Wide-bandgap Perovskite Research Articles

Crystallization Control of Blade‐Coated Wide Bandgap FACs‐Based Perovskite

AbstractTransforming perovskite solar cells into commercial production requires advanced scalable deposition technology. However, the deposition of high‐quality perovskite thin films using the blade coating method presents challenges, especially in controlling the nucleation and crystallization of perovskite. In this work, an effective approach is proposed for controlling nucleation and crystallization by simultaneously incorporating two kinds of ionic liquid, namely 1H‐imidazole acetate (IMAc), and 1‐buty‐3‐methylimidazolium tetrafluoroborate (BMIMBF4), into the precursor solution. This innovative strategy initiates π–π interactions between IM and BMIM cations, thereby enhancing the interaction between cations and the Pb‐I framework. The competitive mechanism of interaction with Pb‐I framework effectively suppresses the formation of unfavorable mesophase, thereby enabling a single crystallization pathway from NMP + PbI2 to α‐perovskite. Consequently, this method effectively reduces defects and enhances the crystal quality of α‐perovskite film. Based on this strategy, the power conversion efficiency of the p‐i‐n wide bandgap perovskite device prepared by the blade coating method, is increased to 21.31%, representing one of the highest efficiencies achieved with this technology for 1.68 eV bandgap FACs‐based perovskites. Thus, this approach emerges as a feasible breakthrough strategy that may unleash the full potential of perovskite solar cells.

Enhanced Efficiency and Intrinsic Stability of Wide-Bandgap Perovskite Solar Cells through Dimethylamine-Based Cation Engineering.

High efficiency and stable wide-bandgap perovskite solar cells (PSCs) are important for perovskite-based tandem solar cells. However, the efficiency and stability of wide-bandgap PSCs suffers from severe phase segregation and surface defects. In this study, we propose a cation engineering strategy for wide-bandgap perovskite deposited by a two-stepsequential methodthrough the incorporation ofdimethylamine hydroiodide (DMAI)into the lead halide complex in the first step. The DMAI additive modifies the crystal structure and grain growth of perovskite film, resulting in enhancing crystal quality, suppressing photo-induced halide segregation, reducing defect density, and improving charge carrier mobility. As a result, we achieved a champion photoelectric conversion efficiency (PCE) of 21.9% for 1.68 eV wide-bandgap PSCs. Additionally, the stability of PSCs based on DMA doped perovskite was strongly enhanced, after being exposed to ambient air for 1500 hours, the unencapsulated device maintained an impressive 80.6% of their initial efficiency, demonstrating great potential for stable and efficient wide-bandgap PSCs.

Boosting Carrier Transport in Quasi-2D/3D Perovskite Heterojunction for High-Performance Perovskite/Organic Tandems.

Wide-bandgap (WBG) perovskites are continuously in the limelight owing to their applicability in tandem solar cells. The main bottlenecks of WBG perovskites are interfacial non-radiative recombination and carrier transport loss caused by interfacial defects and large energy-level offsets, which induce additional energy losses when WBG perovskites are stacked with organic solar cells in series because of unbalanced carrier recombination in interconnecting layer (ICL). To solve these issues, 1,3-propanediammonium iodide (PDADI) is incorporated to form Dion-Jacobson -phase quasi-2D perovskites with mixed high-n-values in WBG perovskites. PDADI simultaneously repairs the shallow/deep defects and establishes a Type-II energy-level alignment between quasi-2D/3D and 3D perovskites for rapid carrier extraction. More importantly, the short-chain diammonium cation in quasi-2D perovskite with high n-values results in a short Pb-I inorganic layer spacing, which enhances the interlayer electronic coupling and weakens the quantum-well confinement effect that restricts carrier transport. The suppressed transport loss increases the electron concentration in the ICL for balanced carrier recombination. The 0.0628 and 1.004 cm2 perovskite/organic tandems achieve remarkable efficiencies of 25.92% and 24.63%, respectively. The quasi-2D capping layer can inhibit ion migration, allowing perovskite/organic tandems to show excellent operational stability (T85 >1000h).

