Chen Weijie

By employing a surface planarization strategy, a uniform and dense p-i-n 2D/3D heterojunction is successfully developed. This approach has enabled planarized 2D/3D PSCs and modules to achieve remarkable efficiencies of 26.02% for a 0.1 cm² area and 23.06% for a 22.8 cm² area, primarily by suppressing interface nonradiative recombination. Additionally, these devices exhibit exceptional operational stability under accelerated testing protocols.

Abstract

Two-dimensional/three-dimensional (2D/3D) halide perovskite heterojunctions are widely used to improve the efficiency and stability of perovskite solar cells. However, interfacial defects between the 2D and 3D perovskites and the poor coverage of the 2D capping layer still hinder long-term stability and homogeneous charge extraction. Herein, a surface planarization strategy on 3D perovskite is developed that enables an epitaxial growth of uniform 2D/3D perovskite heterojunction via a vapor-assisted process. The homogeneous charge extraction and suppression of interfacial nonradiative recombination is achieved by forming a uniform 2D/3D interface. As a result, a stabilized power output efficiency of 25.97% is achieved by using a 3D perovskite composition with a bandgap of 1.55 eV. To demonstrate the universality of the strategy applied for different perovskites, the champion device based on a 1.57 eV bandgap 3D perovskite results in an efficiency of 25.31% with a record fill factor of 87.6%. Additionally, perovskite solar modules achieve a designated area (24.04 cm²) certified efficiency of 20.75% with a high fill factor of 80.0%. Importantly, the encapsulated uniform 2D/3D modules retain 96.9% of the initial efficiency after 1246 h operational tracking under 65 °C (ISOS-L-3 protocol) and 91.1% after 862 h under the ISOS-O-1 protocol.

A multifunctional and universal molecular complexation strategy is developed, which simultaneously stabilizes hole transport layer (HTL), perovskite layer and Ag electrode by the suppression of Li⁺, I⁻ and Ag migration via directly incorporating bis(2,4,6-trichlorophenyl) oxalate (TCPO) into HTL. TCPO-doped regular device achieves a certified power conversion efficiency of 25.59 %, which is accompanied by excellent operational stability.

Abstract

The migration and diffusion of Li⁺, I⁻ and Ag impedes the realization of long-term operationally stable perovskite solar cells (PSCs). Herein, we report a multifunctional and universal molecular complexation strategy to simultaneously stabilize hole transport layer (HTL), perovskite layer and Ag electrode by the suppression of Li⁺, I⁻ and Ag migration via directly incorporating bis(2,4,6-trichlorophenyl) oxalate (TCPO) into HTL. Meanwhile, TCPO co-doping results in enhanced hole mobility of HTL, advantageous energy band alignment and mitigated interfacial defects, thereby leading to facilitated hole extraction and minimized nonradiative recombination losses. TCPO-doped regular device achieves a peak power conversion efficiency (PCE) of 25.68 % (certified 25.59 %). The unencapsulated TCPO doped devices maintain over 90 % of their initial efficiencies after 730 h of continuous operation under one sun illumination, 2800 h of storage at 30 % relative humidity, and 1200 h of exposure to 65 °C, which represents one of the best stabilities reported for regular PSCs. This work provides a new approach to enhance the PCE and long-term stability of PSCs by host–guest complexation strategy via rational design of multifunctional ligand molecules.

Nature Photonics, Published online: 04 November 2024; doi:10.1038/s41566-024-01561-5

Publication date: 15 December 2024

Source: Nano Energy, Volume 132

Author(s): Ghulam Dastgeer, Sobia Nisar, Muhammad Wajid Zulfiqar, Jonghwa Eom, Muhammad Imran, Kamran Akbar

Publication date: 15 January 2025

Source: Joule, Volume 9, Issue 1

Author(s): Yunjie Dou, Siwei Luo, Pengchen Zhu, Liangxiang Zhu, Guangye Zhang, Chunxiong Bao, He Yan, Jia Zhu, Shangshang Chen

A novel fluorocarbon-solvents bath annealing approach is developed, and the previously neglected solvent-to-solvent interaction between two fluorocarbon solvents, perfluorodecalin (PFD) and perfluorotoluene (PFT), and perovskite precursor solvents (e,g, dimethyl sulfoxide) is investigated to achieve highly crystalline and enlarged grain size of perovskite films. The resulting planar solar cell achieves a remarkable improved efficiency of 24.26% with suitability for large-area devices.

