Chen Weijie

A one-stone-for-multiple-birds additive strategy based on lanthanide trifluoromethanesulfonates is presented to obtain highly efficient and stable carbon-based hole-transport-layer-free CsPbI₂Br solar cells, and achieve a power conversion efficiency of up to 15.13% with notably enhanced long-term stability and reduced current-voltage hysteresis.

Abstract

During fabrication and operation of perovskite solar cells (PSCs), defects commonly arise within the crystals as well as at grain boundaries. However, conventional additive strategies typically only serve to mitigate the occurrence of a single defect and fail to significantly enhance device performance. Herein, carbon-based hole-transport-layer-free CsPbI₂Br devices are focused on, one kind of important PSCs with more stable structure and an appropriate bandgap for a semitransparent solar cell or a top cell in a tandem configuration, and present a highly efficient one-stone-for-multiple-birds additive strategy based on lanthanide trifluoromethanesulfonates (Ln(OTF)₃, Ln: neodymium (Nd), europium (Eu), dysprosium (Dy), thulium (Tm)). Density functional theory calculations reveal that the Ln³⁺ ions with a smaller radius can elevate defect formation energy for Pb and I vacancies within the crystals, while the presence of OTF⁻ can effectively passivating uncoordinated Pb²⁺ at grain boundaries. In addition, Ln(OTF)₃ addition increases the grain size and meanwhile reduces the surface roughness of the CsPbI₂Br layers. All these positive contributions lead to a significant enhancement in power conversion efficiency (PCE) to 15.13% which is among the top PCEs reported for the corresponding solar cells, from 11.80% of the pristine device without Tm(OTF)₃ addition, while notably boosting long-term stability and reducing current–voltage hysteresis.

The addition of g-C₃N₅ not only improves the charge mobility and hole carrier concentration of PM6, but also effectively enhances the crystallization of active layer, thereby rising the efficiency and stability of organic solar cells OSCs.

Abstract

Molecular doping of organic semiconductor is a great strategy for significantly regulating the electronic band structure of organic semiconductor while increasing charge mobility and carrier concentration. Here, a facile strategy is presented by introducing 2D g-C₃N₅ as a p-dopant into PM6, improving the charge mobility and hole carrier concentration of PM6. Moreover, the electron transfer between PM6 and g-C₃N₅ can effectively downshift the Fermi energy level and highest occupied molecular orbital (HOMO) energy level of PM6, which leads to the increase the built-in electric field of organic solar cells (OSCs). The addition of g-C₃N₅ also effectively enhances the crystallization of active layer, thereby improving the stability of OSCs. As a result, a champion bulk-heterojunction (BHJ) and layer-by-layer (LbL) structure OSCs are successfully achieved featuring a high-power conversion efficiency of 18.10%/18.25%, simultaneously having excellent device stability. This work shows that introducing a low concentration dopant into organic donor is an effective method for improving the electrical performance of organic donor and the efficiency of OSCs.

Glycerol formal is reported as a green solvent for processing efficient and stable quasi-2D (n = 5) metal halide perovskite solar cells.

Abstract

Despite the remarkable advances in the field of perovskite photovoltaics, the use of toxic solvents for their fabrication poses a significant challenge to their scale-up and commercialization. The vast majority of studies rely on using the highly hazardous N, N-Dimethylformamide (DMF), with green alternatives remaining scarce. In this work, the use of glycerol formal (Gly-F) is reported as a green solvent for fabricating quasi-2D (n = 5) perovskite solar cells. Quasi-2D perovskite films processed from Gly-F exhibit a high degree of uniformity and a compact microstructure. When integrated into solar cells, the green solvent-processed films reach a promising power conversion efficiency of 14.53%. This performance is lower than that of DMF-based perovskites, most likely due to the presence of laterally oriented low n perovskite phases. Interestingly, while the performance of DMF-based devices is rather irreproducible, the performance of Gly-F-based devices is robust and consistent. These results demonstrate the potential of Gly-F- as a promising green alternative to DMF.

