Stable Perovskite Solar Cells Research Articles

Charge Dynamics and Defect States under “Spot‐Light”: Spectroscopic Insights into Halide Perovskite Solar Cells

Halide perovskite solar cells (PSCs) have shown remarkable power conversion efficiencies. However, the inherent defect issues of perovskite materials still limit their performance and long‐term stability, resulting in lifespans far from commercial standards. With their noninvasive approach to probing the electronic and vibrational properties of materials, spectroscopic techniques have become crucial tools for uncovering and understanding defect states and complex charge carrier dynamics in halide perovskites. This review explores the application of various advanced spectroscopic techniques in PSCs to elucidate the complex behaviors of charge carriers within PSCs. These techniques reveal detailed temporal and spatial distributions of charge carriers, enabling precise analysis of defect impacts and interfacial charge transfer processes. By integrating spectroscopic data, it is possible to more accurately identify and mitigate defect‐induced nonradiative recombination and charge transfer, thereby enhancing the stability and efficiency of PSCs. This comprehensive spectroscopic understanding is crucial for developing innovative technologies to accelerate the commercial viability of PSCs.

Chalcogenides in Perovskite Solar Cells with a Carbon Electrode: State of the Art and Future Prospects

Perovskite solar cells (PSCs) have been on the forefront of advanced research for over a decade, achieving constantly increasing power conversion efficiencies (PCEs), while their route towards commercialization is currently under intensive progress. Towards this target, there has been a turn to PSCs that employ a carbon electrode (C-PSCs) for the elimination of metal back contacts, which increase the cost of corresponding devices while at the same time have a severe impact on their stability. Chalcogenides are chemical compounds that contain at least one chalcogen element, typically sulfur (S), selenium (Se), or tellurium (Te), combined with one metallic element. They possess semiconducting properties and have been proven to have beneficial effects when incorporated in a variety of solar cell types, including dye sensitized solar cells (DSSCs), quantum dot sensitized solar cells (QDSSCs), and Organic Solar Cells (OSCs), either as interlayers or added in the active layers. Currently, an increasing number of studies have highlighted their potential for achieving high-performing and stable PSCs. In this review, the most promising results of the latest studies regarding the implementation of chalcogenides in PSCs with a carbon electrode are presented and discussed, merging two research trends that are currently on the spotlight of solar cell technology.

Triphenylamine-Functionalized Metal Nanoclusters for Efficient and Stable Perovskite Solar Cells.

Reported herein is a ligand engineering strategy to develop photoelectric active metal nanoclusters (NCs) with atomic precision. Triphenylamine (TPA), a typical organic molecule in the photoelectric field, is introduced for the first time to prepare atomically precise metal NCs that prove effective in the fabrication of perovskite solar cells (PSCs). The scalable synthetic prototype, unique electronic strucuture, and atomically precise structure of the cluster ([(AgCu)37(PPh3)8(TPA-C≡C)24]5+) are illustrated in this work. When being employed as a buffer layer in the perovskite/HTL interface of PSCs, significantly enhanced performance is observed. The resultant n-i-p devices achieved a substantial power conversion efficiency as high as 25.1% and long-term stability. The findings offer valuable insights into preparing functionalized metal NCs that play multiple roles in improving the performance of the device: while the inorganic metal core enhances conductivity, the organic TPA shell promotes the "carrier transfer" between the perovskite and HTL layer and prevents the perovskite from corrosion.

Hexafluoroisopropanol modified MXene for perovskite surface remodeling and interfacial dipole effect enhancement

The development of high-efficiency and stable perovskite (PVK) solar cells (PSCs) still faces the challenge of non-ideal interfaces between PVK and charge transport layers. Herein, the hexafluoroisopropanol (HFIP) modified two-dimensional Ti3C2Tx MXene is custom-made (MX-HFIP) and employed as the interlayer between the PVK and hole transport layer (HTL) interface by forming hydrogen bonds. The MX-HFIP serves to reinforce the interface contact and remodel the surface of PVK, leading to a high-quality PVK film with a significantly reduced defect density, suppressed nonradiative recombination, and inhibited invasion of water and oxygen. Moreover, the synergistic effect of MXene and HFIP results in an enhanced interfacial dipole effect and an optimized energy-level alignment, thereby increasing the driving force for charge extraction and transport at the PVK/HTL interface. Therefore, the MX-HFIP treated PSC achieves a substantially-enhanced power conversion efficiency (PCE) of 22.33 %, as compared to 20.05 % of the untreated device. Besides, the MX-HFIP treated PSC delivers significantly enhanced stabilities, with 88 % of its initial PCE after 1656 h of storage at 25 °C under 30 %⁓40 % relative humidity. These findings demonstrate the advancement using fluorine-rich molecule modified MXene to improve interfacial properties for enhancing performances and stabilities of optoelectronic devices.