Abstract

Thermal annealing is a critical process in producing high-quality perovskite films for high-performance perovskite solar cells. Conventional TA presents challenges such as delayed heat transfer, leading to unwanted crystal growth and hindering processing scalability. Solvent-bath annealing is an attractive approach that can improve heat transfer and promote perovskite crystallization by immersing the as-deposited precursor film in a liquid medium. In this study, fluorocarbon-based solvents are developed as novel solvent baths for uniform heat flow through omnidirectional annealing. In addition, the previously neglected solvent-to-solvent interaction between fluorocarbon and solvents for perovskite precursor is investigated by comparing two fluorocarbon solvents. By increasing the solvent-solvent interaction, higher quality perovskite films with increased crystallinity, improved perovskite transition, and reduced film defects are achieved. As a result, the perovskite solar cells exhibited an increased power conversion efficiency with excellent reproducibility. These findings suggest that the selection of suitable solvent bath is promising for further improving perovskite quality and device performance.

A multisite atomic-oxygen anchoring strategy using 1,1,2,2-tetra(4-methoxyphenyl)ethene (TMPE) is investigated for its potential to enhance perovskite photovoltaic performance. TMPE coordinates iodine vacancies and passivates Pb²⁺ or MA⁺ defects, as confirmed by density functional theory calculations. This method improves crystallinity, surface defect passivation, and photovoltaic efficiency, achieving outstanding stability and efficiency in both MA- and FA-based perovskite solar cells.

Abstract

Lewis base molecules are widely used to passivate structural defects in perovskites. However, the spatial compatibility between these molecules and the perovskite lattice is seldom considered. Herein, a multisite atomic-oxygen (O) anchoring passivation strategy using 1,1,2,2-tetra(4-methoxyphenyl)ethene (TMPE), which contains four electronegative O atoms to selectively anchor iodine vacancies and passivate under-coordinated Pb²⁺ or MA⁺ defects is proposed. It is found that the distance between any three O atoms in a TMPE molecule matches that of iodine ions in the lattice structure, thereby maximizing passivation effects and enhancing lattice stability. Additionally, the coordination of TMPE facilitates the formation of larger colloid sizes in the precursor solution, effectively regulating crystal growth. Due to the molecular extrusion effect, TMPE-based anchors localize on the surface, passivating defects and mitigating nonradiative recombination. As a result, defects in MA-based and FA-based perovskite films are significantly reduced, achieving optimized power conversion efficiencies (PCEs) of 19.9% and 24.5%, while exhibiting exceptional stability by retaining 90% of initial PCE after 1200 h of storage without encapsulation. This single molecule-controlled perovskite multisite anchoring strategy would help resolve lattice stability issue caused by perovskite defects, thereby paving the pathway for the development of high-performance and highly stable perovskite solar cells.

The development of a conformal, low-temperature processable all-SnO₂-based electron transport layer (ETL) on high-haze FTO substrates significantly enhances perovskite solar cells (PSCs) performance. The ALD SnO₂ layer provides a dense hydroxyl surface for optimal anchoring of a polyacrylic acid-stabilized quantum dot-SnO₂ layer, resulting in reduced carrier recombination, improved electron transport, and a power conversion efficiency of up to 24.97%.

Abstract

The fabrication of high-performance perovskite solar cells on high-haze fluorine-doped tin oxide (FTO) substrates with superior light-trapping capabilities necessitates a highly conformal electron transport layer at the bottom interface. Herein, a conformal low-temperature processable all-SnO₂-based electron transport layer (ETL) is successfully developed on high-haze FTO by well-anchoring a polyacrylic acid-stabilized quantum dot-SnO₂ layer onto an atomic layer deposited SnO₂ layer with a dense hydroxyl surface. The obtained ETL demonstrates excellent capabilities in simultaneously homogenizing the surface contact potential distribution, blocking hole transport, and suppressing non-radiative recombination. Consequently, a champion device is achieved that delivers a remarkable power conversion efficiency (PCE) of up to 24.97%, with V_OC × FF reaching 87.09% of the Shockley-Queisser limit at a bandgap of 1.54 eV, which is the highest value among the ALD SnO₂-based PSCs. The homogeneous ETL further enabled the fabrication of a 1 cm² PSC with a PCE of 23.18% and only a 10 mV loss in V_OC compared to smaller-area PSCs, showcasing its potential for large-scale commercial applications.