A series of pH-neutral conjugated polyelectrolytes with high doping density are designed and synthesized as hole-transporting layer materials. The high doping density of PTT-F:POM is proved to significantly decrease the depletion region width at the anode interface, which minimized the energy loss in hole transport. Consequently, a binary organic solar cell modified by PTT-F:POM achieved a high PCE of 18.8%.

Abstract

The lack of effective and non-corrosive hole-transporting layer (HTL) materials has remained a long-standing issue that severely restricts the performance of organic solar cells (OSCs). Most pH-neutral conjugated polyelectrolytes (CPEs) exhibit inferior performance to the acid-doped HTL materials due to their low doping density. In this study, a series of pH-neutral CPEs is designed and synthesized with high doping density as HTL materials. Through an elaborate synthetic route, two sulfonate-terminating alkoxyl side chains can be introduced into thiophene, by which the electron-rich, highly soluble, and chemically stable thiophene monomer is synthesized to enable the subsequent polymerization. The CPE PTT-F exhibit a remarkable self-doping property with an enhanced doping density from 2.01 × 10¹⁷ to 7.02 × 10¹⁸ cm⁻³. The high work function and the increased doping density of PTT-F-based HTL decrease the depletion region width from 38.4 to 8.1 nm at the anode interface, which minimized the energy loss in hole transport. Consequently, a binary OSC modified by PTT-F-based HTL achieve a high PCE of 18.8%. To the best of the knowledge, this is the highest PCE for OSC employing CPE-based HTL. The results from this work demonstrate an encouraging achievement of realizing exceptional hole collection ability in pH-neutral CPEs.

Incorporating dithienophthalimide unit with high dipole moment into PM6 main chain, endows the designed terpolymers with good tetrahydrofuran processability and enhanced crystallinity, resulting in high PCEs of 18.79% and 19.45% for tetrahydrofuran processable binary and ternary blend OSCs.

Abstract

Developing organic solar cells (OSCs) processable with halogen-free, non-aromatic solvents is crucial for practical applications, yet challenging due to the limited solubility of most photoactive materials. This study introduces high-performance terpolymers processable in tetrahydrofuran (THF) by incorporating dithienophthalimide (DPI) into the PM6 backbone. DPI extends the absorption band, lowers HOMO levels, and improves THF solubility and film crystallinity through its large dipole moment effect. Optimal PBD-10:L8-BO devices processed with THF achieved a competitive power conversion efficiency (PCE) of 18.79%, approaching chloroform-processed devices (19.04%). By introducing PBTz-F as a second donor, ternary OSCs reached an impressive 19.45% PCE when processed with THF. This improvement stems from enhanced photon generation, improved morphology, better charge transport, longer exciton lifetimes, efficient charge dissociation and collection, and suppressed recombination. These PCEs of 18.79% and 19.45% for binary and ternary blend OSCs, respectively, represent the highest reported efficiencies for OSCs processed with halogen-free, non-aromatic solvents. This work demonstrates significant progress in eco-friendly OSC fabrication, paving the way for more sustainable and commercially viable organic photovoltaic technologies.

This work proposes an internal encapsulation strategy utilizing the synergistic effect of in situ cross-linking and π-effects, achieving an upgrade of the protective layer from linear to mesh-like coverage. The internal encapsulated device exhibits an enhanced efficiency of 25.31 % and noticeably improved stability.

Abstract

Pursuing high stability becomes the core challenge in realizing the widespread application of perovskite solar cells (PerSCs). Here, a practical internal-capsulation strategy is proposed by introducing cross-linkable methacrylate analogs upon the perovskite layer, hindering ion migration and preventing lead leakage to achieve stable PerSCs. Butyl methacrylate (UMA) and benzyl methacrylate (BMA) can chemically interact with the perovskite layer, especially for the BMA dimer with significant π-interactions among the hanging benzene rings. Such configuration facilitated more compact coordination, thereby restoring the Fermi level of perovskite to a defect-free state and reducing carrier recombination losses. Moreover, by integrating the self-cross-linking and intermolecular π-effect, the application of BMA upgraded the internal capsulation from linear protection to a compact mesh-like scale. Consequently, the application of BMA not only boosted the efficiency to 25.31% but also greatly enhanced the stability of the perovskite layer, especially for water resistance and preventing lead linkage. The internal capsulation strategy upgrading from linear to mesh-like marked an innovative direction in protecting the perovskite layer, paving the way for more sustainable PerSCs in further application.