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

Fullerene derivatives [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) has been routinely used as the electron transport layer (ETL) in perovskite solar cells due to its suitable energy levels and good solution processability. However, its electron mobility and conductivity still need to be further enhanced for constructing high performance perovskite solar cells (PSCs). Herein, by doping the PC61BM with a p-type polymer PM6 and n-type molecule ITIC, efficient wide-bandgap perovskite solar cells with improved efficiency and operational/storage stability are obtained. Further spectroscopy and electric measurements indicate PM6 and ITIC can both passivate defects at the perovskite/ETL interface, meanwhile ITIC can elevate the Fermi level of PC61BM to enhance conductivity and PM6 can improve the photo-induced electron mobility of the ETL, facilitating charge extraction and reducing charge recombination. As the results, Cs0.17FA0.83Pb(I0.83Br0.17)3 wide-bandgap PSCs with PM6:PC61BM:ITIC as the ETL demonstrates a superior efficiency of 22.95%, compared to 20.89% of the PC61BM assisted device.

Homogeneous crystallization of MA-free, wide-bandgap perovskite films via self-assembled monolayer capping for laminated silicon/perovskite tandem solar cells

Methylammonium (MA)-free wide-bandgap perovskite films with improved thermal/light stabilities have gained considerable attention for its application in silicon/perovskite tandem solar cells. However, compared to their MA counterparts, MA-free films often suffer from fast crystallization, resulting in uneven surface morphology, poor crystalline features, and excess PbI2 impurities. To modulate the crystallization dynamics of MA-free wide-bandgap Cs0.22FA0.78Pb(Br0.15I0.85)3 films, this study proposes a self-assembled monolayer (SAM)-capped crystallization strategy, wherein C42H52N6O4RuS2 (Z907) is added to the isopropanol antisolvent in the one-step solution process. The optimized Cs0.22FA0.78Pb(Br0.15I0.85)3 film has a wide bandgap of 1.68 eV with superior morphological/crystalline properties, enhanced thermal/moisture stability, and improved interfacial energy‐level alignment. These favorable characteristics are attributed to the efficient coupling between the positive ion vacancies in the precursor, the −SCN and –COOH functional groups in Z907, and the superhydrophobic nonyl chains in the Z907 SAM. The semitransparent perovskite solar cells (PSCs) built with the optimized Cs0.22FA0.78Pb(Br0.15I0.85)3 films demonstrate substantially high power conversion efficiencies (PCEs) of 21.63 %@0.09 cm2 and 19.12 %@1 cm2. Furthermore, based on the high-efficiency PSCs, the corresponding two-terminal laminated silicon/perovskite tandem solar cells achieved record-high PCEs of 32.07 %@0.09 cm2 and 28.32 %@1 cm2 with negligible hysteresis and improved humidity/thermal stability.

Aluminum-Doped Indium Oxide Electron Transport Layer Grown by Atomic Layer Deposition: Highly Efficient and Damage-Resistant Interconnection Solution for All-Perovskite Tandem Solar Cells with 25.46% Efficiency.

In fabricating high-efficiency all-perovskite tandem solar cells (APTSCs) with a p-i-n configuration, the electron transport layer (ETL) plays a critical role in facilitating the transport of photogenerated electrons from the front cell to the recombination layer and protecting the front cell from damage during rear cell fabrication. This study introduces aluminum-doped In2O3 (AIO) films grown by atomic layer deposition (ALD) as a promising ETL for high-efficiency APTSCs. ALD-grown AIO films with an optimized Al concentration exhibit superior charge transport characteristics, excellent transparency, and damage-resistant barrier properties against solution infiltration compared with conventional SnO2 ETLs and undoped ALD In2O3. Using an ALD SnO2/3 at.% AIO bilayer as the electron transport layer, an efficiency of 18.33% is achieved from single-junction wide bandgap perovskite solar cells. Furthermore, the use of ALD SnO2/3 at.% AIO ETL enables the reliable fabrication of APTSCs with negligible solution damage to the front cell and minimized power loss. Consequently, APTSC employing the ALD AIO-based ETL exhibit an excellent photoconversion efficiency of 25.46%, outperforming APTSCs with the ALD SnO2 ETL.

Regulation of Wide Bandgap Perovskite by Rubidium Thiocyanate for Efficient Silicon/Perovskite Tandem Solar Cells.

Developing high-quality wide bandgap (WBG) perovskites with ≈1.7eV bandgap (Eg) is critical to couple with silicon and create efficient silicon/perovskite tandem devices. The sufferings of large open-circuit voltage (VOC) loss and unstable power output under operation continuously highlight the criticality to fully develop high-quality WBG perovskite films. In this study, rubidium and thiocyanate as additive regulators in WBG perovskites are incorporated, significantly reducing non-radiative recombination, ion-migration, and phase segregation. The optimized 1.66 eV Eg perovskite solar cells achieved state-of-art 1.3V VOC (0.36V deficit), and delivered a stabilized power conversion efficiency of 24.3%, along with good device stability (20% degradation (T80) after over 994h of operation under 1 sun at ≈65°C). When integrated with a flat front side silicon cell, silicon/perovskite two-terminal tandem device (30% efficient) is obtained with a 1.97V VOC, and T90 operational lifetime of more than 600h at room temperature.

