Solar Cells Research Articles

A Scorpion−type Dopant‐Free Hole Transport Material for n‐i‐p Organic−Inorganic Hybrid Perovskite Solar Cells

It is significant to develop dopant‐free hole transport materials (HTMs) to improve the long‐term stability of n‐i‐p organic−inorganic hybrid perovskite solar cells (PSCs). In this work, two HTMs (DTTP‐T and DTTP‐D) based on dithienothiopyrrole (DTTP) core were synthesized to explore the effects of different substituents on the nitrogen atom on the properties of HTMs. Compared with anisole‐substituted DTTP‐D, triarylamine‐substituted scorpion‐type DTTP‐T shows better matching energy level, stronger charge transfer and defect passivation ability. Therefore, the power conversion efficiency (PCE) of dopant‐free DTTP‐T‐based n‐i‐p PSCs reaches 18.67%, which is comparable to that of doped Spiro‐OMeTAD (19.51%). More encouragingly, the efficiency of DTTP‐T‐based devices remains above 80% of its initial efficiency after 1728 h of storage in air, while the Spiro‐OMeTAD‐based devices could only maintain 600 h. This work provides a good reference for the development of dopant‐free small molecular HTMs for efficient and stable PSCs.

Quasi‐Planar Core Based Spiro‐Type Hole‐Transporting Material for Dopant‐Free Perovskite Solar Cells

AbstractHole‐transporting material (HTMs) are crucial for obtaining the stability and high efficiency of perovskite solar cells (PSCs). However, the current state‐of‐the‐art n‐i‐p PSCs relied on the use of 2,2′,7,7′‐tetrakis(N,N‐di‐p‐methoxyphenylamine)‐9,9′‐spirobifluorene (spiro‐OMeTAD) exhibit inferior intrinsic and ambient stability due to the p‐dopant and hydrophilic Li‐TFSI additive. In this study, a new spiro‐type HTM with a critical quasi‐planar core (Z‐W‐03) is developed to improve both the thermal and ambient stability of PSCs. The results suggest that the planar carbazole structure effectively passivates the trap states compared to the triphenylamine with a propeller‐like conformation in spiro‐OMeTAD. This passivation effect leads to the shallower trap states when the quasi‐planar HTMs interact with the Pb‐dimer. Consequently, the device using Z‐W‐03 achieves a higher Voc of 1.178 V compared to the spiro‐OMeTAD's 1.155 V, resulting in an enhanced efficiency of 24.02 %. In addition, the double‐column π–π stacking of Z‐W‐03 results in high hole mobility (~10−4 cm2 V−1 s−1) even without p‐dopant. Moreover, when the surface interface is modified, the undoped Z‐W‐03 device can achieve an efficiency of nearly 23 %. Compared to the PSCs using spiro‐OMeTAD, those with Z‐W‐03 exhibit enhanced stability under N2 and ambient conditions. This superior performance is attributed to the quasi‐planar core structure and the presence of multiple CH/π and π–π intermolecular stacking in Z‐W‐03. The multiple CH/π and π–π intermolecular contacts of HTMs can improve the hole hopping transport. Therefore, it is imperative to focus on further molecular structure design and optimization of spiro‐type HTMs incorporating quasi‐planar cores and carbazole moieties for the commercialization of PSCs.

Enchanting optical, electronic, and mechanical properties of the sodium based Na2MgSiZ6 (Z = I, Br, Cl) halides have been explored through DFT

Materials. with perovskite structures have been extensively studied due to their remarkable properties, which are important in various aspects of daily life. In the present approach, Na2MgSiZ6 (Z = I, Br, Cl) halides were extensively studied, and it was realized from the band structure results that all these halides display semiconducting natures with indirect band gaps. The semiconducting natures of Na2MgSiZ6 (Z = I, Br, Cl) halides were further confirmed by their TDOS results. The optimized values of the lattice constants were found to be 11.70 Å, 10.4 Å, and 10.22 Å for Na2MgSiI6, Na2MgSiBr6, and Na2MgSiCl6, respectively. Moreover, the largest volume was observed for the Na2MgSiI6 compound, while the smallest volume was recorded for the Na2MgSiCl6 compound. Na2MgSiCl6 compound exhibited brittle nature, whereas Na2MgSiBr6 and Na2MgSiI6 were found to be ductile. All three materials demonstrated attractive values of optical conductivities, making them befitting candidates for solar cells, LEDs, detectors, and various other optoelectronic devices. From the achieved negative values of formation energy for all the Na2MgSiZ6 (Z = I, Br, Cl) halides, it was comprehended that these compounds could be synthesized practically.

