Inverted Perovskite Solar Cells Research Articles

Asymmetric Modification of Carbazole Based Self-Assembled Monolayers by Hybrid Strategy for Inverted Perovskite Solar Cells.

Carbazole-based self-assembled molecules (SAMs) are widely applied in inverted perovskite solar cells (iPSCs) due to their unique molecular properties. However, the symmetrical structure of the carbazole-based SAMs makes it difficult to finely regulate their performance, which impedes the further enhancement of the efficiency and stability of iPSCs. This work shows that by building an asymmetric carbazole core, the crucial properties of SAM molecules can be effectively regulated. It has been confirmed that the hybrid thieno[2,3-b]thiophene unit of this asymmetric core governs the energy level, the surface wettability, and the defect passivation capability of the SAMs, while the substituent of core has a greater impact on the molecular dipole and device stability. The synergistic effects from thieno[2,3-b]thiophene and fluorine lead to the KF-derived iPSC demonstrating a certified power conversion efficiency (PCE) of 25.17% and excellent operational stability. This hybrid design concept offers a promising approach for the further structural modification of SAMs in iPSCs.

Asymmetric Modification of Carbazole Based Self‐Assembled Monolayers by Hybrid Strategy for Inverted Perovskite Solar Cells

Asymmetric Modification of Carbazole Based Self‐Assembled Monolayers by Hybrid Strategy for Inverted Perovskite Solar Cells

A Surface-Reconstructed Bilayer Heterojunction Enables Efficient and Stable Inverted Perovskite Solar Cells.

The efficiency of perovskite photovoltaics remains distant from their theoretical limits, primarily due to high photovoltage losses. Here a strategy is reported to minimize voltage losses by reconstructing the perovskite surface into a bilayer heterojunction (BLH) structure. Unlike conventional low-dimensional capping layers, typically constrained to a few nanometers to prevent low fill factors, this methodology facilitates a more comprehensive reaction with surface defects, allowing a more substantial capping layer (≈50 nanometers) without compromising charge transport integrity. Time-resolved microwave conductivity analysis indicates a significant reduction in trap density at the top region of the perovskite film, showing an order of magnitude lower than that of the pristine sample. Incorporating this BLH in inverted cells results in a remarkably low photovoltage deficit of 325mV, leading to a power conversion efficiency (PCE) of 26.1% (25.72% certified). The encapsulated device maintains 94% of its original efficiency after 1200h of maximum power point tracking under one sun illumination at 65°C.

Molecularly tailored bifunctional nano-overlayers for efficient and stable inverted perovskite solar cells

Triple cation perovskite solar cells (PSCs) have made remarkable progress in power conversion efficiency (PCE), which is also related to the interface regulation layers between the active layer and electron transport layer (ETL). The ionic nature of the perovskite lattice has enabled approaches to passivate molecular defects through the interaction of functional groups. Herein, a passivator OXD-7 is introduced as a modified layer to passivate surface defects and accelerate electron transfer. It has been observed that OXD-7 can alleviate the micro-strain of the perovskite thin films through intermolecular bonding, which suppresses the iodide vacancy on the perovskite surface. Additionally, the OXD-7 reduces the surface energy of the perovskite films and inhibits the formation of δ-FAPbI3 on the surface of perovskite film. Consequently, the resulting devices demonstrate improved fill factor and device stability. Under optimal fabrication conditions, triple cation mixed perovskite solar cells with an inverted structure achieve a PCE of 23.83%.

Substrate Induced p-n Transition for Inverted Perovskite Solar Cells.

The p- or n-type property of semiconductor materials directly determine the final performance of photoelectronic devices. Generally, perovskite deposited on p-type substrate tends to be p-type, while perovskite deposited on n-type substrate tends to be n-type. Motived by this, a substrate-induced re-growth strategy is reported to induce p- to n-transition of perovskite surface in inverted perovskite solar cells (PSCs). p-type perovskite film is obtained and crystallized on p-type substrate first. Then an n-type ITO/SnO2 substrate with saturated perovskite solution is pressed onto the perovskite film and annealed to induce the secondary re-growth of perovskite surface region. As a result, p- to n-type transition happens and induces an extra junction at perovskite surface region, thus enhancing the built-in potential and promoting carrier extraction in PSCs. Resulting inverted PSCs exhibit high efficiency of over 25% with good operational stability, retaining 90% of initial efficiency after maximum power point (MPP) tracking for 800h at 65°C with ISOS-L-2 protocol.

Lead Iodide Redistribution Enables In Situ Passivation for Blading Inverted Perovskite Solar Cells with 24.5% Efficiency.