Vertically oriented low-dimensional perovskites for high-efficiency wide band gap perovskite solar cells.

Controlling crystal growth alignment in low-dimensional perovskites (LDPs) for solar cells has been a persistent challenge, especially for low-n LDPs (n < 3, n is the number of octahedral sheets) with wide band gaps (>1.7 eV) impeding charge flow. Here we overcome such transport limits by inducing vertical crystal growth through the addition of chlorine to the precursor solution. In contrast to 3D halide perovskites (APbX3), we find that Cl substitutes I in the equatorial position of the unit cell, inducing a vertical strain in the perovskite octahedra, and is critical for initiating vertical growth. Atomistic modelling demonstrates the thermodynamic stability and miscibility of Cl/I structures indicating the preferential arrangement for Cl-incorporation at I-sites. Vertical alignment persists at the solar cell level, giving rise to a record 9.4% power conversion efficiency with a 1.4 V open circuit voltage, the highest reported for a 2 eV wide band gap device. This study demonstrates an atomic-level understanding of crystal tunability in low-n LDPs and unlocks new device possibilities for smart solar facades and indoor energy generation.

Highly Durable Inverted Inorganic Perovskite/Organic Tandem Solar Cells Enabled by Multifunctional Additives.

Inverted perovskite/organic tandem solar cells (P/O TSCs) suffer from poor long-term device stability due to halide segregation in organic-inorganic hybrid wide-band gap (WBG) perovskites, which hinders their practical deployment. Therefore, developing all-inorganic WBG perovskites for incorporation into P/O TSCs is a promising strategy because of their superior stability under continuous illumination. However, these inorganic WBG perovskites also face some critical issues, including rapid crystallization, phase instability, and large energy loss, etc. To tackle these issues, two multifunctional additives based on 9,10-anthraquinone-2-sulfonic acid (AQS) are developed to regulate the perovskite crystallization by mediating the intermediate phases and suppress the halide segregation through the redox-shuttle effect. By coupling with organic cations having the desirable functional groups and dipole moments, these additives can effectively passivate the defects and adjust the alignment of interface energy levels. Consequently, a record Voc approaching 1.3 V with high power conversion efficiency (PCE) of 18.59 % could be achieved in a 1.78 eV band gap single-junction inverted all-inorganic PSC. More importantly, the P/O TSC derived from this cell demonstrates a T90 lifetime of 1000 h under continuous operation, presenting the most stable P/O TSCs reported so far.

Highly Durable Inverted Inorganic Perovskite/Organic Tandem Solar Cells Enabled by Multifunctional Additives

AbstractInverted perovskite/organic tandem solar cells (P/O TSCs) suffer from poor long‐term device stability due to halide segregation in organic–inorganic hybrid wide‐band gap (WBG) perovskites, which hinders their practical deployment. Therefore, developing all‐inorganic WBG perovskites for incorporation into P/O TSCs is a promising strategy because of their superior stability under continuous illumination. However, these inorganic WBG perovskites also face some critical issues, including rapid crystallization, phase instability, and large energy loss, etc. To tackle these issues, two multifunctional additives based on 9,10‐anthraquinone‐2‐sulfonic acid (AQS) are developed to regulate the perovskite crystallization by mediating the intermediate phases and suppress the halide segregation through the redox‐shuttle effect. By coupling with organic cations having the desirable functional groups and dipole moments, these additives can effectively passivate the defects and adjust the alignment of interface energy levels. Consequently, a record Voc approaching 1.3 V with high power conversion efficiency (PCE) of 18.59 % could be achieved in a 1.78 eV band gap single‐junction inverted all‐inorganic PSC. More importantly, the P/O TSC derived from this cell demonstrates a T90 lifetime of 1000 h under continuous operation, presenting the most stable P/O TSCs reported so far.

