovskite films without surface defects is regarded as a crucial target for the development of durable high-performance perovskite solar cells. Additive engineering is commonly employed to simultaneously control the growth of perovskite crystals and passivate defects. Here, 4-(trifluoromethyl)benzoic anhydride (4-TBA) composed of benzene rings functionalized with carbonyl and trifluoromethyl groups was used as an example additive to study the characteristics of additives used for producing high-quality perovskites and controlling their surface properties. The interaction between 4-TBA and perovskite precursor materials was investigated using density functional theory (DFT) simulations. The electron-rich carbonyl group efficiently passivated the under-coordinated lead-ion defects. Additionally, hydrogen bonding between trifluoromethyl and organic cations prevents the generation of cation vacancies. Because of its intrinsic hydrophobicity, the trifluoromethyl group simultaneously improves the moisture and heat stability of the film. 4-TBA serves as a universal modifier for various perovskite compositions. The power conversion efficiency (PCE) of inverted perovskite solar cells (PSCs) based on methylammonium (MA) with 4-TBA was improved from 16.15% to 19.28%. Similarly, the PCE of inverted PSCs based on a cesium formamidinium MA (CsFAMA) perovskite film increased from 20.72% to 23.58%, upon addition of 4-TBA. Furthermore, the moisture and thermal stability of 4-TBA-treated films and devices was significantly enhanced, along with prolonged device performance. Our work provides guidance on selecting the structure and functional groups that are essential for surface defect passivation and the production of high-quality perovskites.

Low-temperature crosslinked hole transport material for high-performance inverted perovskite solar cells

Hole transport materials (HTMs) play a crucial role in the development of high-performance inverted perovskite solar cells (PSCs) by facilitating hole transport, passivating defects, and tuning crystallization. Achieving high efficiency and stability remains a key challenge for the PSCs. Crosslinked HTMs combine the efficiency of small molecules with enhanced environmental stability, however, a significant challenge in developing crosslinked HTMs for PSCs is the high temperature required for crosslinking. In this work, we synthesized a concise crosslinkable HTM, Tetrastyrenebiphenyldiamine (TPDA), based on a biphenyl core with four styrene groups, using a one-step method. TPDA can be crosslinked through an annealing process at 100℃ for 10 min without the need for any dopants or initiators. Interestingly, the compact films formed in the anneal process and the excellent spreadability for the perovskite precursor solution leading to the high-quality perovskite films, as a result, the inverted devices based on CL-TPDA achieve a champion power conversion efficiency (PCE) of 21.4%. Furthermore, the stability of the devices without encapsulation has notably improved. The PCE maintains over 85% of its initial value after 1000 h of storage in ambient air (25℃, relative humidity about 50%).

Enhanced the efficiency of carbon based perovskite solar cells via g-C3N4 as functional additives

The quality of perovskite layer plays an important role in the performance of perovskite solar cells. Various defects can arise during the crystal growth process of Perovskite thin film. However, by using additives. It is possible to effectively enhance crystallize and form high-quality perovskite films with improved morphology. g-C3N4, a carbon–nitrogen ring with delocalized π electrons and certain conductivity, facilitates the transport of charge carriers. When it is utilized as an additive in perovskite solar cells, g-C3N4 not only improves the quality and crystallinity of perovskite films, but also passivates defects. As a result of these improvements, the optimal efficiency for preparing carbon-based perovskite solar cells is 13.74 %. This represents a significant increase in photoelectric conversion efficiency from 10.39 % to 13.74 %, corresponding to a remarkable enhancement of 32.24 %. These findings provide valuable insights into the potential application of two-dimensional materials and carbon nitrogen ring for enhancing the performance of perovskite solar cells.