2,2′-bipyridyl-4,4′-dicarboxylic acid (HBPDC) is incorporated as an interface layer between SnO₂ and perovskite layers in PSCs, passivates the surface defects from both the surfaces, and enhances the interfacial adhesion and mechanical reliability. The resulting PSCs exhibited an outstanding power conversion efficiency (PCE) of 25.41 % with improved stability.

Abstract

The regulation of interfaces remains a critical and challenging aspect in the pursuit of highly efficient and stable perovskite solar cells (PSCs). Here, 2,2′-bipyridyl-4,4′-dicarboxylic acid (HBPDC) is incorporated as an interfacial layer between SnO₂ and perovskite layers in PSCs. The two carboxylic acid moieties on HBPDC bind to SnO₂ through esterification, while its nitrogen atoms, possessing lone electron pairs, interact with uncoordinated lead (Pb²⁺) atoms through Lewis acid-base interactions. This dual functionality enables simultaneous passivation of surface defects on both the SnO₂ and buried perovskite layers. In addition, the electron-deficient nature of HBPDC enhances interfacial energy band alignment and facilitates electron transfer from the perovskite to SnO₂. Furthermore, the incorporation of HBPDC strengthens the interfacial adhesion, improving mechanical reliability. As a result, the PSCs exhibited an impressive power conversion efficiency (PCE) of 25.41 % under standard AM 1.5G conditions, along with remarkable environmental stability.

A perovskite precursor solution using acetonitrile (ACN) as the host solvent is developed to mitigate heterogeneous nucleation induced by the competitive coordination effect of traditional N,N-dimethylformamide (DMF), while also cutting costs by half compared to DMF-based solutions. This study provides valuable insights into solvent interactions during perovskite film formation and offers a cost-effective strategy to enhance device performance.

Abstract

Solution-processing is the primary method for fabricating high-efficiency perovskite solar cells (PSCs), where solvent choice critically influences film formation and quality. Although additives can optimize film formation dynamics by balancing nucleation and growth of perovskite, they can also induce heterogeneous nucleation due to competitive coordination and varying crystallization kinetics, leading to compositional heterogeneity and structural disorders. Herein, a perovskite precursor solution is developed using acetonitrile (ACN) as a weak coordination host solvent instead of the traditional N,N-dimethylformamide (DMF). The ACN-based perovskite precursor solution reduces heterogeneous nucleation typically caused by the competitive coordination effect of DMF, and cuts costs by half compared to DMF-based precursor solutions. This approach promotes a single crystallization pathway via a dimethyl sulfoxide-solvated intermediate phase to α-FAPbI₃, which extends the anti-solvent operation window, and enhances the crystallinity of perovskite films, and reduces defect states. The power conversion efficiencies (PCE) of 23.62% and 20.13% is achieved for the PSC and minimodule, respectively. The PSC retains over 97% of its initial efficiency after 800 h of continuous illumination under maximum power point tracking (MPPT). These findings provide valuable insights into solvent interactions in perovskite film formation and offer a cost-effective strategy for improving the device's performance and stability.

Nylon 11 (N11), a long-chain polymer, is introduced for post-treating grain boundaries (GBs) and surface defects in FAPbI₃, yielding high-quality films with tight GBs, low surface defect density, and enhanced stability against high humidity. Devices treated with N11 achieve efficiencies of up to 23.54%, showcasing improved stability and highlighting the potential of N11 treatment for further advancements in PSCs.