Constructing Bionic Perovskite Smart Photovoltaic Windows with Switchable Colors and High Cycling Stability.

Smart photovoltaic windows (SPWs) provide a high-efficiency and energy-saving strategy owing to the dual capabilities of electricity generation and sunlight modulation achieved by tunable colors and transmittances. Due to the deterioration of chromic process on photovoltaic layers, SPWs usually suffer from poor cycling stability. Moreover, thermochromic SPWs with a multilayer structure usually change transmittance without reversible color transitions. To address these issues, inspired by chameleon skin, bionic SPWs are designed and constructed by integrating hydrogel, CsPbBr3 semitransparent perovskite solar cells (ST-PSCs), and transparent polymer film. The SPWs realize reversible transitions between transparent green (25°C) and opaque yellow (45°C) states in a short duration (2min) under natural conditions. By optimizing perovskite film and ultrathin-metal electrodes, CsPbBr3 ST-PSCs achieve a good trade-off between transmittance and efficiency, delivering the highest photovoltaic efficiency (8.35%) and a record light utilization efficiency (4.43). Ultimately, the multilayer SPWs maintain stable optical properties and more than 88% initial conversion efficiency after 100 transition cycles, presenting excellent cycling stability. This study proposes a novel approach and device structure for SPWs with high cycling stability, switchable colors, and switchable transmittances. It also paves the way for smart photovoltaic deployment in buildings and many other fields.

High Performance Perovskite Solar Cells Based on Multifunctional Additives of Crown‐Ether‐Iodine Supra‐Molecules

AbstractThe efficiency and stability of perovskite solar cells (PSCs) are influenced by various factors, such as controlling the migration of iodide anion (I−) and lithium cation (Li+), oxidizing the hole‐transport material of 2,2′,7,7′‐tetras(N,N‐p‐methoxyaniline)‐9,9′‐spirodifluorene (Spiro), and passivating the perovskite film. Herein, three multifunctional crown‐ether‐iodine (crown‐ether‐I2) supra‐molecules are investigated as activities in the hole transport layers (HTLs). Results indicate that the crown‐ether‐I2 can slowly release I2 to gently oxidize Spiro, and significantly improve the efficiency of PSCs. Moreover, the crown‐ether can contribute to stabilizing Li+ in HTL and passivating the defect sites on the upper interface of the perovskite layer, which can enhance the long‐term stability of PSCs. Furthermore, crown‐ether‐I2 can absorb I− to produce crown‐ether‐I3−, which can discharge I− to promote the self‐healing of I− defects and inhibit the migration of I− in the perovskite film, thereby further enhancing PSC's long‐term stability. PSC based on Dbenzo‐24‐Crown‐8‐Ether‐Iodine (DB24C8‐I2) achieves an impressive efficiency of 24.29%, which is much higher than that of the control device (22.28%). Additionally, the stability of the un‐encapsulated PSC with DB24C8‐I2 is significantly enhanced, while maintaining 96.9% of its original efficiency after 2000 h. This work provides an effective strategy for improving the efficiency and long‐term stability of PSCs.

CaF2 Nanoparticle-Induced γ-CsPbI2.81Br0.19 Heterogeneous Crystallization for High-Efficiency Flexible All-Inorganic Perovskite Solar Cells.