Efficient wide-bandgap perovskite photovoltaics with homogeneous halogen-phase distribution

Wide-bandgap (WBG) perovskite solar cells (PSCs) are employed as top cells of tandem cells to break through the theoretical limits of single-junction photovoltaic devices. However, WBG PSCs exhibit severe open-circuit voltage (Voc) loss with increasing bromine content. Herein, inhomogeneous halogen-phase distribution is pointed out to be the reason, which hinders efficient extraction of carriers. We thus propose to form homogeneous halogen-phase distribution to address the issue. With the help of density functional theory, we construct a double-layer structure (D-2P) based on 2-(9H-Carbazol-9-yl)ethyl]phosphonic acid molecules to provide nucleation sites for perovskite crystallization. Homogeneous perovskite phase is achieved through bottom-up templated crystallization of halogen component. The efficient carrier extraction reduces the Shockley-Read-Hall recombination, resulting in a high Voc of 1.32 V. As a result, D-2P-treated device (1.75 eV) achieves a record power conversion efficiency of 20.80% (certified 20.70%), which is the highest value reported for WBG (more than 1.74 eV) PSCs.

Tailoring Perovskite/C60 Interface by Reactive Passivators for Stable Tandem Solar Cells

AbstractIntegrating perovskite solar cells with crystalline silicon bottom cells in a monolithic two‐terminal tandem configuration enables power conversion efficiency (PCE) surpassing the theoretical limits of single‐junction cells. However, wide bandgap (WBG) perovskite films face challenges related to phase stability and open circuit voltage (VOC) deficit, particularly due to severe non‐radiative recombination at the perovskite/C60 interface. Here, the interfacial defects are passivated by incorporating a reactive passivator that reacts with lead halides to form low‐dimensional phases. The target product obtained by optimizing the reaction temperature not only suppresses recombination across the interface, but also facilitates the transfer of charge carriers. More importantly, this product can suppress phase segregation of WBG perovskite films under exposure to light illumination and moisture. This strategy enables a high VOC of 1.25 V for WBG perovskite device based on polymer hole transport layer and a certified stabilized PCE of 30.52% for a monolithic perovskite/silicon tandem solar cell. The unencapsulated tandem device retains 94% of its initial PCE over 200 h under continuous 1‐sun full spectrum illumination in air, demonstrating the improved phase stability.

Homogenized contact in all-perovskite tandems using tailored 2D perovskite.

The fabrication of scalable all-perovskite tandem solar cells is considered an attractive route to commercialize perovskite photovoltaic modules1. However, The certified efficiency of 1-cm2 scale all-perovskite tandem solar cells lags behind their small-area (~0.1 cm2) counterparts2,3. This performance deficit originates from inhomogeneity in wide-bandgap (WBG) perovskite solar cells (PSCs) at a large scale. The inhomogeneity is known to be introduced at the bottom interface and within the perovskite bulk itself4,5. Here we uncover another crucial source for the inhomogeneity - the top interface formed during the deposition of the electron transport layer (ETL, C60). Meanwhile, the poor ETL interface is also a significant limitation of device performance. We address this issue by introducing a mixture of 4-fluorophenethylamine (F-PEA) and 4-trifluoromethyl-phenylammonium (CF3-PA) to create a tailored two-dimensional perovskite layer (TTDL), in which F-PEA forms a two-dimensional perovskite at the surface reducing contact losses and inhomogeneity, CF3-PA enhances charge extraction and transport. As a result, we demonstrate a high open-circuit voltage of 1.35 V and an efficiency of 20.5% in 1.77-eV WBG PSCs at a square centimeter scale. By stacking with a narrow-bandgap perovskite sub-cell, we report 1.05 cm2 all-perovskite tandem cells delivering 28.5% (certified 28.2%) efficiency, the highest among all reported so far. Our work showcases the importance of treating the top perovskite/ETL contact for upscaling perovskite solar cells.

Isomeric diammonium passivation for perovskite-organic tandem solar cells.

In recent years, perovskite has been widely adopted in series-connected monolithic tandem solar cells (TSCs) to overcome the Shockley-Queisser limit of single-junction solar cells. Perovskite/organic TSCs, comprising a wide-bandgap (WBG) perovskite solar cell (pero-SC) as the front cell and a narrow-bandgap organic solar cell (OSC) as the rear cell, have recently drawn attention owing to the good stability and potential high power conversion efficiency (PCE)1,2,3,4. However, WBG pero-SCs usually exhibit higher voltage losses than regular pero-SCs, which limits the performance of TSCs5,6. One of the major obstacles comes from interfacial recombination at the perovskite/C60 interface, and it is important to develop effective surface passivation strategies to pursue higher PCE of perovskite/organic TSCs7. Here we exploit a new surface passivator cyclohexane 1,4-diammonium diiodide (CyDAI2), which naturally contains two isomeric structures with ammonium groups on the same or opposite sides of the hexane ring (denoted as cis-CyDAI2 and trans-CyDAI2, respectively), and the two isomers demonstrate completely different surface interaction behaviors. The cis-CyDAI2 passivation treatment reduces the Quasi-Fermi level splitting (QFLS)-open circuit voltage (Voc) mismatch of the WBG pero-SCs with a bandgap of 1.88 eV and enhanced its Voc to 1.36 V. Combining the cis-CyDAI2 treated perovskite and the organic active layer with a narrow-bandgap of 1.24 eV, the constructed monolithic perovskite/organic TSC demonstrates a PCE of 26.4% (certified as 25.7%).

