JIALINGBO

In situ cyclized polyacrylonitrile (CPAN) is developed as an electron selective layer (ESL) for highly efficient and stable n-i-p PSCs. The CPAN layer possesses n-type semiconductor properties with a high electron mobility of 4.13×10⁻³ cm² V⁻¹ s⁻¹, and is insoluble in common solvents. The resultant PSC affords a power conversion efficiency of 23.12 % with high operational stability.

Abstract

In situ cyclized polyacrylonitrile (CPAN) is developed to replace n-type metal oxide semiconductors (TiO₂ or SnO₂) as an electron selective layer (ESL) for highly efficient and stable n-i-p perovskite solar cells (PSCs). The CPAN layer is fabricated via facile in situ cyclization reaction of polyacrylonitrile (PAN) coated on a conducting glass substrate. The CPAN layer is robust and insoluble in common solvents, and possesses n-type semiconductor properties with a high electron mobility of 4.13×10⁻³ cm² V⁻¹ s⁻¹. With the CPAN as an ESL, the PSC affords a power conversion efficiency (PCE) of 23.12 %, which is the highest for the n-i-p PSCs with organic ESLs. Moreover, the device with the CPAN layer holds superior operational stability, maintaining over 90 % of their initial efficiency after 500 h continuous light soaking. These results confirm that the CPAN layer would be a desirable low-cost and efficient ESL for n-i-p PSCs and other photoelectronic devices with high performance and stability.

Interface-induced nonradiative recombination losses are significantly limiting the performance improvement in perovskite solar cells (PSCs). A multifunctional dipole molecule modifies the perovskite surface to reduce defects and optimize energy alignment, suppressing the nonradiative recombination. The p-i-n device achieves an improved efficiency that stabilizes under both high humidity and maximum power point tracking.

Abstract

Interface-induced nonradiative recombination losses at the perovskite/electron transport layer (ETL) are an impediment to improving the efficiency and stability of inverted (p-i-n) perovskite solar cells (PSCs). Tridecafluorohexane-1-sulfonic acid potassium (TFHSP) is employed as a multifunctional dipole molecule to modify the perovskite surface. The solid coordination and hydrogen bonding efficiently passivate the surface defects, thereby reducing nonradiative recombination. The induced positive dipole layer between the perovskite and ETLs improves the energy band alignment, enhancing interface charge extraction. Additionally, the strong interaction between TFHSP and the perovskite stabilizes the perovskite surface, while the hydrophobic fluorinated moieties prevent the ingress of water and oxygen, enhancing the device stability. The resultant devices achieve a power conversion efficiency (PCE) of 24.6%. The unencapsulated devices retain 91% of their initial efficiency after 1000 h in air with 60% relative humidity, and 95% after 500 h under maximum power point (MPP) tracking at 35 °C. The utilization of multifunctional dipole molecules opens new avenues for high-performance and long-term stable perovskite devices.

In this work, through various characterizations, we reveal that photoinduced iodine escape is the trigger for halide phase segregation in wide-bandgap perovskites and design an organic additive AIDCN accordingly, which effectively suppresses the segregation. As a result, the photovoltaic performance of wide-bandgap perovskites is enhanced, and we realize a record-high efficiency for perovskite-organic tandem solar cells. Our findings shed light on understanding the mechanism of halide phase segregation and pave the way for further development of perovskite-organic tandem cells.

A framework based on thickness-dependent time-resolved photoluminescence spectroscopy is provided that allows bulk and surface lifetimes to be separated. The analysis is extended to calculate the surface recombination velocities of 18 contacts under standard and inverted configurations. The resolved implied open-circuit voltages of three devices are predicted using this framework, and compared with fully fabricated cells. With this analysis, it is shown that C₆₀ accounts for ≈90% of all recombination, while bulk losses are minimal in perovskite solar cells.

Abstract

Perovskite solar cells have reached an impressive certified efficiency of 26.1%, with a considerable fraction of the remaining losses attributed to carrier recombination at perovskite interfaces. This work demonstrates how time-resolved photoluminescence spectroscopy (TRPL) can be utilized to locate and quantify remaining recombination losses in perovskite solar cells, analogous to methods established to improve silicon solar cell passivation and contact layers. It is shown how TRPL analysis can be extended to determine the bulk and surface lifetimes, surface recombination velocity, the recombination parameter, J₀ , and the implied open-circuit voltage (iV_oc ) of any perovskite device configuration. This framework is used to compare 18 carrier-selective and passivating contacts commonly used or emerging for perovskite photovoltaics. Furthermore, the iV_oc values calculated from the TRPL-based framework are directly compared to those calculated from photoluminescence quantum yields and the measured solar cell V_oc . This simple technique serves as a practical guide for screening and selecting multifunctional, passivating perovskite contact layers. As with silicon solar cells, most of the material and interface analysis can be done without fabricating full devices or measuring efficiency. These purely optical measurements are even preferable when studying bulk and interfacial passivation approaches, since they remove complicating effects from poor carrier extraction.