2D perovskites, especially phase-pure structures, offer improved stability and efficiency. This review explores the crystal structure design, formation mechanisms, characterization techniques, synthesis methods, and solar cell performance of phase-pure 2D perovskites. It highlights the connection between structural design and performance enhancement for understanding the application of phase-pure 2D perovskites in solar cells.

Abstract

2D perovskite structures have gained significant attention due to their reliable long-term stability. Unlike quasi-2D perovskites, phase-pure 2D perovskites exhibit a flattened energy landscape and low energy transfer losses, offering substantial benefits for enhancing device efficiency and stability. Recent research on phase-pure 2D perovskites has shown significant progress, attributed to their unique properties. This review delineates advancements in the study of phase-pure 2D perovskite materials and elucidates the relationships between crystal structure design, growth, and device performance regulation. Additionally, it summarizes techniques for characterizing phase-pure 2D structures and methods for their precise synthesis. Finally, an outlook on the future development of phase-pure 2D perovskites, highlighting the scientific and technological challenges in current research is provided.

The 5-fluoropyridinic acid (FPA) self-induced bifacial passivation strategy not only effectively passivates the uncoordinated Pb/Pb²⁺ at the upper and lower interfaces of the perovskite films, but also improves the quality of the films. Furthermore, due to the matching of the energy levels, the extraction rate of the carriers at the bifacial interface is simultaneously improved.

Abstract

The uncontrolled crystallization of perovskite generates a significant number of internal and interfacial defects, posing a major challenge to the performance of perovskite solar cells (PSCs). In this paper, a novel bi-interfacial modification strategy utilizing 5-fluoropyridinic acid (FPA) is proposed to modulate crystal growth and provide defect passivation. It is demonstrated that FPA is self-deposited at both the top and bottom interfaces of perovskite films during thermal annealing. The CO and N functional groups in FPA serve as chelating agents, binding closely to uncoordinated Pb²⁺/Pb clusters, thereby passivating defects and reducing charge recombination at the interfaces. The strong chemical interactions between FPA and Pb further stabilize the Pb-I framework, promoting the formation of high-quality perovskite films, as confirmed by in situ photoluminescence measurements. Consequently, the modified inverted PSCs achieved an exceptional power conversion efficiency (PCE) of 25.37%. Moreover, the devices retained over 93.17% of initial efficiency after 3000 h of continuous illumination under one-sun equivalent conditions in a nitrogen atmosphere. This paper presents a promising pathway for enhancing the performance and stability of inverted PSCs through a self-induced bi-interfacial modification approach.

The performance of PBDBT: N2200-based all-polymer solar cells can be enhanced by processing with dilute diiodooctane solvent additive. This study reveals the microstructural mechanisms that drive charge transport enhancements in these solar cells by combining X-ray techniques with electron microscopy. Ultimately, the study finds that processing with dilute diiodooctane promotes efficient vertical charge transport pathways while preserving donor–acceptor interfacial connectivity.

Abstract

The performance of all-polymer solar cells is often enhanced by incorporating solvent additives during solution processing. In particular, blends based on the model all-polymer system PBDBT:N2200 have been shown to have increased short-circuit current and fill factor when processed with dilute diiodooctane (DIO). However, the morphological mechanism that drives the increase in performance is often not well understood due to limitations in common characterization techniques. In this study, it is shown that a combination of X-ray techniques with cryogenic high-resolution transmission electron microscopy (HRTEM) analysis can provide a quantitative and spatially resolved picture of polymer chain orientation and alignment in all-polymer blends. It is found that DIO induces vertical phase separation in PBDBT-2F:F-N2200 and increases donor crystallite thickness in the pi-stacking direction leading to an acceptor-rich film surface. However, it is also shown that DIO does not disrupt the formation of face-on donor–acceptor interfaces. These findings suggest that dilute DIO primarily affects crystalline domain formation in single component regions as opposed to mixed regions; thus, dilute DIO can impact vertical charge transport pathways without sacrificing donor–acceptor interfacial connectivity.

Doping, the controlled addition of imperfections or impurities to a material, is crucial for semiconductors. This study shows that for Halide Perovskites, which have (very) low (intrinsic) defect densities because of effective self-healing and defect tolerance, the title's statement holds in an unprecedented fashion.