All-inorganic CsPbI3 films necessitate higher annealing temperatures for high-quality crystallization. Consequently, the conventional low-temperature solution approach often results in poor crystallization in flexible CsPbI3 films, significantly degrading the optoelectronic performance and stability of flexible perovskite solar cells (f-PSCs). Herein, a heterogeneous CaF2 nanocrystal seed-induced strategy has been successfully utilized to achieve enhanced crystallization of a flexible CsPbI2.81Br0.19 film. Due to their good lattice match with the perovskite material, CaF2 nanoparticles can decrease the critical Gibbs free energy of CsPbI2.81Br0.19 perovskite nucleation, thereby accelerating γ-phase CsPbI2.81Br0.19 crystallization at low temperatures. This leads to an improved crystalline quality of the flexible perovskite film at low temperatures, which minimizes defects and enhances the stability of f-PSCs. The CsPbI2.81Br0.19 f-PSCs achieved a champion power conversion efficiency of 15.03% and demonstrated mechanical stability, retaining 98.1% of their initial efficiency even after 60 000 bending cycles with a curvature radius of 5 mm.

Tetrahydrofuran Processable Organic Solar Cells with 19.45% Efficiency Realized by Introducing High Molecular Dipole Unit Into the Terpolymer.

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

Design and Simulation for Minimizing Non-Radiative Recombination Losses in CsGeI2Br Perovskite Solar Cells.

CsGeI2Br-based perovskites, with their favorable band gap and high absorption coefficient, are promising candidates for the development of efficient lead-free perovskite solar cells (PSCs). However, bulk and interfacial carrier non-radiative recombination losses hinder the further improvement of power conversion efficiency and stability in PSCs. To overcome this challenge, the photovoltaic potential of the device is unlocked by optimizing the optical and electronic parameters through rigorous numerical simulation, which include tuning perovskite thickness, bulk defect density, and series and shunt resistance. Additionally, to make the simulation data as realistic as possible, recombination processes, such as Auger recombination, must be considered. In this simulation, when the Auger capture coefficient is increased to 10-29 cm6 s-1, the efficiency drops from 31.62% (without taking Auger recombination into account) to 29.10%. Since Auger recombination is unavoidable in experiments, carrier losses due to Auger recombination should be included in the analysis of the efficiency limit to avoid significantly overestimating the simulated device performance. Therefore, this paper provides valuable insights for designing realistic and efficient lead-free PSCs.

Comprehensive study on the optoelectronic properties of ZnSnP2 compound by DFT and simulation for the application in a photodetector

Abstract This article presents the density function theory (DFT) calculation of ZnSnP2 (ZTP) and its application as a photodetector. A DFT calculation has been performed to determine ZTP's optical and electronic characteristics. The direct bandgap of ZnSnP2 is found to be 1.0 eV which agrees well with the previously reported bandgap (0.95 eV). The total density of states (TDOS) of ZTP is determined to be 1.40 states/eV which is attributed to the 3p orbital of P, with minor impacts from the 3d orbital of Zn and the 5p orbital of Sn to TDOS. The real and imaginary dielectric functions and refractive indices ZTP have been determined to be 16.44 and 17.60, 4.07 and 2.92, respectively. The absorption coefficient and reflectivity of ZTP obtained from this investigation are 2.6×105 cm-1 and 57.5%, respectively. After calculating the electrionic and optical properties, ZTP-based n-CdS/p-ZnSnP2/p+-AlSb photodetector (PD) with CdS and AlSb as the window and back surface field (BSF) layers, respectively, has been computationally analyzed and optimized using solar cell capacitance simulator (SCAPS-1D). In a single heterojunction, the photocurrent, voltage, responsivity, and detectivity values have been obtained at 44.52 mA/cm2, 0.66 V, 0.73 A/W, and 6.81×1013 Jones, respectively. Insertion of a thin AlSb BSF layer improves the photocurrent, voltage, responsivity, and detectivity to 48.75 mA/cm2, 0.78 V, 0.86 A/W, and 8.22×1014 Jones, respectively. The outcomes are highly promising for the fabrication of a high performance ZTP-based PD in the future.