Surface Planarization-Epitaxial Growth Enables Uniform 2D/3D Heterojunctions for Efficient and Stable Perovskite Solar Modules.

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 1.55eV. To demonstrate the universality of the strategy applied for different perovskites, the champion device based on a 1.57eV 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 1246h operational tracking under 65 °C (ISOS-L-3 protocol) and 91.1% after 862h under the ISOS-O-1 protocol.

Simultaneous Suppression of Multilayer Ion Migration via Molecular Complexation Strategy toward High‐Performance Regular Perovskite Solar Cells

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.

Simultaneous Suppression of Multilayer Ion Migration via Molecular Complexation Strategy toward High-Performance Regular Perovskite Solar Cells.

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.

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 butylammonium cation as an additive to enhance the performance of PSCs. By incorporating 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.

Dual-Site Crystallization Regulation for Highly Efficient and Stable Perovskite Solar Cells

Dual-Site Crystallization Regulation for Highly Efficient and Stable Perovskite Solar Cells

Dielectric screening modulating charge carrier recombination in high-performance of CsPbI2Br carbon-based perovskite solar cells

As a type of ionic crystal, CsPbI2Br perovskite inevitably generates a significant number of defects during the rapid crystallization process that occurs from deposition to annealing. The non-radiative recombination of charge carriers caused by these defects severely limits the performance of perovskite solar cells (PSCs). Here, 2,2,2-trifluoroethylamine hydrochloride (F3EACl) with permanent dipole moment is devised to modify the perovskite interface. Highly electronegative trifluoro groups can accelerate the dielectric response of perovskite films, intensify the dielectric screening effect, and significantly suppress non-radiative recombination of charge carriers. Meanwhile, the –NH3+ group in F3EACl effectively passivates the defects at the perovskite surface, further alleviating the defect-induced carrier recombination loss. Consequently, the CsPbI2Br carbon-based PSCs treated with F3EACl achieved an impressive power conversion efficiency (PCE) of 14.69 % at a higher open-circuit voltage (1.28 V), along with excellent environmental stability. This work demonstrates a unique tactic to achieve efficient and stable PSCs by modulating charge carrier recombination utilizing the synergistic effects of dielectric screening and defect passivation.

Composition design of fullerene-based hybrid electron transport layer for efficient and stable wide-bandgap perovskite solar cells

Composition design of fullerene-based hybrid electron transport layer for efficient and stable wide-bandgap perovskite solar cells

Design, Exploitation, and Rational Improvements of Diazirine-Based Universal Polymer Crosslinkers.

ConspectusAddition of new covalent bonds between the chains of thermoplastic polymers (i.e., crosslinking) provides improved mechanical strength and enhanced high-temperature performance while also providing an effective strategy for photopatterning. Traditionally, however, crosslinking of each polymer substrate has required the use of a specific crosslinking technology (hydrosilylation for PDMS, vulcanization for rubber, etc.). The lack of a general solution to the challenge of polymer crosslinking means that there are many thermoplastics (e.g., polypropylene or polyhydroxyalkanoates) that have desirable properties, but which cannot be upgraded by traditional crosslinking technologies.Our lab developed the first universal crosslinkers for aliphatic polymers by leveraging trifluoromethyl aryl diazirine motifs, functional groups that have been widely used in chemical biology for >30 years, but which have seldom been exploited in materials science. These novel reagents work (via C-H insertion) on essentially any commodity polymer that contains aliphatic C-H bonds, including industrial plastics like polypropylene (the crosslinking of which has been an outstanding challenge in the field for >50 years), as well as commercially important elastomers (e.g., polydimethylsiloxane), biodegradable polymers (e.g., polycaprolactone), and green polymer materials derived from biomass (e.g., polyhydroxyalkanoates).Subsequent structure-function work from our group led to crosslinkers that were >10-fold more effective in undergoing C-H insertion with aliphatic substrates. We then developed an improved synthesis of our electronically optimized diazirines and incorporated them into a family of cleavable crosslinker reagents, which permit the on-demand generation of reprocessable thermosets. At the same time, other groups replaced the perfluoropropyl linker in our first-generation crosslinker with a series of dynamic linkages; these permit the ready generation of vitrimeric materials and can be used in the reactive compatibilization of immiscible plastic waste.Since the publication of our initial Science paper in 2019, this burgeoning field of diazirine-based polymer crosslinkers has experienced an explosion of interest. Publications from our lab and others have described the use of these reagents in covalent adhesion, photopatterning of low dielectric materials for microelectronics, and direct optical printing of quantum dots. Our crosslinkers have also been shown to heighten the robustness of ice-phobic coatings and improve the performance of woven ballistic fabric, while─perhaps most unexpectedly─substantially improving the stability of high-performance perovskite solar cells. Electronically optimized diazirines can also be used to covalently link proteins to polymer surfaces, suggesting a broad range of applications in the biocompatibilization of medical devices. This Account will summarize the development of trifluoromethyl aryl diazirine reagents for materials science over the past 5 years. A brief comparison will also be made, in the Summary and Outlook section at the end of the Account, to competing (and often complementary) reagents based upon azide and diazoalkyl motifs. Finally, we have compiled a Frequently Asked Questions list that covers many practical aspects of crosslinker design and application; this is appended as Supporting Information.