Studying the effect of ambient temperature variations on perovskite precursor film formation using different antisolvents

This study investigates the sensitivity of two antisolvents to ambient temperature fluctuations during the fabrication of triple-cation perovskite thin films. Chlorobenzene (CB) and ethyl acetate (EA) were employed as antisolvents in the preparation of perovskite solar cells (PSCs) under identical ambient temperature variation conditions. The experimental results reveal that the quality of the perovskite films does not exhibit a consistent trend in response to ambient temperature changes depending on the antisolvent used. When CB was used as the antisolvent, the highest-performing device, produced at an ambient temperature of 18 °C, achieved a power conversion efficiency (PCE) of 19.9 %. In contrast, when EA was employed as the antisolvent, the highest-performing device was fabricated at 25 °C, reaching a PCE of 20.5 %. Furthermore, when the ambient temperature exceeded 30 °C, all films prepared with either antisolvent exhibited significant cracking, indicating that elevated temperatures adversely affect perovskite film formation. To further investigate the mechanism through which ambient temperature affects the film-forming process, antisolvents at varying temperatures were used during perovskite film preparation to simulate transient temperature increases during formation. This study reveals that the impact of ambient temperature variations on perovskite film formation does not exhibit a uniform trend but is significantly influenced by the choice of antisolvent. Moreover, this work offers valuable insights for optimizing the fabrication of high-quality perovskite thin films.

Regulation of Wide Bandgap Perovskite by Rubidium Thiocyanate for Efficient Silicon/Perovskite Tandem Solar Cells.

Developing high-quality wide bandgap (WBG) perovskites with ≈1.7eV bandgap (Eg) is critical to couple with silicon and create efficient silicon/perovskite tandem devices. The sufferings of large open-circuit voltage (VOC) loss and unstable power output under operation continuously highlight the criticality to fully develop high-quality WBG perovskite films. In this study, rubidium and thiocyanate as additive regulators in WBG perovskites are incorporated, significantly reducing non-radiative recombination, ion-migration, and phase segregation. The optimized 1.66 eV Eg perovskite solar cells achieved state-of-art 1.3V VOC (0.36V deficit), and delivered a stabilized power conversion efficiency of 24.3%, along with good device stability (20% degradation (T80) after over 994h of operation under 1 sun at ≈65°C). When integrated with a flat front side silicon cell, silicon/perovskite two-terminal tandem device (30% efficient) is obtained with a 1.97V VOC, and T90 operational lifetime of more than 600h at room temperature.

Innovative Approaches to Large-Area Perovskite Solar Cell Fabrication Using Slit Coating.

Perovskite solar cells (PSCs) are gaining prominence in the photovoltaic industry due to their exceptional photoelectric performance and low manufacturing costs, achieving a significant power conversion efficiency of 26.4%, which closely rivals that of silicon solar cells. Despite substantial advancements, the effective area of high-efficiency PSCs is typically limited to about 0.1 cm2 in laboratory settings, with efficiency decreasing as the area increases. The limitation poses a major obstacle to commercialization, as large-area, high-quality perovskite films are crucial for commercial applications. This paper reviews current techniques for producing large-area perovskites, focusing on slot-die coating, a method that has attracted attention for its revolutionary potential in PSC manufacturing. Slot-die coating allows for precise control over film thickness and is compatible with roll-to-roll systems, making it suitable for large-scale applications. The paper systematically outlines the characteristics of slot-die coating, along with its advantages and disadvantages in commercial applications, suggests corresponding optimization strategies, and discusses future development directions to enhance the scalability and efficiency of PSCs, paving the way for broader commercial deployment.

Synergistic Modulation of Sn2+ Oxidation and Perovskite Crystallization Induced by 4-Hydroxypyridine for Stable Lead-Free Solar Cells.

Tin perovskites present promising alternatives to lead perovskites, offering comparable optoelectronic properties alongside environmentally friendly characteristics. However, the rapid crystallization and easy oxidation of Sn2+ lead to poor film quality, further constraining the device performance. Here, 4-hydroxypyridine (4-HP) is introduced into the tin perovskite precursor for fabrication of high-quality tin perovskite films. 4-HP could modulate the colloidal size of prenucleation perovskite clusters in the precursor, thus inducing fast nucleation and retarding the crystal growth rate of tin perovskite through the formation of chemical interaction between nitrogen of pyridine and Sn2+ ions. Furthermore, the hydroxyl group on the pyridine ring contributes to suppressing the oxidation of Sn2+. As a result, the power conversion efficiency (PCE) of the devices based on 4-HP increases up to 11.3%. The stability of the unencapsulated devices shows significant improvement, retaining 100% of their initial PCEs after 2000 h of storage in N2 with 50-100 ppm of O2. This research presents a novel approach to the synchronized regulation of tin perovskite crystallization and the suppression of Sn2+ oxidation.