The P3HT hole transport layer (HTL) featuring preferable three-dimension molecular orientation is realized via optimizing its preparation process. The preferable molecular orientation of P3HT HTL imparts improved electronic properties, enhanced moisture-repelling capability, intensified defect passivation, and matched energy level. The small-area (0.04 cm²) and large-area (1 cm²) carbon-electrode devices deliver notable efficiency of 20.55% and 18.32% with desirable stability.

Abstract

Carbon-based perovskite solar cells (PSCs) coupled with solution-processed hole transport layers (HTLs) have shown potential owing to their combination of low cost and high performance. However, the commonly used poly(3-hexylthiophene) (P3HT) semicrystalline-polymer HTL dominantly shows edge-on molecular orientation, in which the alkyl side chains directly contact the perovskite layer, resulting in an electronically poor contact at the perovskite/P3HT interface. The study adopts a synergetic strategy comprising of additive and solvent engineering to transfer the edge-on molecular orientation of P3HT HTL into 3D molecular orientation. The target P3HT HTL possesses improved charge transport as well as enhanced moisture-repelling capability. Moreover, energy level alignment between target P3HT HTL and perovskite layer is realized. As a result, the champion devices with small (0.04 cm²) and larger areas (1 cm²) deliver notable efficiencies of 20.55% and 18.32%, respectively, which are among the highest efficiency of carbon-electrode PSCs.

Nature, Published online: 26 June 2024; doi:10.1038/s41586-024-07723-3

Buried interface molecular hybrid for inverted perovskite solar cells

A triple halide composition, additive- and methylammonium-free, fabricates wide-bandgap perovskites (1.64 eV). Small amounts of chloride prevent photoinduced halide segregation and improve the crystallization process significantly, enhancing open-circuit voltages (1.23 V). These characteristics are introduced for the first time in a p-i-n single-junction configuration employing a self-assembled monolayer. Devices achieve up to 22.6% photoconversion efficiencies with exceptional stability at 85 °C.

Abstract

Developing efficient wide-bandgap perovskites is critical to exploit the benefits of a multi-absorber solar cell and engineering commercially attractive tandem solar cells. Here, a robust, additive-free, methylammonium-free triple halide composition for the fabrication of close-to-ideal wide-bandgap perovskites (1.64 eV) is reported. The introduction of low percentages of chloride into the perovskite layer avoided photoinduced halide segregation and lead to an evident improvement in the crystallization process, reaching enhanced open-circuit voltages as high as 1.23 V. A perovskite of these characteristics is introduced for the first time in a p-i-n single-junction configuration using a self-assembled monolayer, with devices achieving photoconversion efficiencies of up to 22.6% with ultra-high stability, retaining ≈80% of their initial efficiency after >1000 h of continuous operation unencapsulated in a nitrogen atmosphere at 85 °C. This result paves the way toward highly efficient multi-junction tandem solar cells, bringing perovskite technology closer to commercialization.

This study provides guidelines for the use of efficient ETMs in PSCs, describes the remarkable progress of ETMs in various perovskite systems, and focuses on the key ETL challenges: regulating grain structure, defect passivation techniques, energy level alignment, and interface engineering. It finishes with a detailed assessment of the most advanced ETMs, focusing on their strategic importance and future challenges.

Abstract

Perovskite solar cells (PSCs) stand at the forefront of photovoltaic research, with current efficiencies surpassing 26.1%. This review critically examines the role of electron transport materials (ETMs) in enhancing the performance and longevity of PSCs. It presents an integrated overview of recent advancements in ETMs, like TiO₂, ZnO, SnO₂, fullerenes, non-fullerene polymers, and small molecules. Critical challenges are regulated grain structure, defect passivation techniques, energy level alignment, and interfacial engineering. Furthermore, the review highlights innovative materials that promise to redefine charge transport in PSCs. A detailed comparison of state-of-the-art ETMs elucidates their effectiveness in different perovskite systems. This review endeavors to inform the strategic enhancement and development of n-type electron transport layers (ETLs), delineating a pathway toward the realization of PSCs with superior efficiency and stability for potential commercial deployment.