Ion-Mediated Molecular Bridging at Buried Interface Enhances Perovskite Solar Cell Durability.

Engineering heterointerfaces via molecular bridging has been crucial for achieving perovskite solar cells (PSCs) featuring optimal power conversion efficiencies (PCEs) and environmental durability. However, the challenge remains in ensuring interfacial mechanical reliability to enhance the long-term durability of PSCs. Herein, an ion-mediated molecular bridging strategy is intentionally exploited to improve the mechanical integrity between the perovskite bottom and electron-transport layers (ETLs) through balancing interfacial toughness and strength. As a demonstration of the concept, a zwitterionic guanylurea phosphate additive is preburied onto the SnO2 ETL, in which the guanylurea with bifacial NH2 groups servers as a molecular bridge connecting the perovskite and ETL through electrostatic coupling, while the phosphate can interact with charged species at the heterointerface to strengthen the mechanical contact. Benefiting from the robust heterointerfaces, the mechanical durability of flexible PSCs is significantly enhanced, retaining 91.3% of the original efficiency following 6000 bending cycles (bending radius = 3 mm). Additionally, the enhanced mechanical integrity at the buried interface also benefits the charge transfer and chemical stability in rigid PSCs, contributing to PCEs of over 25% as well as thermal stability with T86 of 1200 h under aging at 85 °C.

Metal–Organic Frameworks and Derivative Materials in Perovskite Solar Cells: Recent Advances, Emerging Trends, and Perspectives

The power conversion efficiency (PCE) of perovskite solar cells (PSCs) has reached an impressive value of 26.1%. While several initiatives such as structural modification and fabrication techniques helped steadily increase the PCE and stability of PSCs in recent years, the incorporation of metal–organic frameworks (MOFs) in PSCs stands out among other innovations and has emerged as a promising path forward to make this technology the front‐runner for realizing next‐generation low‐cost photovoltaic technologies. Owing to their unique physiochemical properties and extraordinary advantages such as large specific surface area and tunable pore structures, incorporating them as/in different functional layers of PSCs endows the devices with extraordinary optoelectronic properties. This article reviews the latest research practices adapted in integrating MOFs and derivative materials into the constituent blocks of PSCs such as photoactive perovskite absorber, electron‐transport layer, hole‐transport layer, and interfacial layer. Notably, a special emphasis is placed on the aspect of stability improvement in PSCs by incorporating MOFs and derivative materials. Also, the potential of MOFs as lead absorbents in PSCs is highlighted. Finally, an outlook on the critical challenges faced and future perspectives for employing MOFs in PSCs in light of the commercialization of PSCs is provided.

Small Molecular Dibenzo[b,d]thiophene-Based Hole Transport Materials for Tin-Lead Perovskite Solar Cell.

The most commonly used hole transport material (HTM) in tin-lead (Sn-Pb) perovskite solar cells (PSCs) is the aqueous poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS), and its inherent hygroscopic and acidic features greatly limit the power conversion efficiency (PCE) and stability of PSCs. Concerning this, by selecting dibenzo[b,d]thiophene 5,5-dioxide (DBTDO) as the core and engineering the donor units, 4-methoxy-N-(4-methoxyphenyl)-N-phenylaniline (TPA) and N1-(4-(bis(4-methoxyphenyl)amino)phenyl)-N4,N4-bis(4-methoxyphenyl)benzene-1,4-diamine (DTPA) as peripheral groups, two alternative HTMs are reported. Among them, the HTM TPA-DBTDO-DTPA can form a smoother film, which is conducive to the growth of dense perovskite film on it and shows the most suitable energy level. Meanwhile, the sulfonyl unit can passivate the buried defects of perovskite and improve the open-circuit voltage (VOC) of Sn-Pb mixed PSCs. Correspondingly, the TPA-DBTDO-DTPA-based PSC achieves a champion power conversion efficiency of 22.6% and maintains 75.9% of the initial PCE after aging 1000 h in a nitrogen (N2) environment, which fully outperforms the PEDOT:PSS-based control device.