The role of SiO2 buffer layer in the molecular beam epitaxy growth of CsPbBr3 perovskite on Si(111)

Here we present the growth of molecular beam epitaxy (MBE) CsPbBr3 perovskite films in the orthorhombic crystal structure, with unique structural and morphological properties. CsPbBr3 MBE perovskite films, with thickness ranging from a few nm to 300 nm, were grown in ultra-high vacuum on a Si(111)7 × 7 reconstructed surface, and after the formation of about 2 nm of SiO2, obtained exposing the clean reconstructed Si surface to molecular oxygen that serves to decouple the film from substrate. X-ray diffraction, and electron microscopies, such as scanning electron microscopy and high-angle annular dark-field scanning transmission electron microscopy measurements showed remarkable structural, as well as morphological features, indicating extremely high crystallinity over a large area and across the bulk of the perovskite film. Through the X-ray diffraction patterns we found very narrow (002) and (110) reflections of CsPbBr3 in pure orthorhombic phase, exhibiting a full width at half maximum of only 0.035°, value similar to a bulk Si single crystals, and a surface morphology composed of flat areas up to micrometres in lateral size. Our results shed new light both on preparation of high crystal quality perovskite films, and on the intrinsic properties of this striking fully-inorganic materials, which are exploitable for potential applications in electronic/optoelectronic devices and next generation photovoltaic solar cells.

Enhanced Homogeneity in Perovskite Photovoltaic Films via Antisolvent Extraction of a Methylamine-Based Gel Precursor.

Solution-processed perovskite solar cells (PSCs) are at the forefront of next-generation photovoltaics, exhibiting outstanding photoelectric performance and cost-effective manufacturing. However, the prevalent use of polar aprotic solvents such as N,N-dimethylformamide and dimethyl sulfoxide in the preparation of perovskite precursor solution hinders complete solvent removal during film formation. Their high boiling points and strong coordinating abilities lead to solvated intermediates and heterogeneous perovskite crystal nucleation, particularly in the absence of the antisolvent-assisted crystallization. To address this, we developed a methylamine (MA)-based gel dispersion system that significantly improves the uniformity of perovskite films. By employing ethyl acetate (EA) antisolvent extraction, the gel precursor is extracted from a solution of MAI and PbI2 in MA ethanol, which is then diluted in pure acetonitrile (ACN) solvent to form a clear perovskite precursor solution. Benefiting from the highly volatile nature of the ACN-based gel perovskite precursor solution and its rich concentration of high-valent PbIn2-n coordination compounds, this approach enables the fabrication of high-quality MAPbI3 perovskite films, yielding PCEs of 21.34% for PSC and 19.77% for a 5 × 5 cm2 mini-module. This MA-based gel perovskite precursor strategy offers a promising avenue for potential applications in the scalable manufacture of PSCs.

Combining SSVD and subsequent heat treatment processes to fabricate high-quality CsPbBr3 perovskite films

Perovskites, known for their excellent photoluminescence efficiency and color purity, have seen widespread application in flat panel displays and lighting in recent years. Here, we present a process for fabricating CsPbBr3 perovskite film (PeFilm) with high luminescent properties and remarkable weather resistance. By combining single-source vapor deposition (SSVD) with subsequent heat treatment, the quality of PeFilms has been significantly improved. We enhanced the quality of PeFilms by using a thermal annealing process to remove PbBr2 from CsPb2Br5. During annealing, PbBr2 evaporates from PeFilms, changing the crystal phase to CsPbBr3. The heat treatment rearranges atoms between grains, promoting grain growth and fusion, producing larger crystals and reducing defects. The research results demonstrate that the integration of SSVD and appropriate heat treatment enables the fabrication of the CsPbBr3 PeFilm with an emission wavelength of 533 nm, CIE coordinates of (0.1842, 0.7797), and a photoluminescence quantum yield (PLQY) of 52.1%, and even after storing it in atmospheric conditions for 100 days, the PLQY of the CsPbBr3 PeFilm remains above 52%, demonstrating excellent stability.