High-performance wide-bandgap perovskite solar cells using poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) as the electron-transport layer

We used work-function-tuned poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as the electron-transport layer for wide-bandgap (1.74 eV) perovskite solar cells (PSCs). With the coating of polyethylenimine, the work function of PEDOT:PSS was modified from −5.03 to −4.05 eV, which enabled efficient electron transportation from perovskite absorber to cathode. With this technique, the standard-structured n-i-p PSCs showed an average power-conversion-efficiency (PCE) of 18.6 %, which is higher than that (17.5 %) of inverted PSCs with PEDOT:PSS as the hole-transport layer. Moreover, the long-term stability of the PSCs was enhanced with the PCE degradation significantly suppressed from 29.7 % to 15.6 % after a 10 days’ measurement in ambient.

Highly Efficient Wide Bandgap Perovskite Solar Cells With Tunneling Junction by Self-Assembled 2D Dielectric Layer.

Reducing non-radiative recombination and addressing band alignment mismatches at interfaces remain major challenges in achieving high-performance wide-bandgap perovskite solar cells. This study proposes the self-organization of a thin two-dimensional (2D) perovskite BA2PbBr4 layer beneath a wide-bandgap three-dimensional (3D) perovskite Cs0.17FA0.83Pb(I0.6Br0.4)3, forming a 2D/3D bilayer structure on a tin oxide (SnO2) layer. This process is driven by interactions between the oxygen vacancies on the SnO2 surface and hydrogen atoms of the n-butylammonium cation, aiding the self-assembly of the BA2PbBr4 2D layer. The 2D perovskite acts as a tunneling layer between SnO2 and the 3D perovskite, neutralizing the energy level mismatch and reducing non-radiative recombination. This results in high power conversion efficiencies of 21.54% and 19.16% for wide-bandgap perovskite solar cells with bandgaps of 1.7 and 1.8 eV, with open-circuit voltages over 1.3 V under 1-Sun illumination. Furthermore, an impressive efficiency of over 43% is achieved under indoor conditions, specifically under 200 lux white light-emitting diode light, yielding an output voltage exceeding 1 V. The device also demonstrates enhanced stability, lasting up to 1,200 hours.

Defect passivation engineering for achieving 4.29% light utilization efficiency MA-free wide-bandgap semi-transparent perovskite solar cells

Wide-bandgap perovskite materials are a great candidate for semitransparent perovskite solar cells (ST-PSCs) due to their tunable bandgap, outstanding transparency, and excellent photovoltaic performance. Though Br-rich perovskite can widen the bandgap, Br influences the crystallization dynamic speed leaving small perovskite grain sizes and high defects. Surface passivation engineering has been one of the best choices to suppress defects caused by the rapid crystallization of Br-rich perovskites. Herein, we applied MA-free perovskite as a light absorber because of the erratic thermal aging of MA-containing perovskites and selected phenethylammonium iodide (PEAI) and 4-trifluoro phenylethylammonium iodide (CF3PEAI) as passivation materials for improving the performance of opaque PSCs and ST-PSCs. Consequently, CF3PEA possesses a larger dipole moment. It has been demonstrated to exhibit a stronger binding energy with the substrate than PEA by density functional theory (DFT) calculations. This enhanced molecular interaction underpins the performance improvements in our solar cells, which manifests as an inverted planar structure opaque PSCs with 1.78 eV bandgap achieve a power conversion efficiency (PCE) of 17.09 % with excellent stability. A PCE of 17.17 % with 25 % average visible-light transmittance (AVT) and 4.29 % light utilization efficiency (LUE) of ST-PSCs is achieved by further optimizing the fabrication process of the buffer layer for protecting the perovskites from the damage of ITO sputter. Meanwhile, a four-terminal tandem solar cell with ST-PSC and silicon-based passivated emitter rear cell (PERC) obtains a PCE of 26.28 %. This work provides a feasible way to fabricate high-performance ST-PSCs with limited materials and preparation conditions.

