20.67%-Efficiency Inorganic CsPbI3 Solar Cells Enabled by Zwitterion Ion Interface Treatment

All-inorganic CsPbI₃ perovskite solar cells (PSCs) have been extensively studied due to their high thermal stability and unprecedented rise in power conversion efficiency (PCE). Recently, the champion PCE of CsPbI₃ PSCs has reached up to 21%; however, it is still much lower than that of organic–inorganic hybrid PSCs. Interface modification to passivate surface defects and minimize charge recombination and trapping is important to further improve the efficiency of CsPbI₃ PSCs. Herein, a new zwitterion ion is deposited at the interface between electron transporting layer (ETL) and perovskite layer to passivate the defects therein. The zwitterion ions can not only passivate oxygen vacancy (V_O) and iodine vacancy (V_I) defects, but also improve the band alignment at the ETL-perovskite interface. After the interface treatment, the PCE of CsPbI₃ device reaches up to 20.67%, which is among the highest values of CsPbI₃ PSCs so far. Due to the defect passivation and hydrophobicity improvement, the PCE of optimized device remains 94% of its original value after 800 h storing under ambient condition. These results provide an efficient way to improve the quality of ETL-perovskite interface by zwitterion ions for achieving high performance inorganic CsPbI₃ PSCs.     

Highly Efficient p‐i‐n Perovskite Solar Cells Utilizing Novel Low‐Temperature Solution‐Processed Hole Transport Materials with Linear π‐Conjugated Structure

Alternative low‐temperature solution‐processed hole‐transporting materials (HTMs) without dopant are critical for highly efficient perovskite solar cells (PSCs). Here, two novel small molecule HTMs with linear π‐conjugated structure, 4,4′‐bis(4‐(di‐p‐toyl)aminostyryl)biphenyl (TPASBP) and 1,4′‐bis(4‐(di‐p‐toyl)aminostyryl)benzene (TPASB), are applied as hole‐transporting layer (HTL) by low‐temperature (sub‐100 °C) solution‐processed method in p‐i‐n PSCs. Compared with standard poly(3,4‐ethylenedioxythiophene): poly(styrenesulfonic acid) (PEDOT:PSS) HTL, both TPASBP and TPASB HTLs can promote the growth of perovskite (CH₃NH₃PbI₃) film consisting of large grains and less grain boundaries. Furthermore, the hole extraction at HTL/CH₃NH₃PbI₃ interface and the hole transport in HTL are also more efficient under the conditions of using TPASBP or TPASB as HTL. Hence, the photovoltaic performance of the PSCs is dramatically enhanced, leading to the high efficiencies of 17.4% and 17.6% for the PSCs using TPASBP and TPASB as HTL, respectively, which are ≈40% higher than that of the standard PSC using PEDOT:PSS HTL.     

Graded Heterojunction Engineering for Hole‐Conductor‐Free Perovskite Solar Cells with High Hole Extraction Efficiency and Conductivity

Despite great progress in the photovoltaic conversion efficiency (PCE) of inorganic–organic hybrid perovskite solar cells (PSCs), the large‐scale application of PSCs still faces serious challenges due to the poor‐stability and high‐cost of the spiro‐OMeTAD hole transport layer (HTL). It is of great fundamental importance to rationally address the issues of hole extraction and transfer arising from HTL‐free PSCs. Herein, a brand‐new PSC architecture is designed by introducing multigraded‐heterojunction (GHJ) inorganic perovskite CsPbBr_x I_3?x layers as an efficient HTL. The grade adjustment can be achieved by precisely tuning the halide proportion and distribution in the CsPbBr_x I_3?x film to reach an optimal energy alignment of the valance and conduction band between MAPbI₃ and CsPbBr_x I_3?x . The CsPbBr_x I_3?x GHJ as an efficient HTL can induce an electric field where a valance/conduction band edge is leveraged to bend at the heterojunction interface, boosting the interfacial electron–hole splitting and photoelectron extraction. The GHJ architecture enhances the hole extraction and conduction efficiency from the MAPbI₃ to the counter electrode, decreases the recombination loss during the hole transfer, and benefits in increasing the open‐circuit voltage. The optimized HTL‐free PCS based on the GHJ architecture demonstrates an outstanding thermal stability and a significantly improved PCE of 11.33%, nearly 40% increase compared with 8.16% for pure HTL‐free devices.     