Abstract

The (opto)electronic behavior of semiconductors depends on their (quasi-)free electronic carrier densities. These are regulated by semiconductor doping, i.e., controlled “electronic contamination”. For metal halide perovskites (HaPs), the functional materials in several device types, which already challenge some of the understanding of semiconductor properties, this study shows that doping type, density and properties derived from these, are to a first approximation controlled via their surfaces. This effect, relevant to all semiconductors, and already found for some, is very evident for lead (Pb)-HaPs because of their intrinsically low electrically active bulk and surface defect densities. Volume carrier densities for most polycrystalline Pb-HaP films (<1 µm grain diameter) are below those resulting from even < 0.1% of surface sites being electrically active defects. This implies and is consistent with interfacial defects controlling HaP devices in multi-layered structures with most of the action at the two HaP interfaces. Surface and interface passivation effects on bulk electrical properties are relevant to all semiconductors and are crucial for developing those used today. However, because bulk dopant introduction in HaPs at controlled ppm levels for electronic-relevant carrier densities is so difficult, passivation effects are vastly more critical and dominate, to first approximation, their optoelectronic characteristics in devices.

Nature Energy, Published online: 30 October 2024; doi:10.1038/s41560-024-01660-1

Charge separation mechanism in state-of-the-art system has been a part of intense debate. Here, it is presented that as, the system moves toward the low-offset regime the thermal contribution plays an important role to derive the charge separation. The rational guide is provided to achieve the maximum CSE and maximum V _OC simultaneously within the mid-offset regime.

Abstract

In recent years, organic solar cells (OSCs) have shown high power efficiencies approaching 20%. However, the fundamental mechanisms of charge separation in these highly efficient devices have been a subject of intensive debates. Here, the charge separation efficiency (CSE) is extensively investigated across a wide range of blend systems with different energetic offsets. The findings unveil the temperature-dependent nature of charge separation in low-offset systems, emphasizing its significant contribution to the overall CSE. An intriguing inverse correlation between CSE and charge separation activation energy in relation to the offset is also observed. These results shed new light on the factors underlying the high CSE observed in the state-of-the-art devices.

This mini-review discusses the challenges of lead halide perovskite solar cells under environmental stressors, which led to uncoordinated lead ions escaping from the lattice. The review article highlights the role of ligands in mitigating lead ions through hydrogen bond formation, enhancing structural integrity, and defect passivation.

Abstract

Lead halide perovskite solar cells (PSCs) have demonstrated power conversion efficiencies comparable to silicon-based solar cells, yet their instability under environmental stressors, such as humidity, heat, and light, remains a significant barrier to commercialization. A primary cause of this instability is the uncoordinated lead ions (Pb²⁺), which accelerates the degradation of PSCs and pose environmental concerns due to potential lead leakage. Recently, the introduction of ligands into PSCs has shown promise in mitigating lead toxicity through effective passivation, primarily by forming hydrogen bonds (H-bonds) between functional groups of the ligands and the perovskite structure. In this minireview, we explore the critical role of H-bonds in stabilizing PSCs by enhancing the structural integrity of the perovskite layer and reducing lead leakage. Furthermore, we discuss the contribution of these ligands in defect passivation, hydrophobicity, self-encapsulation, cross-linking, and self-healing mechanisms. These insights will highlight the multi-functional capabilities of ligands in improving the long-term stability and durability of PSCs, offering pathways to address current challenges in their commercialization.

Nature Photonics, Published online: 28 October 2024; doi:10.1038/s41566-024-01541-9

An efficient and bright silicon-based top-emission perovskite light-emitting diode emitting at green band is demonstrated through the introduction of a highly reflective Ag bottom electrode modified with MoO₃/[2-(9H-carbazol-9-yl) ethyl] phosphonic acid, leading to a maximum external quantum efficiency of 18.2% and a high brightness of 81931 cd m⁻² that are on par with those of the red and near-infrared counterparts.