In this communication, we report two novel intrinsically liquid crystalline metal halide perovskite-like materials by utilizing fluorinated ionic liquid crystalline (FILC) mesogens based on polyfluorinated alkylimidazolium cations. Manifold intermolecular F ⋅ ⋅ ⋅ F interactions were found to be essential for the solid- and liquid-crystalline orders of the perovskite-like structures. This study may pave the way towards a new class of perovskite-based soft materials.

Abstract

Hybrid Organic-Inorganic Halide Perovskites (HOIHPs) represent an emerging class of semiconducting materials, widely employed in a variety of optoelectronic applications. Despite their skyrocket growth in the last decade, a detailed understanding on their structure–property relationships is still missing. In this communication, we report two unprecedented perovskite-like materials based on polyfluorinated imidazolium cations. The two materials show thermotropic liquid crystalline behavior resulting in the emergence of stable mesophases. The manifold intermolecular F ⋅ ⋅ ⋅ F interactions are shown to be meaningful for the stabilization of both the solid- and liquid-crystalline orders of these perovskite-like materials. Moreover, the structure of the incorporated imidazolium cation was found to tune the properties of the liquid crystalline phase. Collectively, these results may pave the way for the design of a new class of halide perovskite-based soft materials.

The ─NH₂ group of BAMPy reacts with FA⁺ to occupy A site of perovskite crystal framework, enhancing binding energy of ambient moisture with perovskites and thus relieving moisture interference on perovskite crystallization and structural homogeneity. The targeted PSCs fabricated under full-air conditions deliver the efficiency of 24.11% with exceptional operational stability.

Abstract

The fabrication of perovskite solar cells (PSCs) under full-air conditions accelerates their scalable production and industrialization. However, ambient moisture interacts with perovskites during the film formation that disturbs their crystallization and triggers structural imperfections. Here, a formamidine (FA) active addition reaction (FAAR) strategy is devised to intercept the deleterious chemical coordination. The simultaneous incorporation of 2, 6-bis(aminomethyl)pyridine (BAMPy) molecule into tin oxide surface and perovskite bulk ameliorates the interface contact and film interior. It is found that the tail amino group from BAMPy selectively reacts with FA cation, occupying A site of perovskite crystals, increasing binding energy of perovskite with H₂O molecule even in a defective surface, thereby strengthening moisture tolerance. This strategy effectively modifies perovskite crystallization in ambient air, favors structural uniformity, and forms the compressive-strained films. The FAAR-modified PSC devices fabricated under full-air conditions deliver the highest efficiencies of 24.11% and 21.68% with aperture areas of 0.06 and 1 cm², respectively. The favorable moisture impediment property contributes to perovskite crystallization enhancement and structural uniformity, maintaining 90.8% of their initial performance for the encapsulated devices after 2400 h storage under accelerating damp-heat measurements (85 °C and 85% relative humidity).

A unique nanostructure of elevated hole transport layer between the perovskite grains is introduced to effectively inhibit ion migration in perovskite light-emitting diodes, achieving a record operational half-lifetime of 256 and 1774 h under current densities of 100 and 20 mA cm⁻²， respectively.

Abstract

Ion migration is a major factor affecting the long term stability of perovskite light-emitting diodes (LEDs), which limits their commercialization potential. The accumulation of excess halide ions at the grain boundaries of perovskite films is a primary cause of ion migration in these devices. Here, it is demonstrated that the channels of ion migrations can be effectively impeded by elevating the hole transport layer between the perovskite grain boundaries, resulting in highly stable perovskite LEDs. The unique structure is achieved by reducing the wettability of the perovskites, which prevents infiltration of the upper hole-transporting layer into the spaces of perovskite grain boundaries. Consequently, nanosized gaps are formed between the excess halide ions and the hole transport layer, effectively suppressing ion migration. With this structure, perovskite LEDs with operational half-lifetimes of 256 and 1774 h under current densities of 100 and 20 mA cm⁻² respectively are achieved. These lifetimes surpass those of organic LEDs at high brightness. It is further found that this approach can be extended to various perovskite LEDs, showing great promise for promoting perovskite LEDs toward commercial applications.

Al₂O₃ deposited via atomic layer deposition improves power conversion efficiency, moisture resistance, and long-term stability of formamidinium-cesium perovskite solar cells. 1 nm-thick passivation layer improves fill factor and open-circuit voltage, while 30 nm-thick capping layer acts as an efficient moisture barrier layer. Results from more than 300 devices show significantly improved maximum power point stability, especially under cyclic illumination.