Abstract

Grain boundaries (GBs) and surface defects within perovskite films are inherent challenges that affect the photovoltaic performance of perovskite solar cells  (PSCs. In this work, Nylon 11 (N11) is utilized, a long-chain polymer, for post-treating the GBs and surface defects within FAPbI₃ films. The multifunctional groups of N11 exhibit unique passivation abilities, enabling self-regulation and selective correction of reverse-charged defects. Post-treating with N11 results in high-quality FAPbI₃ films characterized by tight GBs and low surface defect density. Despite fabrication under full open-air conditions, the N11 post-treatment significantly enhances the power conversion efficiency (PCE) value of FAPbI₃ PSCs, increasing it from the reference value of 21.89% to 23.54%. Importantly, the long alkyl chain present in N11 significantly enhances the humidity stability of the PSCs. Unencapsulated PSCs treated with N11 maintain 89% of their initial PCE after exposure to air with 30% relative humidity (RH) for 1000 h, demonstrating resilience to elevated humidity levels. This work highlights the substantial improvement in the photovoltaic performance of PSCs achieved through the post-treatment with N11.

Publication date: 15 December 2024

Source: Nano Energy, Volume 132

Author(s): Xiongzhuo Jiang, Jie Zeng, Kun Sun, Zerui Li, Zhuijun Xu, Guangjiu Pan, Renjun Guo, Suzhe Liang, Yusuf Bulut, Benedikt Sochor, Matthias Schwartzkopf, Kristian A. Reck, Thomas Strunskus, Franz Faupel, Stephan V. Roth, Baomin Xu, Peter Müller-Buschbaum

β-poly(1,1-difluoroethylene) as a ferroelectric polymer dipole is introduced into Sn–Pb perovskite to enhance the built-in electric field and promote the charge transfer at perovskite/electron transport layer interface, which effectively suppresses non-radiative recombination and reduces the interfacial quasi-Fermi Level Splitting deficit. The resultant Sn–Pb perovskite solar cells achieve a champion efficiency of 23.44%, along with enhanced long-term stability.

Abstract

The quasi-Fermi level splitting (QFLS) deficit caused by the non-radiative recombination at the interface of perovskite/electron transport layer (ETL) can lead to severe open-circuit voltage (V _OC) loss and thus decreases the efficiency of perovskite solar cells (PSCs), however, has received limited attention in inverted tin-lead PSCs. Herein, the strategy of constructing an extra-electric field is presented by introducing ferroelectric polymer dipoles (FPD)-β-poly(1,1-difluoroethylene)-to suppress the QFLS deficit. The directional polarization of FPD can enhance the built-in electric field (BEF) and thus promote the charge transfer at the perovskite/ETL interface, which effectively suppresses non-radiative recombination. Furthermore, the incorporation of FPD facilitates high-quality crystallization of perovskite and reduces the surface energetic disorder. Therefore, the QFLS deficit in the perovskite/ETL half-stacked device is reduced from 62 to 27 meV after incorporating FPD, and the optimized device achieves an efficiency of 23.44% with a high V _OC of 0.88 V. Additionally, the addition of FPD increases the activation energy for ion migration, which can reduce the effect of ion migration on the long-term stability of the device. Consequently, the FPD-incorporated device retains 88% of the initial efficiency after 1100 h of continuous illumination at the maximum power point (MPP).

Nature, Published online: 14 October 2024; doi:10.1038/s41586-024-08160-y

Nature, Published online: 14 October 2024; doi:10.1038/s41586-024-08161-x

Nature, Published online: 14 October 2024; doi:10.1038/s41586-024-08158-6

Utilizing naturally abundant and environmentally friendly resveratrol (RES) as an additive in perovskite. The coordination effect of RES's C═C and phenolic hydroxyl groups with the uncoordinated Pb²⁺ in the perovskite leads to improved energy level alignment and reduced grain boundary defects. With enhanced long-term stability, the power conversion efficiency reached a satisfactory 23.44%.

Abstract

The stability of perovskite solar cells is closely related to the defects in perovskite crystals, and a large number of crystal defects are caused by the solution method. In this study, resveratrol (RES), a green natural antioxidant abundant in knotweed and grape leaves, is introduced into perovskite films to passivate the defect. RES achieves defect passivation by interacting with uncoordinated Pb²⁺ in perovskite films. The defect formation energy of V_Pb and Pb_I on the surface of perovskite thin films is increased by RES doping, as calculated by density functional theory. The results show that the quality of the perovskite film is significantly improved, and the energy level structure of the device is optimized, and the power conversion efficiency (PCE) of the device is increased from 21.62% to 23.44%. RES can hinder the degradation of perovskite structures by O₂ ⁻ free radicals, and the device retained 88% of its initial PCE after over 1000 h in pure oxygen environment. The device retains 91% of the initial PCE after >1000 h at 25 °C and 50 ± 5% relative humidity. This work provides an idea for the use of natural and environmentally friendly additives to improve the efficiency and stability of devices.