PTAA‐infiltrated thin‐walled carbon nanotube electrode with hidden encapsulation for perovskite solar cells

AbstractIn perovskite solar cells (PSCs), expensive gold or silver metal has traditionally been utilized as the rear electrode for highly efficient performance. In this context, carbon nanotube (CNT) electrodes have been considered promising rear electrodes because of their excellent electrical conductivity, mechanical strength, and chemical stability in PSCs. Despite these favorable characteristics, concerns have been raised about the power conversion efficiency (PCE) and stability of PSCs based on CNTs due to the porosity of CNT electrodes. In this study, we employed both poly(triarylamine) (PTAA) infiltration and rear electrode hidden encapsulation approaches to address issues related to the porosity of thin‐walled carbon nanotube (TWCNT) electrodes to achieve high efficiency and stability. The infiltration of low‐molecular‐weight PTAA into the TWCNT electrode reduced electrode porosity while simultaneously improving the interfacial contact of the TWCNT layer with the perovskite layer. Furthermore, a novel encapsulation design was employed to prevent air and water exposure of the TWCNT electrode, which significantly enhanced device stability. PSCs with TWCNT rear electrodes developed on the basis of these strategies have the best PCE of 19.5% and show long‐term stability, retaining 96% and 74% of the initial PCE after 225 h at maximum power point tracking under AM 1.5G illumination and 916 h at 85°C/85% relative humidity, respectively.image

Solution‐Processed Multifunctional Thin‐Film Encapsulation of Perovskite Thin Films and Devices

Herein, the effect of multicomponent composite encapsulation on the stability of perovskite thin films and perovskite solar cells, as well as lead leakage upon water immersion, is investigated. The encapsulation is simple and low cost since it is entirely deposited by solution processed techniques in the ambient atmosphere. It consists of a spray‐coated composite layer sandwiched between two spin‐coated layers. The composite layer contains hygroscopic nanomaterials, oxygen scavengers, and lead adsorbing nanomaterials, which enables reduced lead leakage and improved stability of encapsulated perovskite during storage in ambient, immersion in water, as well as illumination in dry air. The encapsulation layers show high transmittance and did not have a significant effect on the short‐circuit current density and open‐circuit voltage despite the deposition of encapsulation in ambient air. The encapsulated devices retain 80% of their initial performance after 4 h of immersion in water.

Methodologies to Improve the Stability of High-Efficiency Perovskite Solar Cells

Methodologies to Improve the Stability of High-Efficiency Perovskite Solar Cells

A Multisite Atomic‐Oxygen Anchoring Strategy Affords Efficient and Stable Perovskite Solar Cells

AbstractLewis 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.

Leveraging Phenazine‐Based Ligands for Optimized Perovskite Optoelectronic Performance Through Chelation and Redox Engineering

AbstractPerovskite nanocrystals (PNCs) hold immense potential for optoelectronic and photovoltaic applications. However, their performance is hindered by surface defects that promote non‐radiative recombination and reduce stability. Surface engineering, particularly through defect passivation, is crucial for achieving high‐performing perovskite solar cells. Chelation has been shown to significantly improve the efficiency and stability of perovskite solar cells. In this study, a novel chelation strategy using 1,10‐Phenanthroline (Phen) is presented as a bidentate chelating ligand to effectively target and passivate these detrimental surface defects. By strategically designing a Phenanthroline derivative, dipyrido[3,2‐a:2′,3′‐c]phenazin‐11‐amine (Phen‐derivative) with optimized redox potentials, dual functionality: efficient defect passivation and hole transport is achieved. X‐ray photoelectron spectroscopy (XPS) confirms the superior binding capability of the Phen‐derivative due to chelation. This strong interaction facilitates efficient and ultrafast charge transfer from PNCs and the formation of a long‐lived charge‐separated state, as evidenced by sustained bleaching in transient absorption spectra. A metal‐dipyrido[3,2‐a:2′,3′‐c]phenazin‐11‐amine complex (Ir‐complex) derived from dipyrido[3,2‐a:2′,3′‐c]phenazin‐11‐amine, but lacking a chelation site, hinders desired hole transfer despite similar charge transfer energetics. This work emphasizes the critical role of chelation‐mediated interfacial interactions and energy alignment in designing effective charge shuttle molecules and unlocking the potential of lead‐chelating hole transporters for next‐generation light‐harvesting technologies.