Improving the power conversion efficiency (PCE) and stability of perovskite solar cells (PSCs) remain the two most important goals of perovskite research. Herein, the effects of Al₂O₃ interlayer on the performance of formamidinium-cesiums and “triple cation” PSCs by depositing a thin Al₂O₃ layer via atomic layer deposition on different interfaces are analyzed. It is found that it can efficiently serve as a passivation layer of perovskite absorber, as a seed layer for the compact growth of the subsequent SnO₂ layer, or as a capping layer to the whole cell in the superstrate configuration to prevent moisture ingress. The optimized devices utilizing Al₂O₃ have on average more than 1% absolute higher PCE, with reduced penetration of moisture inside the device. Especially, the capping layer has shown the greatest benefit, extending the stability of the devices by more than two times and allowing long-term operation without encapsulation. In the best case, a T₈₀ time of almost 900 h under day/night-cycling illumination is obtained. The observed trends are based on data from a large number of devices (more than 300 devices were tested in the maximum power point), which give statistical relevance to the promising results.

A facile strategy is reported to systematically manipulate the crystallization and passivate defects by incorporating robust dual-functional additives. The additive not only regulates crystallization kinetics but acts as a passivator, effectively passivating defects, releasing residual strain, and achieving a favorable n-type contact interface. The resultant devices accomplish a power conversion efficiency (PCE) of 24.05% and an ultra-high fill factor (FF) of 84.22% with improved stability.

Abstract

Inverted perovskite solar cells (PSCs) comprising formamidinium-cesium (FA-Cs) lead triiodide have garnered considerable attention due to their impressive efficiency and remarkable stability. Nevertheless, synthesizing high-quality FA-Cs alloyed perovskite films presents challenges, primarily attributable to the intricate interphase process involved and the absence of methylammonium (MA⁺) and mixed halogens. Here, the additive 3-phosphonopropanoic acid (3-PPA) is introduced, with bifunctional phosphonic acid groups, into the perovskite precursor to modulate the crystal growth and provide passivation at grain boundaries. In situ characterization reveals that the 3-PPA can form a “rapid nucleation, slow growth” mechanism, resulting in perovskite films with enlarged grains and enhanced crystallinity. In addition, 3-PPA serves to passivate grain boundary defects and release residual strain by forming molecular bridging, leading to the passivated films achieving a fluorescence lifetime of 5.79 microseconds with a favorable n-type contact interface. As a result, the resulting devices incorporating 3-PPA achieve a champion power conversion efficiency (PCE) of 24.05% and an ultra-high fill factor (FF) of 84.22%. More importantly, the optimized devices exhibit satisfactory stability under various testing conditions. The findings underscore the pivotal role of multifunctional additives in crystallization control and defect passivation for high-performance MA-free and pure iodine PSCs.

A mixed-SAM strategy (Mx-SAM) is proposed to enhance the adsorption energy of SAMs on the ITO surface, facilitate the formation of dense and humidity-resistant hole-selective layer (HSL) on substrates, the wide-bandgap (1.68 eV) PSCs achieved a PCE of 22.63%, and the fabricated industrially-compatible P/S-TSCs through antisolvent-assisted crystallization strategies achieve a remarkable efficiency of 28.07%.

Abstract

The antisolvent-assisted spin-coating still lags behind the thermal evaporation method in fabricating perovskite films atop industrially textured silicon wafers in making monolithic perovskite/silicon solar cells (P/S-TSCs). The inhomogeneity of hole-selective self-assembled monolayers (SAMs) often arises from the insufficient bonding between hygroscopic phosphonic acid anchors and metal oxide. To address this, a mixed-SAM strategy (Mx-SAM) is proposed to enhance the adsorption energy of SAMs on the ITO surface, facilitate the formation of dense and humidity-resistant hole-selective layer (HSL) on substrates, and improve hole transport capabilities. With the aid of the Mx-SAM strategy, the optimized wide-bandgap PSCs achieved an impressive power conversion efficiency (PCE) of 22.63% with an exceptionally high fill factor (FF) of 86.67% using the 1.68 eV perovskite. Moreover, they exhibited enhanced stability under damp-heat conditions (ISOS-D-3, 85% RH, 85 °C) with a T₉₀ of 900 h for encapsulated PSCs, representing one of the best performances for wide-bandgap PSCs. When further extending the Mx-SAM strategy to making P/S-TSCs using silicon wafers from industry, a remarkable efficiency of 28.07% is reached while upholding outstanding reproducibility. This strategy holds significant promise for the feasibility of fabricating industrially-compatible P/S-TSCs.