Advances in cesium lead iodide perovskite solar cells: Processing science matters

The prevailing perovskite solar cells (PSCs) employ hybrid organic–inorganic halide perovskites as light absorbers, but these materials exhibit relatively poor environmental stability, which potentially hinders the practical deployment of PSCs. One important strategy to address this issue is replacing the volatile and hygroscopic organic cations with inorganic cesium cations in the crystal structure, forming all-inorganic halide perovskites. In this context, CsPbI₃ perovskite is drawing phenomenal attention, primarily because it exhibits an ideal bandgap of 1.7 eV for the use in tandem solar cells, and it shows significantly enhanced thermal stability that is the key to the long-term device operation. Within only half a decade, the power conversion efficiency (PCE) of CsPbI₃ PSCs has ramped beyond 20%, which has been driven by inventions of numerous processing methods for high-quality CsPbI₃ perovskite thin films. These methods are broadly classified into three categories: vapor deposition, nanocrystals assembly, and solution deposition. Herein we present a systematic review on these methods and related materials sciences. In particular, we comprehensively discuss the dimethylammonium-additive-based solution deposition, which has resulted into the best-performing CsPbI₃ PSCs. We also present the challenges and prospects on future research towards the realization of the full potential of CsPbI₃ PSCs.     

Efficient and Stable CsPbI3 Solar Cells via Regulating Lattice Distortion with Surface Organic Terminal Groups

All‐inorganic cesium lead iodide perovskites (CsPbI₃) are promising wide‐bandgap materials for use in the perovskite/silicon tandem solar cells, but they easily undergo a phase transition from a cubic black phase to an orthorhombic yellow phase under ambient conditions. It is shown that this phase transition is triggered by moisture that causes distortion of the corner‐sharing octahedral framework ([PbI₆]^4?). Here, a novel strategy to suppress the octahedral tilting of [PbI₆]^4? units in cubic CsPbI₃ by systematically controlling the steric hindrance of surface organic terminal groups is provided. This steric hindrance effectively prevents the lattice distortion and thus increases the energy barrier for phase transition. This mechanism is verified by X‐ray diffraction measurements and density functional theory calculations. Meanwhile, the formation of an organic capping layer can also passivate the surface electronic trap states of perovskite absorber. These modifications contribute to a stable power conversion efficiency (PCE) of 13.2% for the inverted planar perovskite solar cells (PSCs), which is the highest efficiency achieved by the inverted‐structure inorganic PSCs. More importantly, the optimized devices retained 85% of their initial PCE after aging under ambient conditions for 30 days.     

倒置钙钛矿太阳能电池的空穴传输层的研究进展

倒置钙钛矿太阳能电池(PSCs)具有器件结构简单、吸光系数高、迟滞效应小、良好的缺陷容忍性等优点,受到了广泛的关注。但倒置器件光电转换效率(PCE)尚有待提高,究其原因是空穴传输层(HTL)和钙钛矿层界面处的能量损失表现出相对较小的开路电压。文章综述了包括有机聚合物、无机物、尖晶石氧化物等作为空穴传输材料的相关研究进展,进一步分析了通过调节电极/空穴传输层能级使之与钙钛矿价带匹配,及通过界面修饰促进器件对载流子的注入与收集,从而提高光电转换效率的研究现状。对提高倒置钙钛矿太阳能电池性能的研究具有一定的指导意义,最后对倒置器件的应用前景进行了展望。     