An organic/inorganic hybrid polyoxometalate is developed to reinforce the halide perovskite ABX₃ structure, involving the strategic regulation of cationic components to passivate A-site vacancy defects and metal ions to enhance electron shuttling at B- and X-site defects. The resulting device achieves an efficiency exceeding 25% with improved durability, showing the promise of using functional polyoxometalates to improve perovskite photovoltaics.

Abstract

Ionic hybrid perovskites face challenges in maintaining their structural stability against non-equilibrium phase degradation, therefore, it is essential to develop effective ways to reinforce their corner-shared [PbI₆]⁴⁻ octahedral units. To strengthen structural stability, redox-active functional polyoxometalates (POMs) are developed and incorporated into perovskite solar cells (PSCs) to form a robust polyoxometalates/perovskite interlayer for stabilizing the perovskite phase. This approach offers several advantages: 1) promotes the formation of an interfacial connecting layer to passivate interfacial defects in addition to stabilize the [PbI₆]⁴⁻ units through exchanged ammonium cations in POMs with perovskites; 2) facilitates continuous structural repairing of Pb⁰- and I⁰-rich defects in the [PbI₆]⁴⁻ unit through redox electron shuttling of the electroactive metal ions in POMs; 3) provides guidance for selecting suitable redox mediators based on the kinetic studies of POM's effectiveness in reacting with targeted defects. The POM-reinforced device maintains 97.2% of its initial PCE after 1500 h of shelf-life test at 65 °C, while also enhancing the long-term operational stability. Additionally, this approach can be generally applicable across scalable sizes and various bandgap perovskites in devices, showing the promise of using functional POMs to enhance perovskite photovoltaic performance.

Optimization of crystallinity and morphology of perovskite by modulation mixed ligands of 2-pyrrolidone and N-methyl-2-pyrrolidone. Based on this strategy, the champion device achieves a power conversion efficiency (PCE) of 24.20% (certified PCE of 23.81%) and 22.13% on an aperture area of 0.0875 and 22.96 cm², respectively.

N-Methyl-2-pyrrolidone (NMP) has become one of the mainstream Lewis base ligand solvents for the fabrication of high-quality FA-based perovskite films. However, the NMP-based perovskite films with small grain sizes always own a mirror surface which will increase the reflection of light and limit the current of perovskite solar cells (PSCs). In this work, 2-pyrrolidone (NP) with a higher boiling point and stronger binding to precursor components is introduced into the precursor solution to improve the crystallization and morphology of perovskite. Finally, a rougher perovskite film with a larger grain size can be fabricated via an optimized NP and NMP mixed ligand solvent. Based on this strategy, the champion device achieved a power conversion efficiency (PCE) of 24.20% (certified PCE of 23.81%) and 22.13% on an aperture area of 0.0875 and 22.96 cm², respectively. In addition, the introduction of NP enhances the humidity and light stability of the film, and the device retained 94.1% of its initial efficiency after 120 h.

These results demonstrate that the addition of BTP-OS with a lower total average electrostatic potential value and slightly higher molecular polarization index compared to the host acceptor can improve the morphology and suppress non-radiative energy loss to achieve a superior ternary device efficiency of 19.72%. This work provides a new perspective to design the ternary strategy.