An air-stable n dopant named EMIC is introduced to perovskite films, which can effectively n dope perovskite films and prolong electron diffusion length to over 1.21 microns. The doped perovskite solar cells and modules processed by blade-coating realize high power conversion efficiencies of 24.3% and 20.6% at 7.4 mm² and 25.0 cm² aperture areas, respectively.

Abstract

N doping is an essential strategy to prolong electron diffusion length and improve the photovoltaic performance of p–i–n structured perovskite solar devices, but current n-dopants generally suffer from air instability, poor compatibility with perovskites, and the compensation from perovskite intrinsic defects, thus limiting their doping effectiveness. To address these issues, in this work, a new perovskite n-doping strategy is developed by incorporating an air-stable n-dopant (1-ethyl-3-methylimidazolium-2-carboxylate, EMIC) that has no detrimental effects on perovskite crystallinity and morphology. EMIC is soluble in most polar solvents and can be readily introduced into perovskite precursor solutions. Upon thermal annealing of perovskite films, the decarboxylation of EMIC releases imidazolylidene, a reactive species that highly tends to donate electrons and thus efficiently prolongs the electron diffusion length from 0.57 µm to over 1.21 µm. As a result, the blade-coated perovskite solar cells and modules realize high power conversion efficiencies of 24.3% and 20.6% at 7.4 mm² and 25.0 cm² aperture areas, respectively.

Modulating the redistribution of excess lead iodide in perovskite films by introducing N-Methyl-2-pyrrolidone in the precursor solution, excess lead iodide migrates toward the perovskite film surface during formation, significantly reducing its presence at the buried interface. The blade-coated inverted perovskite solar cells exhibits an efficiency of up to 24.5% and the developed large-area modules achieved 20.3% efficiency.

Abstract

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

A novel discontinuous interconnection based on a dashed P2 contact is developed to minimize the efficiency losses from cell to module. In this way, it is possible to achieve a record geometrical fill factor of 99.6% (active area divided by the sum of active area and interconnection area), without inducing any resistive losses, achieving a minimodule efficiency of 20.6%.

Abstract

Perovskite solar cells, known for high efficiency and compatibility with various photovoltaic (PV) applications, have garnered significant attention from academia and industry. Scaling up these cells conventionally involves fabricating modules with series-connected cells using a monolithic interconnection based on the P1-P2-P3 scheme, a common approach for thin-film PV modules. The Geometrical Fill Factor (GFF), representing the ratio between active area and aperture area, typically ranges from 90% to 95%. This study introduces an advanced laser manufacturing process to minimize interconnection area by reducing scribe width and minimizing distances between them, achieving an interconnection width of 45 µm with a GFF of 99.1%. Additionally, a discontinuous P2 design further reduces the dead area to an average of 19.5 µm, resulting in a record GFF of 99.6%. Using this interconnection in a highly efficient p-i-n stack, the study demonstrates the feasibility of the discontinuous P2 by fabricating 2.6 cm² minimodules with an aperture area efficiency of 20.7%. The research highlights how proper design can minimize intrinsic losses during the scaling process from cell to module to a negligible level. Experimental studies, coupled with cell-to-module loss simulations and electroluminescence mapping for layer deposition uniformity, provide insights into the potential of the new P2 design.

This study demonstrates the impressive outdoor stability of perovskite solar cells previously tested indoors. The cells are monitored for six months under two realistic operating conditions. The cell connected to a resistance remains stable, whereas the one with maximum power point tracking and current–voltage curve tracing starts degrading. Results suggest that concealed electronic equipment malfunctions trigger this premature degradation.

Perovskite solar cells (PSCs) have sparked great excitement in the photovoltaics community due to their remarkable efficiency, flexibility, and ability to be synthesized at low cost. However, their instability poses a major roadblock to their widespread adoption. Recognizing this challenge, this work describes the performance of stable PSCs operating under real-life conditions in the Paris area. Two state-of-the-art 2D/3D (HOOC(CH₂)₄NH₃)2PbI₄/CH₃NH₃PbI₃ encapsulated cells are considered—one with maximum power point tracking and hourly current–voltage curve measurements, and another connected to a fixed resistive load. Their performance is compared over six months, and a detailed analysis is conducted on the cells’ hysteresis and electrical response to varying weather conditions. Although the first cell starts to degrade after a few months of operation, the second one remains remarkably stable, highlighting critical issues with outdoor tracking. Given that the stability of this PSC architecture has already been established under controlled standard conditions for over one year, these exciting findings pave the way for the commercialization of perovskite-based photovoltaic devices.