Blade-coating stands out as an alternative for fabricating scalable perovskite solar cells. However, it demands special control of the precursor composition regarding nucleation and crystallization and currently exhibits lower performance than the spin-coating process. It is mainly the resulting film morphology and excess lead iodide (PbI2) distribution that influences the optoelectronic properties. Here, the effectiveness of introducing N-Methyl-2-pyrrolidone (NMP) to regulate the structure of the perovskite layer and the redistribution of PbI2 is found. The introduction of NMP leads to the accumulation of excess PbI2, mainly on the top surface, reducing residual PbI2 at the perovskite buried interface. This not only facilitates the passivation of perovskite grain boundaries but also eliminates the potential degradation of the PbI2 triggered by light illumination in the perovskite buried interface. The optimized NMP-modified inverted perovskite solar cell achieves a champion efficiency of 24.5%, among the highest reported blade-coated perovskite solar cells. Furthermore, 13.68cm2 blading perovskite solar modules are fabricated and demonstrate an efficiency of up to 20.4%. These findings underscore that with proper modulation of precursor composition, blade-coating can be a feasible and superior alternative for manufacturing high-quality perovskite films, paving the way for their large-scale applications in photovoltaic technology.

Uniform Molecular Adsorption Energy‐Driven Homogeneous Crystallization and Dual‐Interface Modification for High Efficiency and Thermal Stability in Inverted Perovskite Solar Cells (Adv. Funct. Mater. 44/2024)

Uniform Molecular Adsorption Energy‐Driven Homogeneous Crystallization and Dual‐Interface Modification for High Efficiency and Thermal Stability in Inverted Perovskite Solar Cells (Adv. Funct. Mater. 44/2024)

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.

Improved efficiency and stability of inverse perovskite solar cells via passivation cleaning

Amidst the global energy and environmental crisis, the quest for efficient solar energy utilization intensifies. Perovskite solar cells, with efficiencies over 26% and cost-effective production, are at the forefront of research. Yet, their stability remains a barrier to industrial application. This study introduces innovative strategies to enhance the stability of inverted perovskite solar cells. By bulk and surface passivation, defect density is reduced, followed by a "passivation cleaning" using Apacl amino acid salt and isopropyl alcohol to refine film surface quality. Employing X-ray diffraction (XRD), scanning electron microscope (SEM), and atomic force microscopy (AFM), we confirmed that this process effectively neutralizes surface defects and curbs non-radiative recombination, achieving 22.6% efficiency for perovskite solar cells with the composition Cs0.15FA0.85PbI3. Crucially, the stability of treated cells in long-term tests has been markedly enhanced, laying groundwork for industrial viability.

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%).

Surface Lattice Engineering Enables Efficient Inverted Perovskite Solar Cells

AbstractState‐of‐the‐art inverted perovskite solar cells (PSCs) have exhibited considerable promise for commercialization due to their prospective stability. However, the intricate crystallization of halide perovskite, especially for multi‐component perovskites, not only distorts the surface lattice from its ideal form but also introduces numerous unsaturated dangling bonds to form surface defects, which can easily lead to reduced stability and poor performance. Herein, a surface lattice engineering is developed by coupling surface unsaturated ions and regulating ion bonding lengths/angles to achieve efficient and stable inverted PSCs. The renovated surface lattice not only eliminates shallow/deep level defects on the surface of perovskite, but also enhances photo/thermal stability of the materials. Moreover, the surface lattice engineering contributes to uniform potential surface, and improves energy‐level alignment at the interfaces of the perovskite and C60 carrier transport layer, enhancing charge carrier extraction and transportation. Finally, the champion PSC delivers an impressive efficiency of 25.82% (certified 25.5%). Moreover, these PSCs exhibit excellent operational stability, retaining 94% initial efficiency after more than ≈1 000h maximum power point test.

Functionalized sp2 Carbon-Conjugated Covalent Organic Frameworks for Interfacial Modulation of Inverted Perovskite Solar Cells.

Interfacial modulation utilizing functional materials is proven to be crucial for obtaining high photovoltaic performance in lead halide perovskite solar cells (PSCs). This study investigates, for the first time, the utilization of a pyrene-based sp2 carbon-conjugated covalent organic framework (sp2c-COF) as an interfacial layer in inverted PSCs. Functionalized with cyano (-CN) Lewis base groups, the sp2c-COF exhibits a dual effect, simultaneously passivating both the NiOx and the perovskite layers. Detailed characterization results highlight the role of sp2c-COF in reducing the Ni3+ defect density in NiOx films and forming Lewis acid-base adducts with undercoordinated Pb2+ on the perovskite surfaces, thereby inhibiting interfacial redox reactions and suppressing non-radiative recombination. Moreover, sp2c-COF leads to improved crystallinity of perovskite films. Benefiting from the synergistic effects, sp2c-COF-modified devices delivered a champion efficiency of 17.64%. These findings underscore the potential of sp2c-COF as a functional interface material for PSCs, offering enhanced efficiency and stability. The study contributes to advancing the understanding and application of covalent organic frameworks in photovoltaic technologies.