Retraction Note: Comparative analysis optical communication based renewable solar cell and quantum network for the reduction of carbon emission

Retraction Note: Comparative analysis optical communication based renewable solar cell and quantum network for the reduction of carbon emission

New absorbent layer through employing semi-transparent Cs0.05FA0.95PbI2.55Br0.45 in perovskite solar cells for solar windows: Balancing efficiency and transparency

Perovskite materials are gaining attention due to their superior photovoltaic performance and potential for transparent solar cell applications, such as solar windows and building-integrated systems. This study focuses on designing thinner Cs0.05FA0.95PbI2.55Br0.45 perovskite layers to balance transparency and power conversion efficiency (PCE). The solar cell performance improves with increased absorber layer thickness, resulting in a current density (JSC) rise from 9.98 to 21.60 mA/cm2. The optimized device achieves an open-circuit voltage (VOC) of 1.24 V, a fill factor (FF) of 80.70 %, and PCE of 20 %. For absorber thicknesses of 100–500 nm, the PCE ranges from 10.01 % to 19.45 %, while the average visible transmittance (AVT) decreases from 51.05 % to 2.63 %. These results provide insights into designing semi-transparent perovskite solar cells with a balance between efficiency and transparency.

Effect of Guanidinium Salt for Stress-Relaxation and Interfacial Engineering in Antisolvent Free Perovskite Solar Cells Fabricated Under Air Ambient.

In perovskite solar cells, the presence of stress and defects at interfaces promotes performance degradation and poor stability of the devices. The formation of these defects is more prominent in two-step antisolvent-free perovskite film fabrication. This study addresses these challenges by introducing guanidine sulfate (Gua-S) at the tin oxide/formamidinium lead iodide perovskite interface, fabricated without antisolvent under ambient air. Interfacial Gua-S enhanced morphology by forming bonds between uncoordinated Pb2+ ions and I- vacancies at the interface and showed improvement in the crystallinity and quality of the perovskite film. Microstructural stress analysis indicated a substantial reduction in stress, decreasing from 50.6 to 20.72 MPa with the application of Gua-S. Moreover, the Gua-S treated solar cells showed significant improvements and achieved an open circuit voltage of 1.08 V and 22.34% efficiency. Further, electrochemical impedance spectroscopic analysis showed improved built-in potential, carrier lifetime, and charge recombination lifetime for treated devices. The devices retained over 87% of the initial power conversion efficiency after 2000 hours of operation. This comprehensive study addresses the fundamental issues of interfacial stress and defects in perovskite solar cells and demonstrates the efficacy of Gua-S salt in enhancing both the structural and functional aspects of the antisolvent-free device fabrication process.

Passivation of Deep‐Level Defects through Chemical Environment Regulation for Efficient CZTSSe Solar Cells Based on Active Selenium Adsorption–Desorption Process

AbstractInsufficient selenization and uneven distribution of elements caused by the poor diffusion and reaction activity of selenium clusters is one of the main issues limiting the efficiency of Cu2ZnSn(S,Se)4 (CZTSSe) solar cells. Here, this work designs a simple and feasible strategy to improve the activity of selenium (Se) by implementing high‐temperature treatment on graphite boxes loaded with Se pellets. The rapid adsorption/desorption characteristics of graphite on active gaseous small‐molecule selenium have successfully introduced hyperactive Se4, Se3, and Se2 into the selenization process. The results indicate that the adsorbed non‐toxic gaseous active Se3 and Se4 can quickly and uniformly diffuse into the precursor film at low temperatures, thereby inducing nucleation and grain growth at both surface and back interface simultaneously, which inhibits the upward migration and aggregation of cations, especially Cu, and promotes the homogenization of elements. The overall relatively Cu‐poor chemical environment suppresses the formation of CuZn defects and [2CuZn+SnZn] defect clusters, and also promotes the generation of favorable VCu. The band tail states and non‐radiative recombination are then optimized. Finally, the CZTSSe solar cells achieve a power conversion efficiency (PCE) of 14.5%, with VOC/VOCSQ of 67% being one of the highest in the literature.