The solution of SnO2 synthesized using highly oxidizing H2O2 exhibits reduced oxygen vacancies and defects compared with conventional SnO2, leading to enhanced performance. To minimize internal and external defects, ultrasonic waves were employed to activate the interfaces of SnO2, followed by the addition of FACl to form Cl−-containing SnO2. Consequently, the synthesized SnO2 demonstrated the highest efficiency of 26.05% (certified 25.54%) with an aperture area of 0.096 cm2.

Publication date: August 2024

Source: Nano Energy, Volume 127

Author(s): Sixiao Gu, Jun He, Shirong Wang, Dewang Li, Hongli Liu, Xianggao Li

Dibenzo[g,p]chrysene, a non-planar double helicene, displays enhanced rigidity compared to tetraphenylethene, enabling the development of a molecular semiconductor with elevated cohesive energy density and hole mobility. Applied in high-efficiency perovskite solar cell fabrication, it exhibits remarkable operational stability at 45 °C and storage stability at 85 °C.

Abstract

Efficient and robust n-i-p perovskite solar cells necessitate superior organic hole-transport materials with both mechanical and electronic prowess. Deciphering the structure–property relationship of these materials is crucial for practical perovskite solar cell applications. Through direct arylation, two high glass transition temperature molecular semiconductors, DBC-ETPA (202 °C) and TPE-ETPA (180 °C) are synthesized, using dibenzo[g,p]chrysene (DBC) and 1,1,2,2-tetraphenylethene (TPE) tetrabromides with triphenylene–ethylenedioxythiophene-dimethoxytriphenylamine (ETPA). In comparison to spiro-OMeTAD, both semiconductors exhibit shallower HOMO energy levels, resulting in increased hole densities (generated by air oxidation doping) and accelerated hole extraction from photoexcited perovskite. Experimental and theoretical studies highlight the more rigid DBC core, enhancing hole mobility due to reduced reorganization energy and lower energy disorder. Importantly, DBC-ETPA possesses a higher cohesive energy density, leading to lower ion diffusion coefficients and higher Young's moduli. Leveraging these attributes, DBC-ETPA is employed as the primary hole-transport layer component, yielding perovskite solar cells with an average efficiency of 24.5%, surpassing spiro-OMeTAD reference cells (24.0%). Furthermore, DBC-ETPA-based cells exhibit superior operational stability and 85 °C thermal storage stability.

In this study, to overcome the wettability issue of highly hydrophobic self-assembled monolayer (SAM), a new SAM deposition method based on a vacuum-assisted deposition (VD) process was attempted. The VD process improved the performance of PSCs by improving the wettability of the hydrophobic SAM layer. This finding can provide a cornerstone for using highly hydrophobic SAM-based hole transport layer.

Recently, various carbazole-based self-assembled monolayers (SAMs) have been investigated for use in the hole transport layer (HTL) of perovskite solar cells (PSCs). In particular, [4-(3,6-dimethyl-9H-carbazol-9-yl)butyl] phosphonic acid (Me-4PACz) is attracting attention as an HTL for high-efficiency PSC due to its potential for high open-circuit voltage (V _OC) and fill factor (FF). However, Me-4PACz has strong hydrophobicity due to its methyl group (–CH₃) and long alkyl chain (C4H₈), which makes it difficult to deposit a high-quality perovskite layer on top of conventionally coated Me-4PACz. In this study, to overcome these limitations, a new SAM deposition method based on a vacuum-assisted deposition (VD) process is attempted. As a result, a uniform perovskite layer is deposited on top of Me-4PACz through a very simple VD process, achieving 20.31% efficiency, which is not only close to the highest efficiency among Me-4PACz-based PSCs, but also improved long-term stability of the device. It is believed that the findings of this study can be a cornerstone for using SAM-based HTL with high hydrophobicity in the future.

Large-area near-infrared-transparent perovskite mini-modules with excellent uniformity and minimal spread in device performance achieve with fully scalable process by employing bilayer hole transport layer stack of sputtered NiO and blade-coated MeO-2PACz. In combination with CIGS bottom module, fully scalable 4-terminal perovskite-CIGS tandem modules with 20.5% power conversion efficiency are demonstrated.