Defect‐Engineering‐Enabled High‐Efficiency All‐Inorganic Perovskite Solar Cells

The emergence of cesium lead iodide (CsPbI₃) perovskite solar cells (PSCs) has generated enormous interest in the photovoltaic research community. However, in general they exhibit low power conversion efficiencies (PCEs) because of the existence of defects. A new all‐inorganic perovskite material, CsPbI₃:Br:InI₃, is prepared by defect engineering of CsPbI₃. This new perovskite retains the same bandgap as CsPbI₃, while the intrinsic defect concentration is largely suppressed. Moreover, it can be prepared in an extremely high humidity atmosphere and thus a glovebox is not required. By completely eliminating the labile and expensive components in traditional PSCs, the all‐inorganic PSCs based on CsPbI₃:Br:InI₃ and carbon electrode exhibit PCE and open‐circuit voltage as high as 12.04% and 1.20 V, respectively. More importantly, they demonstrate excellent stability in air for more than two months, while those based on CsPbI₃ can survive only a few days in air. The progress reported represents a major leap for all‐inorganic PSCs and paves the way for their further exploration in order to achieve higher performance.     

Synergistic Ionic Liquid in Hole Transport Layers for Highly Stable and Efficient Perovskite Solar Cells

Perovskite solar cells (PSCs) with n-i-p structures often utilize an organic 2,2′,7,7′-tetrakis (N, N-di-p-methoxyphenyl-amine) 9,9′-spirobifluorene (spiro-OMeTAD) along with additives of lithium bis(trifluoromethanesulfonyl)imide salt (LiTFSI) and tert-butylpyridine as the hole transporting layer (HTL). However, the HTL lacks stability in ambient air, and numerous defects are often present on the perovskite surface, which is not conducive to a stable and efficient PSC. Therefore, constructive strategies that simultaneously stabilize spiro-OMeTAD and passivate the perovskite surface are required. In this work, it is demonstrated that a novel ionic liquid of dimethylammonium bis(trifluoromethanesulfonyl)imide (DMATFSI) could act as a bifunctional HTL modulator in n-i-p PSCs. The addition of DMATFSI into spiro-OMeTAD can effectively stabilize the oxidized spiro-OMeTAD⁺ cation radicals through the formation of spiro-OMeTAD⁺TFSI⁻ because of the excellent charge delocalization of the conjugated CF₃SO₂⁻ moiety within TFSI⁻. In addition, DMA⁺ cations could move toward the perovskite from the HTL, resulting in the passivation of defects at the perovskite surface. Accordingly, a power conversion efficiency of 23.22% is achieved for PSCs with DMATFSI and LiTFSI co-doped spiro-OMeTAD. Moreover, benefiting from the improved ion migration barrier and hydrophobicity of the HTL, still retained nearly 80% of their initial power conversion efficiency after 36 days of exposure to ambient air.     

High-Efficiency Carbon-based CsPbI2Br Perovskite Solar Cells from Dual Direction Thermal Diffusion Treatment with Cadmium Halides

In recent years, carbon-based CsPbI₂Br perovskite solar cells (PSCs) have attracted more attention due to their low cost and good stability. However, the power conversion efficiency (PCE) of carbon-based CsPbI₂Br PSCs is still no more than 16%, because of the defects in CsPbI₂Br or at the interface with the electron transport layer (ETL), as well as the energy level mismatch, which lead to the loss of energy, thus limiting PCE values. Herein, a series of cadmium halides are introduced, including CdCl₂, CdBr₂ and CdI₂ for dual direction thermal diffusion treatment. Some Cd²⁺ ions thermally diffuse downward to passivate the defects inside or on the surface of SnO₂ ETL. Meanwhile, the energy level structure of SnO₂ ETL is adjusted, which is in favor of the transfer of electron carriers and blocking holes. On the other hand, part of Cd²⁺ and Cl⁻ ions thermally diffuse upward into the CsPbI₂Br lattice to passivate crystal defects. Through dual direction thermal diffusion treatment by CdCl₂, CdI₂ and CdBr₂, the performance of devices has been significantly improved, and their PCE has been increased from 13.01% of the original device to 14.47%, 14.31%, and 13.46%, respectively. According to existing reports, 14.47% is one of the highest PCE of carbon-based CsPbI₂Br PSCs with SnO₂ ETLs.     