Abstract

The ternary strategy has proven effective in enhancing the performance of organic solar cells (OSCs), yet identifying the optimal third component remains a challenge due to the lack of theoretical frameworks for predicting its impact based on molecular structure. This study addresses this challenge by proposing quantitative parameters derived from molecular surface electrostatic potential (ESP) as criteria for selecting ternary components. The asymmetric acceptor BTP-OS, which exhibits a lower total average ESP and larger molecular polarization index relative to the host acceptor, is introduced into the PM6:L8-BO system. This incorporation led to weakened ESP-induced intermolecular interactions and reduce miscibility with donor polymer, resulting in an optimized multi-scale morphology of the ternary blend. Consequently, the ternary device achieved an efficiency of 19.72%, one of the highest values for PM6:L8-BO-based ternary devices, with enhanced exciton dissociation and charge collection, lower energy disorder, and minimized non-radiative energy losses. Comparable efficiency improvements are also verified in PM6:BTP-eC9 and D18:N3 systems, demonstrating the broad applicability of the proposed approach. This study not only provides a practical and effective principle for selecting ternary components but also establishes a broader framework for optimizing ternary OSCs, potentially advancing the development of more efficient OSCs across diverse material systems.

Depending on functional organoamines, efficient tin–lead mixed perovskite (TLP) solar cell is achieved by synergistically passivating TLP film grain boundary and buried interface with poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate).

Abstract

Due to its extreme susceptibility of tin to oxidation, the power conversion efficiency (PCE) of tin–lead mixed perovskite (TLP) solar cells still lags far behind the pure lead halides perovskite solar cells (PSCs). More than the endeavors of the suppression of tin-oxidation in the bulk TLP films, the synergistic interface engineering of both grain boundaries and interfaces turns more and more important. Here, a synergistic co-passivation strategy is reported by modulating poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) substrate with p-guanidinobenzonitrile hydrochloride (CG) and grain boundary passivation of TLP film with 3-cyano-4-hydrazinylbenzoic acid (3C-HBA), realizing a competitive device PCE of 23.3%, positioning it at the forefront of reported literature. Strikingly, the discovery of CG modifications for such important PEDOT:PSS layer. Moreover, relying on the comprehensive spectroscopies, 3C-HBA is revealed to effectively modulate the crystallization process of TLP films. This co-passivation strategy obviously reduces trap density and suppresses Sn²⁺ oxidation of TLP devices.

An in situ passivation (ISP) method is introduced to adjust the crystal growth kinetics and obtain the (111)-orientated perovskite films with the passivated boundaries and interfaces, leading to high-performance inverted perovskite solar cells, with power conversion efficiencies (PCEs) of 26.7% (certified as 26.09% at a 5.97 square millimeters active area).

Abstract

Lead halide perovskite solar cells (PSCs) have emerged as one of the influential photovoltaic technologies with promising cost-effectiveness. Though with mild processabilities to massive production, inverted PSCs have long suffered from inferior photovoltaic performances due to intractable defective states at boundaries and interfaces. Herein, an in situ passivation (ISP) method is presented to effectively adjust crystal growth kinetics and obtain the well-orientated perovskite films with the passivated boundaries and interfaces, successfully enabled the new access of high-performance inverted PSCs. The study unravels that the strong yet anisotropic ISP additive adsorption between different facets and the accompanied additive engineering yield the high-quality (111)-orientated perovskite crystallites with superior photovoltaic properties. The ISP-derived inverted perovskite solar cells (PSCs) have achieved remarkable power conversion efficiencies (PCEs) of 26.7% (certified as 26.09% at a 5.97 mm² active area) and 24.5% (certified as 23.53% at a 1.28 cm² active area), along with decent operational stabilities.

Employing the end-extended conjugation strategy, high efficiency, excellent thermal stability, and outstanding mechanical robustness of APSCs are simultaneously achieved. These devices maintain 90 % of their initial PCE for 1500 h at 65 °C, exhibit a high COS value of 24.1 %, and achieve a record-breaking PCE of 19.12 % (certified at 18.45 %).