Targeted synergistic chemical bonding strategy for Efficient and stable CsPbI3-based perovskite solar cells

Regulating the crystallization process of perovskite film and suppressing iodine-related defects hold significant importance in improving the efficiency and stability of CsPbI3-based perovskite solar cells (PSCs), thereby endowing their more potential for commercial applications. Herein, we introduced 2-Aminoethyl methylsulfone hydrochloride (AMS) into the perovskite precursor solution to establish targeted synergistic chemical bonding involving Lewis acid-base interactions and hydrogen bonds with CsPbI3 perovskite. We emphasize the importance of the DMAPbI3 intermediate phase for the crystal quality of CsPbI3 perovskite, and reveal that diminishing the size of Pb-I framework colloids in precursor solution can facilitate the formation of DMAPbI3 and optimize the crystallization process of CsPbI3 perovskite. Simultaneously, we demonstrate the generation of high valence iodine defects due to the photoinduction, and prove that constructing N-H···I hydrogen bond can effectively passivate the iodine-related defects. Consequently, the CsPbI3-based PSCs display an impressive power conversion efficiency of 19.59% along with markedly improved stability. Our finding presents a feasible strategy for managing perovskite crystallization and mitigating the defects-induced perovskite degradation, thus promoting the commercialization of CsPbI3-based PSCs.

“Like dissolves like” enables the synergy of fluorinated additive and fluorous solvent soaking for high-performance organic solar cells

The pre-treatment and post-treatment of organic solar cells (OSCs) are two important device engineering processes that are closely associated with photovoltaic performance. Yet these two stages are independently developed to optimize the morphology and then improve the device performance, while their synergy is believed to be more productive. In this study, the fluorinated additive and fluorous solvent soaking (FSS) are simultaneously employed in OSCs, and the “like dissolves like” concept drives their synergetic role on the morphology optimization. The fluorinated additive 1,8-diiodoperfluorooctane (FDIO) could selectively enhance the packing order and crystallinity of the acceptor through forming the fluorine-induced interactions. Moreover, fluorous solvent could penetrate into the blend film and then remove the residue FDIO while further optimizing the morphology by enhancing molecular packing. By employing the synergy of FDIO additive and FSS treatment (40 °C for 30 s), a champion power conversion efficiency (PCE) of 18.64 % with the simultaneous improvements of photovoltaic parameters is achieved. This study provides a synergetic strategy by employing fluorinated additive and fluorous solvent to tune film morphology in the film-formation and post-treatment processes, respectively, consequently advancing the photovoltaic performance of OSCs.

Cost-Effective Acetonitrile-Based Precursor Solution Mitigates Heterogeneous Nucleation for Efficient and Stable Perovskite Solar Cells.

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

Emerging class of SrZrS3 chalcogenide perovskite solar cells: Conductive MOFs as HTLs - A game changer?

The emerging SrZrS3 chalcogenide perovskite has been suggested as a potential alternative to lead halide perovskites, offering unique optoelectronic properties while addressing concerns such as lead toxicity and instability. Our research explored its potential, demonstrating the use of conductive metal-organic frameworks (c-MOFs) Cu-MOF ({[Cu2(6-mercapto nicotinate)]·NH4}n), NTU-9, Fe2(DSBDC), Sr-MOF ({[Sr(ntca)(H2O)2]·H2O}n), Mn2(DSBDC), and Cu3(HHTP)2 as promising substitutes for traditional HTLs via SCAPS-1D. By systematically optimizing the absorber and HTL properties, maximum PCEs of 30.60 %, 29.78 %, 28.29 %, 28.44 %, 28.80 %, and 28.62 % were accomplished for solar cell devices based on the aforementioned MOFs, respectively. Comparative analysis of initial and optimized solar cells using energy band diagrams, Nyquist plots, and quantum efficiency revealed that optimized devices consistently raised quasi-Fermi levels, significantly enhanced conductivity, and boosted solar cell performance. Additionally, the high recombination resistance of 1.4 × 107 Ω cm2, improved spectral response of 35 % in the NIR region, and heightened built-in potential (∼0.99 V) resulted in the highest efficiency of 30.60 % for Cu-MOF solar cells. This research highlights the promising potential of novel SrZrS3 absorbers and the utilization of c-MOFs as HTLs in solar cells, positioning them as a game changer in the PV field.