Dipropyl sulfide optimized buried interface to improve the performance of inverted perovskite solar cells

Recently, [4–(3,6-dimethyl-9H-carbazol-9-yl)butyl] phosphonic acid (Me-4PACz) has garnered significant attention as a highly effective passivation layer for NiOx. However, the Me-4PACz passivation layer shows low wettability to perovskite precursors, hindering the crystallization of perovskite. Moreover, Me-4PACz does not uniformly and completely cover NiOx, failing to achieve an optimal passivation effect. The presence of high-valence-state Ni species and reactive hydroxyls on the NiOx film surface leads to perovskite degradation. To address this, dipropyl sulfide (DPS) was incorporated into a solution of Me-4PACz. This approach not only enhances the wettability of Me-4PACz, facilitating the growth of larger perovskite grains but also enables Me-4PACz to form a homogeneous passivation layer with strong coverage. This effectively prevents direct contact between NiOx and perovskite films. Additionally, DPS interacts with reactive hydroxyls, removing them from the NiOx surface and mitigating the deprotonation reaction of MA/FA in perovskite. Furthermore, DPS is reducible, which helps in reducing high-valent Ni (Ni4+), thereby decreasing redox reactions at the interface. As a result, the optimized perovskite solar cells with DPS achieved a power conversion efficiency (PCE) of 22.29%, higher than the control device of 20.52%. Moreover, the DPS-decorated device demonstrated excellent stability, retaining over 80% of its initial PCE value, compared to only 60% retention in the control device. This work modified the buried interface and offers valuable insights for subsequent similar studies.

Surface Property Regulation of a Magnetron-Sputtered NiOx Hole Transport Layer for High-Performance Inverted Perovskite Solar Cells.

The inverted perovskite solar cells (PSCs) are gaining increasing attention recently for their unprecedented advantages, such as better integration with tandem and flexible designs, negligible hysteresis, good operational stability, and compatibility with commercially scalable fabrication approaches. Nickel oxide (NiOx) films prepared by magnetron sputtering technology exhibit excellent scalability and reproducibility, which could well meet the requirements of the large-scale production of inverted PSCs. However, NiOx prepared by vacuum methods generally has fewer surface hydroxyl groups, deteriorating the wettability and damaging the interface contact with the perovskite. Particularly, the Ni3+ defects on the NiOx surface could lead to unfavorable redox reactions with organic cations in the perovskite under high temperatures, promoting the rapid degradation of the perovskite. Thus, surface regulation of sputtered NiOx is imperative for high-performance PSCs. Herein, 4-(trifluoromethyl) phenylcarbamate hydrochloride (TFFA) was used to regulate the surface properties of sputtered NiOx. The strongly electronegative F ions in TFFA passivated the Ni3+ defects on the NiOx surface, suppressed unfavorable interface reactions, and improved charge recombination. The polar ammonium functional group was used to adjust the surface energy of NiOx, thereby improving the wettability and optimizing the crystallization kinetics of the perovskite. As a result, the power conversion efficiency (PCE) of PSCs reached 22.76%, which was among the highest PCEs reported for sputtered NiOx-based inverted PSCs to date. Moreover, the unencapsulated target devices exhibited better stability, maintaining over 85% of the initial PCE after aging for approximately 1200 h in a N2 environment. Our achievements pointed out a practical strategy for enhancing the performance of sputtered NiOx-based inverted PSCs, which could potentially accelerate the development and application of large-area PSCs.

Lead carbanion anchoring for surface passivation to boost efficiency of inverted perovskite solar cells to over 25%

In this study, we synthesize lead carbanion complex to act as interface passivator for inverted perovskite solar cells. The strong Pb–C− bond between carbanion and lead-rich perovskite surface can stabilize the underlying perovskite to reduce defects and hence enhance photovoltaic performance. The carrier transfer behavior as a function of the lead carbanion complex was measured to optimize device performance by surface passivation. The devices achieved a power conversion efficiency of 25.16 % with a high open-circuit voltage of 1.17 V and a minimal voltage loss of 0.38 V. The perovskite solar cells with carbanion passivation maintained high performance over 600 h and had a lifespan in air exceeding 90 days without encapsulation. Our work introduces a new class of carbanion passivators to simultaneously improve the efficiency and stability of perovskite solar cells.