Abstract

Concurrently achieving high efficiency, mechanical robustness and thermal stability is critical for the commercialization of all-polymer solar cells (APSCs). However, APSCs usually demonstrate complicated morphology, primarily attributed to the polymer chain entanglement which has a detrimental effect on their fill factors (FF) and morphology stability. To address these concerns, an end-group extended polymer acceptor, PY-NFT, was synthesized and studied. The morphology analysis showed a tightly ordered molecular packing mode and a favorable phase separation was formed. The PM6 : PY-NFT-based device achieved an exceptional PCE of 19.12 % (certified as 18.45 %), outperforming the control PM6 : PY-FT devices (17.14 %). This significant improvement highlights the record-high PCE for binary APSCs. The thermal aging study revealed that the PM6 : PY-NFT blend exhibited excellent morphological stability, thereby achieving superior device stability, retaining 90 % of initial efficiency after enduring thermal stress (65 °C) for 1500 hours. More importantly, the PM6 : PY-NFT blend film exhibited outstanding mechanical ductility with a crack onset strain of 24.1 %. Overall, rational chemical structure innovation, especially the conjugation extension strategy to trigger appropriate phase separation and stable morphology, is the key to achieving high efficiency, improved thermal stability and robust mechanical stability of APSCs.

Versatile organic salt additive, 4-(trifluoromethyl) benzylammonium formate (TEMBAFa), is introduced into the perovskite precursor and deposited at the bottom of the perovskite layer, effectively passivating the buried perovskite surface and resolving the issue of delamination.

The merits of a low-cost fabrication process, suitable band structure, excellent wettability to perovskite precursor, and outstanding stability ensure NiO _x as a hole transport material with beneficial characteristics to construct high-performance perovskite solar cells (PSCs). However, direct contact between perovskite and NiO _x causes delamination and chemical instability and thus results in poor carrier transport and short device lifespan. Here, we propose a solution for this issue by introducing an organic salt additive 4-(trifluoromethyl) benzylammonium formate (TFMBAFa) in the perovskite precursor to passivate perovskite film and NiO _x @(2-(3,6-dimethyl-9H-carbazol-9-yl) ethyl) phosphonic acid (Me-2PACz) composited hole transport layer (HTL), and thus construct a buffer layer between perovskite-HTL interface. The effective diminishing of NiO _x /perovskite interfacial reactions and defects results in enhanced carrier transport. Consequently, the target device achieves simultaneous improvements in power conversion efficiency (24.2%), storage stability (T100 > 1400 h), thermal stability (T80 > 1000 h), and operational stability (T70 > 850 h), where T100, T80, and T70 refer to the retention of 100%, 80%, and 70% of initial PCE, respectively. This work provides an effective strategy to advance the performance of NiO _x -based inverted PSCs.

The incorporation of highly conjugated spacers has led to the development of efficient and stable 2D/3D PSCs. These organic spacers enhance charge transport and improve resistance to moisture and ion migration, resulting in enhanced PCE of 21.0 % in 24.8-cm² modules. Furthermore, the devices maintained over 90 % of their initial PCE after 3000 hours of operation under MPP tracking, establishing them as one of the most stable 2D/3D PSCs to date.

Abstract

Incorporating two-dimensional (2D) perovskite in 3D perovskite absorber holds great potential to improve the stability and efficiency of perovskite solar cells (PSCs). However, the bulky-cation-based 2D structures often exhibit poor charge transport and are prone to formation of charge-extraction barrier that impedes efficient device operation. We address these issues by introducing aromatic spacers with molecular conjugation into 2D perovskites locating between 3D perovskites and electron charge transport layers. Among our tested aromatic spacers, the pyrenylbutanamine (PyBA) spacer was shown to endow 2D perovskites with superior charge transport properties and efficient charge extraction from the bulk perovskite in 2D/3D PSCs, due to the highest degree of conjugation. As a result, we achieved a power conversion efficiency (PCE) of up to 25.3 % in a 0.16-cm² single cell and 21.0 % in a 24.8-cm² module. Moreover, the incorporated PyBA substantially raised the resistance of 2D/3D PSCs against moisture and ion migration, resulting in enhanced environmental, thermal, and operational stability. Notably, the PyBA-based devices retained over 90 % of their initial PCE after 2000 hours at 25 °C and 80 % relative humidity, or 1000 hours at 85 °C and 85 % humidity, or 3000 hours of operation under continuous 1-Sun illumination at 40 °C, showcasing their exceptionally high stability compared to previously reported 2D/3D PSCs.