Efficient Large Area Semi‐Transparent Dye‐Sensitized Solar Cells (DSSCs) Printed with DMD400 Technology

AbstractThis work presents the development of fully printed, large‐area, semi‐transparent Dye‐Sensitized Solar Cells (DSSCs) using TiO2 nanoparticles treated with TiCl4, a “D35” push‐pull dye sensitizer, and I3−/I− redox mediator. Cells with areas of 4 and 200 cm2 were printed using hexagonal, stripe, and standard designs, employing digital materials deposition (DMD) technology. The porous films printed via DMD, confirmed by scanning electron microscopy (SEM), improved solar cells performance by enhancing the Open Circuit Voltage (Voc) and fill factor (FF). The hexagonal design, in particular, facilitated better electrolyte impregnation in the TiO2 mesoporous structure, boosting current density. This design yielded a power conversion efficiency (PCE) of 7.05% for 4 cm2 DSSCs, surpassing the stripe (5.50%) and standard (5.48%) designs. Its higher performance can be attributed to lower interfacial charge recombination rates and improvedcharge transfer and collection efficiency. Photophysical measurements indicated faster charge transfer rates in hexagonal cells (≈ 1.3 × 109s−1) compared to the stripe (9.8 × 108 s−1) and standard (9.5 × 108 s−1) designs. Hence, our work highlights the potential of hexagonal design to improve both efficiency and transparency while reducing material consumption, offering a promising approach for manufacturing semi‐transparent solar cells.

Rational Design of Facile and Low‐Cost Construction of Carbon‐Based Dye‐Sensitized Solar Cells using Garcinia Mangostana L. as a Photosensitizer

Research on solar cell devices is not only always related to how to obtain high power conversion efficiency (PCE), but also other factors need to be fully considered, such as the cost and their ecofriendliness. In this present research, a low‐cost and ecofriendly dye‐sensitized solar cell (DSSC) is being developed using a graphite‐based nanocomposite and an unusual plant extract (Garcinia mangostana L.) as the dye photosensitizer. A rational design on how to use graphite as a photoanode and counter electrode (CE) in DSSC is carried out by combining the graphite with ZnO and multiwalled carbon nanotube (MWCNT), respectively. It is observed that graphite acts as a matrix for ZnO and MWCNT to make these nanocomposites have very appropriate optoelectronics and catalytic properties compared to the control sample. Therefore, they could serve as an excellent photoanode and CE, respectively. It is also expected that the anthocyanin absorption in Garcinia mangostana L. dye which is found in the visible light range can efficiently absorb photons, thus supporting the enhancement of photovoltaic performance of the DSSC. The generated voltage (V) and current (I) from light irradiation using commercial lamps are higher compared to halogen lamps, indicating that the obtained DSSC has potential as indoor powered devices. It is believed that our study can shed light on the development of DSSC using low‐cost material graphite as the main component for the realization of low‐cost DSSC devices.

Uniform Phase Permutation of Efficient Ruddlesden-Popper Perovskite Solar Cells via Binary Spacers and Single Crystal Coordination.

2D Ruddlesden-Popper perovskites (RPPs) have attracted extensive attention in recent years due to their excellent environmental stability. However, the power conversion efficiency (PCE) of RPP solar cells is much lower than that of 3D perovskite solar cells (PSCs), mainly attributed to their poor carrier transport performance and excessive heterogeneous phases. Herein, the binary spacers (n-butylammonium, BA and benzamidine, PFA) are introduced to regulate the crystallization kinetics and n-value phase distribution to form uniform phase permutation of RPP films. The study then incorporates n = 5 BA2MA4Pb5I16 memory single crystal to achieve ultrafast stepped-type carrier transport from the low n-value phases to the high n-value phases in the high-quality (BA0.75PFA0.25)2MA4Pb5I16 films. These binary spacers and single-crystal-assisted crystallization strategies produce high-quality films, leading to fast carrier extraction and significant nonradiative recombination suppression. The resulting PSC presents a champion PCE of 21.15% with an impressive open circuit voltage (VOC) of 1.26V, which is the record high efficiency and VOC for low n-value RPP solar cells (n ≤ 5).