The use of carbazole-based self-assembled monolayer (SAM) as a hole transport layer (HTL) has led to the efficiency advancement in p–i–n perovskite solar cells (PSCs). However, PSCs with SAM HTL display a large spread in device performance even on small-area substrates owing to poor SAM surface coverage and dewetting of the perovskite ink. Efforts to improve the uniformity in device performance of SAM-based PSCs have been confined to spin-coating method, which lacks high-throughput capabilities and leads to excessive material wastage. Herein, a scalable bilayer HTL stack with sputtered NiO and blade-coated SAM is utilized to achieve improved SAM coverage and accomplish uniform coating of perovskite absorber on 5 cm × 5 cm substrates. Fully scalable p–i–n PSCs with efficiency close to 19% with a minimal spread in device performance are achieved. To showcase the upscaling potential, near-infrared-transparent perovskite mini-modules with efficiency close to 15% and 13% are achieved on an aperture area of 2.56 and 12.96 cm². Together with low-bandgap (1.0–1.1 eV) Cu(In,Ga)Se₂ (CIGS) mini-modules, the first fully scalable 4-terminal perovskite-CIGS tandem mini-module with an efficiency of 20.5% and 16.9% on an aperture area of 2.03 and 10.23 cm² is demonstrated.

By employing a ligand exchange strategy with (11-mercaptoundecyl)-N,N,N-trimethylammonium bromide (MUTAB), the authors capitalized on lead-sulfur (Pb−S) interactions. MUTAB passivates the nanocrystal (NC) surface, ensuring water dispersibility and stability, unlike oleyl amine/oleic acid (OAm/OAc)-capped counterparts prone to rapid degradation. The optoelectronic properties of MUTAB-stabilized NCs are validated through efficient 3,3′,5,5′-tetramethylbenzidine (TMB) oxidation under visible light irradiation.

Abstract

Lead halide perovskite nanocrystals (LHP NCs) have garnered attention as promising light-harvesting materials for optoelectronics and photovoltaic devices, attributed to their impressive optoelectronic properties. However, their susceptibility to moisture-induced degradation has hindered their practical applications. Despite various encapsulation strategies, challenges persist in maintaining their stability and optoelectronic performance simultaneously. Here, a ligand exchange approach is proposed using (11-mercaptoundecyl)-N,N,N-trimethylammonium bromide (MUTAB) to enhance the stability and dispersibility of CsPbBr₃ (CPB) NCs in aqueous environments. MUTAB enables effective surface passivation of the CPB NCs via robust Pb–S interactions at the S-terminal while concurrently directing water molecules through the unbound cationic N-terminal or vice versa, ensuring water dispersibility and stability. Spectroscopic analysis confirms retained structural and optical integrity post-ligand exchange. Crucially, MUTAB-bound CPB NCs exhibit sustained charge transfer properties, demonstrated by aqueous colloidal oxidation reactions. This ligand exchange strategy offers a promising pathway for advancing LHP NCs toward practical optoelectronic and photocatalytic applications.

Blue perovskite quantum dot-based light-emitting diode (QLED) with an external quantum efficiency (EQE) of 23.5% at 490 nm is achieved through a combination of quantum dot (QD) passivated by trifluoroacetate and optimal device design through a mixed hole-transport layer. The work breaks through the EQE gap of 20% for blue perovskite-based QLEDs and significantly promotes their commercialization process.

Abstract

Perovskite quantum dot-based light-emitting diodes (QLEDs) have been considered a promising display technology due to their wide color gamut for authentic color expression. Currently, the external quantum efficiency (EQE) for state-of-the-art blue perovskite QLEDs is about 15%, which still lags behind its green and red counterparts (>25%) and blue film-based LEDs. Here, blue perovskite QLEDs that achieve an EQE of 23.5% at 490 nm is presented, to the best knowledge, which is the highest value reported among blue perovskite-based LED fields. This impressive efficiency is achieved through a combination of quantum dot (QD) passivation and optimal device design. First, blue mixed halide perovskite CsPbCl_{3− x} Br _x QDs passivated by trifluoroacetate exhibit excellent exciton recombination behavior with a photoluminescence quantum yield of 84% due to reducing uncoordinated Pb surface defects. Furthermore, the device is designed by introducing a mixed hole-transport layer (M-HTL) to increase hole injection and transportation capacity and improve carrier balance. It is further found that M-HTL can decrease carrier leakage and increase radiative recombination in the device, evidenced by the visual electroluminescence spectrum at 2.0 V. The work breaks through the EQE gap of 20% for blue perovskite-based QLEDs and significantly promotes their commercialization process.