Covalent Organic Framework-Incorporated MAPbI3 for Inverted Perovskite Solar Cells with Enhanced Efficiency and Stability

Covalent Organic Framework-Incorporated MAPbI₃ for Inverted Perovskite Solar Cells with Enhanced Efficiency and Stability

Regulating phase homogeneity by self-assembled molecules for enhanced efficiency and stability of inverted perovskite solar cells

Regulating phase homogeneity by self-assembled molecules for enhanced efficiency and stability of inverted perovskite solar cells

Spin‐Coated and Vacuum‐Processed Hole‐Extracting Self‐Assembled Multilayers with H‐Aggregation for High‐Performance Inverted Perovskite Solar Cells

AbstractWe report a highly crystalline self‐assembled multilayer (SAMUL) that is fundamentally different from the conventional monolayer or disordered bilayer used for hole‐extraction in inverted perovskite solar cells (PSCs). The SAMUL can be easily formed on ITO substrate to establish better surface coverage to enhance the performance and stability of PSCs. A detailed structure‐property‐performance relationship of molecules used for SAMUL is established through a systematic study of their crystallinity, molecular packing, and hole‐transporting properties. These SAMULs are rationally optimized by varying their molecular structures and deposition methods through thermal evaporation or spin‐coating for fabricating PSCs. The CbzNaphPPA‐based SAMUL was chosen for fabricating inverted PSCs due to it exhibiting the highest crystallinity and hole mobility which is derived from the ordered H‐aggregation. This resulted in a remarkably high fill factor of 86.45 %, which enables a very impressive power conversion efficiency (PCE) of 26.07 % to be achieved along with excellent device stability (94 % of its initial PCE retained after continuous operation for 1200 h under 1‐sun irradiation at maximum power point at 65 °C). Additionally, a record‐high PCE of 23.50 % could be achieved by adopting a thermally evaporated SAMUL. This greatly simplifies and broadens the scope for SAM to be used for large‐area devices on diverse substrates.

Spin-Coated and Vacuum-Processed Hole-Extracting Self-Assembled Multilayers with H-Aggregation for High-Performance Inverted Perovskite Solar Cells.

We report a highly crystalline self-assembled multilayer (SAMUL) that is fundamentally different from the conventional monolayer or disordered bilayer used for hole-extraction in inverted perovskite solar cells (PSCs). The SAMUL can be easily formed on ITO substrate to establish better surface coverage to enhance the performance and stability of PSCs. A detailed structure-property-performance relationship of molecules used for SAMUL is established through a systematic study of their crystallinity, molecular packing, and hole-transporting properties. These SAMULs are rationally optimized by varying their molecular structures and deposition methods through thermal evaporation or spin-coating for fabricating PSCs. The CbzNaphPPA-based SAMUL was chosen for fabricating inverted PSCs due to it exhibiting the highest crystallinity and hole mobility which is derived from the ordered H-aggregation. This resulted in a remarkably high fill factor of 86.45 %, which enables a very impressive power conversion efficiency (PCE) of 26.07 % to be achieved along with excellent device stability (94 % of its initial PCE retained after continuous operation for 1200 h under 1-sun irradiation at maximum power point at 65 °C). Additionally, a record-high PCE of 23.50 % could be achieved by adopting a thermally evaporated SAMUL. This greatly simplifies and broadens the scope for SAM to be used for large-area devices on diverse substrates.

Enhanced Buried Interface Engineering for Efficient Inverted Perovskite Solar Cells Fabricated via Vapor-Solid Reaction.

Vapor-deposited inverted perovskite solar cells utilizing self-assembled monolayer (SAM) as hole transport material have gained significant attention for their high efficiencies and compatibility with silicon/perovskite monolithic tandem devices. However, as a small molecule, the SAM layer suffers low thermal tolerance in comparison with other metal oxide or polymers, rendering poor efficiency in solar device with high-temperature (> 160°C) fabricating procedures. In this study, a dual modification approach involving AlOx and F-doped phenyltrimethylammonium bromide (F-PTABr) layers is introduced to enhance the buried interface. The AlOx dielectric layer improves the interface contact and prevents the upward diffusion of SAM molecules during the vapor-solid reaction at 170°C, while the F-PTABr layer regulates crystal growth and reduces the interfacial defects. As a result, the AlOx/F-PTABr-treated perovskite film exhibits a homogeneous, pinhole-free morphology with improved crystal quality compared to the control films. This leads to a champion power conversion efficiency of 21.53% for the inverted perovskite solar cells. Moreover, the encapsulated devices maintained 90% of the initial efficiency after 600h of ageing at 85°C in air, demonstrating promising potential for silicon/perovskite tandem application.