Optical Simulations of Nanotextured All‐Perovskite Tandem Solar Cells

AbstractThis numerical study investigates, how textures at various locations of all‐perovskite tandem solar cells affect their optical performance. For this, hexagonal sinusoidal textures with 750 nm period and aspect ratios (height‐to‐period) of 27% (moderate) and 54% (pronounced) are considered. The optical simulations are performed with the finite element method and an algorithm to correct for the thick glass superstrate. The complex refractive index data of the wide‐bandgap (WBG) and narrow‐bandgap (NBG) perovskites with spectroscopic ellipsometry is determined. Texturing between the glass superstrate and the WBG perovskite top cell has an antireflective effect across the whole wavelength region. In contrast, texturing between the WBG perovskite top cell and the NBG perovskite bottom cell has no additional effect for a moderate texture but leads to light trapping in the NBG perovskite for a pronounced texture. Moderate texturing between the NBG perovskite absorber and the metal back contact leads to light trapping in the NBG perovskite but also excites surface plasmons in the copper back contact. Dielectric interlayers between the NBG perovskite and the metal back contact can reduce the plasmonic absorption losses. Texturing potentially allows to increase the current‐matched short‐circuit current density beyond 17 mA .

Chemical Synergic Stabilization of High Br-Content Mixed-Halide Wide-Bandgap Perovskites for Durable Multi-Terminal Tandem Solar Cells with Minimized Pb Leakage.

High Br-content mixed-halide perovskites with wide-bandgap (WBG) of 1.6-2.0 eV have showcased vast potential to be used in tandem solar cells. However, they often suffer from severe halide segregation, phase separation and ion migration issues, which would accelerate the decomposition of perovskites films,deteriorate the photovoltaic performance and even aggravate the lead leakage from damaged devices. Here, we report a novel chemical synergic interaction strategy to mitigate the abovementioned issues. A small amount of cationic β-cyclodextrin, composed of multiple ammonium cations, chlorine ions and abundant hydroxyl functional groups, was introduced into WBG perovskites, which effectively stabilized the halide ions and homogenized the phase distribution, comprehensively passivated the defects,and efficiently immobilized the Pb2+ ions. Encouragingly, the cationic β-cyclodextrin was universal and useful for different WBG perovskites, which favorably boosted the efficiencies by 10%-36% and extended the device operational stability to 2680 h. The integrated four-terminal orsix-terminal all-perovskite tandem solar cells exhibited efficiencies up to 24.39% and 22.42%, respectively. We demonstrated the cationic β-cyclodextrin-assisted internal chemical encapsulation effectively prevented the Pb leakage from severely damaged devices with only 5.63 ppb Pb leaching out. The target tandem solar cells with cationic β-cyclodextrin modification also realized a Pb sequestration efficiency of 93.4%.

Chemical Synergic Stabilization of High Br‐Content Mixed‐Halide Wide‐Bandgap Perovskites for Durable Multi‐Terminal Tandem Solar Cells with Minimized Pb Leakage

High Br‐content mixed‐halide perovskites with wide‐bandgap (WBG) of 1.6‐2.0 eV have showcased vast potential to be used in tandem solar cells. However, they often suffer from severe halide segregation, phase separation and ion migration issues, which would accelerate the decomposition of perovskites films, deteriorate the photovoltaic performance and even aggravate the lead leakage from damaged devices. Here, we report a novel chemical synergic interaction strategy to mitigate the abovementioned issues. A small amount of cationic β‐cyclodextrin, composed of multiple ammonium cations, chlorine ions and abundant hydroxyl functional groups, was introduced into WBG perovskites, which effectively stabilized the halide ions and homogenized the phase distribution, comprehensively passivated the defects,and efficiently immobilized the Pb2+ ions. Encouragingly, the cationic β‐cyclodextrin was universal and useful for different WBG perovskites, which favorably boosted the efficiencies by 10%‐36% and extended the device operational stability to 2680 h. The integrated four‐terminal or six‐terminal all‐perovskite tandem solar cells exhibited efficiencies up to 24.39% and 22.42%, respectively. We demonstrated the cationic β‐cyclodextrin‐assisted internal chemical encapsulation effectively prevented the Pb leakage from severely damaged devices with only 5.63 ppb Pb leaching out. The target tandem solar cells with cationic β‐cyclodextrin modification also realized a Pb sequestration efficiency of 93.4%.