The study reports the synthesis of the first crystalline 2D fullerene-based metal halide semiconductor, namely (C₆₀-2NH₃)Pb₂I₆. Utilization of the C₆₀-2NH₃I₂ adduct as an interfacial layer in mixed Pb-Sn perovskite solar cells substantially improved both carrier transport and device stability. This work sets the foundation for the development of a new family of multifunctional materials, namely Fullerene Metal Halide Semiconductors.

Abstract

Despite advances in mixed tin-lead (Sn-Pb) perovskite-based solar cells, achieving both high-efficiency and long-term device stability remains a major challenge. Current device deficiencies stem partly from inefficient carrier transport, originating from defects and improper band energy alignment among the device's interfaces. Developing multifunctional interlayer materials simultaneously addressing the above concerns poses an excellent strategy. Herein, through molecular and crystal engineering, an amine-functionalized C₆₀ mono-adduct derivative (C₆₀-2NH₃ = bis(2-aminoethyl) malonate-C₆₀) is utilized for the synthesis of the first crystalline fullerene-based 2D metal halide semiconductor, namely (C₆₀-2NH₃)Pb₂I₆. Single crystal XRD studies elucidated the structure of the new material, while DFT calculations highlighted the strong contribution of C₆₀-2NH₃ to the electronic density of states of the conduction band of (C₆₀-2NH₃)Pb₂I₆. Utilization of C₆₀-2NH₃ as an interlayer between a FA_0.6MA_0.4Pb_0.7Sn_0.3I₃ perovskite and a C₆₀ layer offered superior band energy alignment, reduced nonradiative recombination, and enhanced carrier mobility. The corresponding perovskite solar cell (PSC) device achieved a power conversion efficiency (PCE) value of 21.64%, maintaining 90% of its initial efficiency, after being stored under a N₂ atmosphere for 2400 h. This work sets the foundation for developing a new family of functional materials, namely Fullerene Metal Halide Semiconductors, targeting applications from photovoltaics to catalysis, transistors, and supercapacitors.

A facile and eco-friendly dimethyl sulfoxide-mediated solution aging (DMSA) treatment is proposed to homogenize the morphology and composition of methylammonium-free wide-bandgap perovskite films, which contributes to highly efficient and stable semitransparent perovskite solar cells and tandem solar cells.

Abstract

A facile and eco-friendly dimethyl sulfoxide-mediated solution aging (DMSA) treatment is presented to control the crystallization dynamics of methylammonium (MA)-free wide-bandgap (WBG) perovskite films, enhancing film quality, and morphology for high-performance tandem solar cells. The comprehensive structural, morphological, and characterization analyses reveal that the DMSA treatment significantly enhances composition and morphology homogeneity while suppressing halide segregation. Consequently, opaque, and semi-transparent MA-free WBG perovskite solar cells (PSCs) exhibit remarkable power conversion efficiencies (PCEs) of 18.28% and 17.61%, respectively. Notably, the unencapsulated DMSA-treated devices maintain 95% of the initial PCE after 900 h of continuous operation at 55 °C ± 5 °C. Furthermore, stacking semi-transparent DMSA-treated PSCs as top cells in a 4T tandem configuration, along with silicon heterojunction (SHJ), lead–tin (Pb–Sn) alloyed PSCs, and organic photovoltaics (OPV) as bottom cells, yields impressive PCEs of 28.09%, 26.09%, and 25.28%, respectively, for the fabricated tandem cells. This innovative approach opens new avenues for enhancing the photo-stability and photovoltaic performance of perovskite-based tandem solar cells.

Self-assembled monolayer (SAM) molecules are extensively employed in perovskite solar cells, serving both as charge transport materials and interfacial modulators. These molecules play a crucial role in adjusting surface energy levels, reducing interfacial trap defects, and enhancing perovskite crystallization quality, thereby leading to improved performance and stability of perovskite solar cells.

Abstract

Perovskite solar cells (PSCs) hold significant promise as the next-generation materials in photovoltaic markets, owing to their ability to achieve impressive power conversion efficiencies, streamlined fabrication processes, cost-effective manufacturing, and numerous other advantages. The utilization of self-assembled monolayer (SAM) molecules has proven to be a significant success in enhancing device efficiency and extending device stability. This review highlights the dual use of SAM molecules in the realm of PSCs, which can not only serve as charge transport materials but also act as interfacial modulators. These research endeavors encompass a wide range of applications for various SAM molecules in both n-i-p and p-i-n structured PSCs, providing a deep insight into the underlying mechanisms. Furthermore, this review proposes current research challenges for future investigations into SAM materials. This timely and thorough review seeks to provide direction and inspiration for current research efforts dedicated to the ongoing incorporation of SAMs in the field of perovskite photovoltaics.