Abstract

The integration of perovskites with mature silicon platform has emerged as a promising approach in the development of efficient on-chip light sources and high-brightness displays. However, the performance of Si-based green perovskite light-emitting diodes (PeLEDs) still falls significantly short compared to their red and near-infrared counterparts. In this study, it is revealed that the high work function Au, widely employed in Si-based top-emission PeLEDs as the reflective bottom electrode, exhibits considerably lower reflectivity in the green spectrum than in the longer wavelengths. Consequently, Ag electrode is introduced to replace Au to enhance the green light reflectivity, and the ultrathin MoO₃ and self-assembled monolayers (SAMs) are sequentially deposited for surface modification. These results indicate that the MoO₃ layer removes the energy barrier at Ag/polymer hole transport layer interface, enhancing the hole injection efficiency; while the SAMs firmly anchor onto the MoO₃ layer, effectively preventing interfacial defect formation. Benefited from this organic/inorganic dual-layer modification strategy, Si-based green PeLEDs with an impressive peak external quantum efficiency of 18.2% and a maximum brightness of 81931 cd m⁻² are successfully fabricated, on par with those of the red and near-infrared counterparts. This achievement marks an advancement in developing high-performance Si-based PeLEDs with full-spectrum output.

An effective strategy of bimolecular passivation-dipole bridge is developed to reconstruct perovskite electron-selective contact, significantly promoting electron extraction for achieving highly efficient inverted perovskite solar cells with low nonradiative recombination loss.

Abstract

Constructing charge-selective heterointerface with minimized defect state and matched energy level alignment is essential to reduce nonradiative recombination for achieving high-performance perovskite solar cells (PSCs). Herein, a bimolecular passivation-dipole bridge comprised of sodium phenylmethanesulfonate (SPM) and 2-phenylethylammonium iodide (PEAI) is carefully developed to regulate perovskite heterointerface. SPM passivates defect states and upshifts Fermi level (E _F) of perovskite surface, and subsequent PEAI further induces additional negative dipole and causes the surface E _F of perovskite pinning to negative polaron transport state of electron transport layer PCBM, which significantly promotes electron extraction at the perovskite electron-selective contact. These advantages are confirmed by a remarkably improved efficiency from 21.74% for control to 25.12% for treated PSC with excellent stability. Moreover, corresponding nonradiative recombination loss impressively diminishes from 123 to 70 meV, and charge transport-induced fill factor loss is only 3.00%. This work provides a promising approach via passivation-energetic synergy for engineering perovskite heterointerface toward highly efficient and stable PSCs.

Publication date: 15 December 2024

Source: Nano Energy, Volume 132

Author(s): Ming-Hsuan Yu, Xingyu Liu, Hao-Wei Yu, Shih-Feng Kao, Chiung-Han Chen, Yu-Cheng Tseng, I.-Chih Ni, Bi-Hsuan Lin, Yang Wang, Chu-Chen Chueh

Poor transport within the transport layers in halide perovskites can result in collection losses with increasing absorber thickness, which is often observed in cases of low absorber mobilities. This suggests that different optimization strategies for a better charge collection may be required by enhancing the absorber mobility if it is low, while improving the transport-layer mobility is the preferred strategy when the absorber-layer mobility is sufficient.

Abstract

The collection of photogenerated charges in halide perovskite solar cells depends on the thickness of the absorber layer, with larger thicknesses leading to a reduced collection efficiency. This observation has traditionally been associated with insufficiently high electron and hole diffusion lengths in the absorber layers. However, it is shown that in the presence of low-mobility contact layers, charge collection can be thickness-dependent, even if the absorber layer has infinite mobility. Here, analytical equations are derived for the thickness dependence of charge collection losses in situations where recombination is bulk or interface-limited and show how to relate these equations to voltage-dependent photoluminescence data. The analytical equations are compared to experimental data and numerical simulations and it is observed that experimental data on triple-cation perovskite devices with different thicknesses approximately follows the case, where bulk recombination dominates.

The two-step air-processed efficient PSCs with full lifecycle management are effectively realized by the polymer-stabilized precursor ink. The modified PSCs deliver an impressive efficiency of 25.18% with superior environmental and mechanical stability. The end-of-life PSCs with lead leakage suppression and device regeneration will not pose a threat to the environmental and biological safety.

Abstract

Despite the outstanding power conversion efficiency of perovskite solar cells (PSCs) realized over the years, the entire lifecycle from preparation and operation to discarding of PSCs still needs to be carefully considered when it faces the upcoming large-scale production and deployment. In this study, bio-derived chitin-based polymers are employed to realize the full lifecycle regulation of air-processed PSCs by forming multiple coordinated and hydrogen bonds to stabilize the lead iodide and organic salt precursor inks, accelerating the solid–liquid reaction and crystallization of two-step deposition process, then achieving the high crystalline and oriented perovskites with less notorious charge defects in the open air. The air-prepared PSCs exhibit a decent efficiency of 25.18% with high preparation reproducibility and improved operational stability toward the harsh environment and mechanical stress stimuli. The modified PSCs display negligible fatigue behavior with keeping 92% of its initial efficiency after operating for 32 diurnal cycles (ISOS-LC-1 protocol). Meanwhile, closed-loop lead management of end-of-life PSCs including suppression of lead leakage, toxicity evaluation of broken devices, and recycling of lead iodide components are comprehensively investigated. This work sheds light on a promising avenue to realize the entire lifecycle regulation of air-processed efficient and stable PSCs.

A suitable solvent system of passivator can maximize the passivation effect, further improving the photovoltaic performance of perovskite solar cells (PSCs). This work proposes a ternary solvent system of 4-MeO-PEAI, which can inhibit the solvent-induced additional defects and achieve a sufficient passivated perovskite surface simultaneously. The resulting PSCs achieve an impressive power conversion efficiency (PCE) of 26.05%, and the devices can maintain 95.23% and 95.68% of their initial PCE after 2000 h storage in ambient air and 800 h light-soaking in N₂-glovebox.

Abstract

Surface passivation is a vital approach to improve the photovoltaic performance of perovskite solar cells (PSCs), in which the passivator solvent is an inevitable but easy-ignored factor on passivation effects. Herein, a universal ternary solvent system of surface passivators is proposed through comprehensively considering the solubility and selective perovskite dissolution of the solvent to maximize the passivation effect. Tetrahydrothiophene 1-oxide (THTO) is selected as the passivation promoter by comparing the binding energy with perovskite and the ability to distort the perovskite lattice among various aprotic polar solvent molecules, which can facilitate the passivator's reaction with perovskite and achieve sufficient passivation on perovskite surface. Besides, chlorobenzene (CB) is used as the diluting agent to minimize the amount of isopropanol (IPA), inhibiting the additional solvent-induced defects. As a result, the planar PSCs achieve a power conversion efficiency (PCE) of 26.05%, (certificated 25.66%). Besides, the unencapsulated devices exhibit enhanced stability, which can maintain 95.23% and 95.68% of their initial PCE after 2000 h of storage in ambient air and 800 h of light-soaking in N₂-glovebox. Moreover, this ternary solvent system also exhibits a well applicability and reliability in different passivator such as PEAI, BAI, and so on.

This study introduces three novel SAMs in perovskite solar cells, with a pyrene-based SAM (4PAPyr) showing optimal energy level alignment and outperforming the commercial 2PACz. 4PAPyr enhances device performance, improves surface coverage, and achieves 22.2% power conversion efficiency, highlighting the importance of diversifying SAMs to unlock further efficiency and scalability improvements in perovskite solar cells.

Abstract

Recently, the efficiency of p-i-n perovskite solar cells drastically increased, a pivotal factor being the incorporation of self-assembled monolayers (SAMs) as a hole-transporting layer (HTL). SAMs offer many advantages over conventional HTLs, including minimal material requirements, low cost, and facile processing. Current research is mainly focused on the development of carbazole-derived SAMs. However, the versatility of organic chemistry allows for the design of SAMs with alternative organic cores that may possess specific benefits. In this study, three novel SAMs are incorporated in p-i-n perovskite solar cells, each based on an aromatic core commonly used in organic semiconductors. The novel SAMs vary in their energy level alignment with the perovskite active layer. Optimal alignment is achieved with a pyrene-based SAM (4PAPyr), resulting in solar cells that outperform the commercially available 2PACz. Moreover, due to improved surface coverage, the use of 4PAPyr leads to a significantly higher number of working solar cell devices when compared to 2PACz, which is of particular interest with regard to upscaling. After device optimization, a power conversion efficiency of 22.2% is achieved with 4PAPyr. This research underlines the importance of diversifying SAMs to unlock further advancements in perovskite solar cell efficiency and scalability.

In this work, effective p-type doping strategies for the representative crystalline polymer P3HT are explored to achieve efficient and stable PSCs. According to the Hard–Soft-Acid–Base theory, the soft base P3HT is more likely to form a stable Lewis acid–base adduct with the reactive soft acid radical, resulting in a strong charge-transfer interaction, thereby improving the doping efficiency.

Abstract

Perovskite solar cells (PSCs) have significant potential for next-generation photovoltaic technology applications. However, the instability of hole transport layers (HTLs) becomes the major obstacle to long-term operational devices, which are affected by the intrinsic thermal instability and loose structure of hole transport materials, as well as the hygroscopicity and migration of dopants. Here, poly(3-hexylthiophene-2,5-diyl) (P3HT) is used as a model crystalline polymer to thoroughly investigate effective p-type doping strategies and the underlying mechanism. According to Hard–Soft-Acid–Base theory, the soft base P3HT is more likely to form a stable Lewis acid–base adduct with the reactive soft acid radical, resulting in a strong charge-transfer interaction, thereby enhancing conductivity and regulating the energy band of the HTL. Meanwhile, the radical cation salt can promote pre-nucleation to optimize the crystallization orientation of P3HT. The resulting PSCs exhibited the efficiency of 25.16%, which is the highest efficiency reported so far based on doped P3HT. In addition, the resulting devices demonstrated excellent stability, maintaining 96.5%, 96%, and 91% of their initial efficiency after aging under continuous illumination for 2028 h, at 85 °C for 1080 h, and at maximum power point (MPP) tracking under continuous 1 Sun illumination at 85 °C for 528 h, respectively.

A vapor-to-solid deposition of high-quality large-area perovskite films is developed via a new process based on a 2D intermediated phase. Efficiencies of 21.1% and 20.1% are achieved for perovskite modules with active areas of 12.5 and 48.0 cm², respectively.

Abstract

Perovskite solar cells (PSCs) can enable renewable electricity generation at low levelized costs, subject to the invention of an economically feasible technology for their large-scale fabrication, like vapor deposition. This approach is effective for the fabrication of small area (<1 cm²) PSCs, but its scale-up to produce high-efficiency larger area modules has been limited by a severe imbalance between the vapor-solid reaction kinetics and the mass-transport of the volatile ammonium salt precursor. In this study, an amidine-based low-dimensional perovskite is introduced as an intermediate of the solid-vapor reaction to help resolve this limitation. This improves reaction pathway produces unique vertically monolithic grains with no detectable horizontal boundaries, which is used to produce 1.0 cm² PSCs with an efficiency of 22.1%, as well as 12.5 and 48 cm² modules delivering 21.1% and 20.1% efficiency, respectively. The modules retain ≈85% of their initial performance after 900 h of continuous operation (ISOS-L-1 protocol) and ≈100% after 2800 h of storage in an ambient environment (ISOS-D-1 protocol).

A bottom-up, all-in-one modification strategy is proposed by introducing a multisite antioxidant ergothioneine (EGT) at the buried interface to manage iodide ions and manipulate crystallization dynamics. The EGT-optimization firmly anchors I⁻ and inhibits their oxidation to I₂. The optimized all-air processed device achieves a remarkable PCE of 25.13%, which is among the highest values reported for devices fabricated in air.

Abstract

Halide-related defects at the buried interface not only cause nonradiative recombination, but also seriously impair the long-term stability of perovskite solar cells (PSCs). Herein, a bottom-up, all-in-one modification strategy is proposed by introducing a multisite antioxidant ergothioneine (EGT) at the buried interface to manage iodide ions and manipulate crystallization dynamics. The findings demonstrate that EGT not only passivates uncoordinated Sn⁴⁺/Pb²⁺ defects, but also firmly anchors iodide ions and inhibits their oxidation to I₂. Additionally, the modification by EGT enhances the oriented crystallization of perovskite, improves the carrier dynamics, and releases residual stresses. Consequently, the optimized all-air processed device (Rb_0.02(FA_0.95Cs_0.05)_0.98PbI_2.91Br_0.03Cl_0.06) achieves a remarkable power conversion efficiency (PCE) of 25.13%, which is among the highest values reported for devices fabricated in air, along with ultrahigh open-circuit voltage (V _OC) of 1.191 V and fill factor (FF) of 84.9%. The optimized device without encapsulation exhibits strong humidity, thermal, and operational stability under ISOS protocol. Specifically, the initial efficiency of the device is retained at 90.12% after 1512 h of thermal ageing at 65 °C and 90.14% after 930 h of continuous maximum power point tracking (MPPT) under simulated AM1.5 illumination.