Morphology Control of Doped Spiro‐MeOTAD Films for Air Stable Perovskite Solar Cells

Doped 2,2′,7,7′‐tetrakis(N,N‐di‐p‐methoxyphenylamine)‐9,9′‐spirobifluorene (spiro‐MeOTAD), which acts as a hole‐transporting layer (HTL), endows perovskite solar cells (PSCs) with excellent performance. However, the intrinsically hygroscopic nature of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) dopants also aggravates the moisture instability of PSCs. In this work, the origins of the moisture instability of spiro‐MeOTAD HTLs are explored and strategies to enhance moisture resistance are proposed. After 780 h of aging in air, 52% of the initial power conversion efficiency (PCE) can be sustained by prolonging the mixing time of the precursor solution of spiro‐MeOTAD to reduce accumulated LiTFSI. In contrast, only 7% of the initial PCE remains if the precursor solution is mixed briefly. By thermally annealing an HTL to evaporate residual tBP in spiro‐MeOTAD, pinholes are completely eliminated and 65% of the initial PCE remains after the same aging time. In this study, the significance of the initial morphology of spiro‐MeOTAD HTLs on device stability is analyzed and strategies based on physical morphology for controlling PSC moisture instability induced by HTL dopants are developed.     

Nanoporous p-type NiOx electrode for p-i-n inverted perovskite solar cell toward air stability

Designing air-stable perovskite solar cells (PSCs) is a recent trend in low-cost photovoltaic technology. Metal oxide-based electron transporting layers (ETLs) and hole transporting layers (HTLs) have attracted tremendous attention in PSCs, because of their excellent air stability, high electron mobility, and optical transparency. Herein, we report a co-precipitation method for the synthesis of p-type nanoporous nickel oxide (np-NiOx) thin films as the HTL for inverted (p-i-n) PSCs. The best-performing p-i-n PSC having np-NiOx HTL, (FAPbI₃)_0.85(MAPbBr₃)_0.15 (herein FAPbI₃ stands for formamidinium lead iodide and MAPbBr₃ stands for methylammonium lead bromide) perovskite and phenyl-C₆₁-butyric acid methyl ester (PCBM)/ZnO ETL exhibited a 19.10% (±1%) power conversion efficiency (PCE) with a current density (J_SC) of 22.76?mA?cm^?2, open circuit voltage (V_OC) of 1.076?V and fill factor (FF) of 0.78 under 1?sun (100?mW?cm^?2). Interestingly, the developed p-i-n PSCs based on p-type NiOx and n-type ZnO could retain >80% efficiency after 160?days, which is much higher than conventional PEDOT:PSS HTL-based PSCs. Our findings provide air-stable perovskite solar cells with high efficiency.     

Molecule‐Doped Nickel Oxide: Verified Charge Transfer and Planar Inverted Mixed Cation Perovskite Solar Cell

Both conductivity and mobility are essential to charge transfer by carrier transport layers (CTLs) in perovskite solar cells (PSCs). The defects derived from generally used ionic doping method lead to the degradation of carrier mobility and parasite recombinations. In this work, a novel molecular doping of NiO_x hole transport layer (HTL) is realized successfully by 2,2′‐(perfluoronaphthalene‐2,6‐diylidene)dimalononitrile (F6TCNNQ). Determined by X‐ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy, the Fermi level (E_F) of NiO_x HTLs is increased from ?4.63 to ?5.07 eV and valence band maximum (VBM)‐E_F declines from 0.58 to 0.29 eV after F6TCNNQ doping. The energy level offset between the VBMs of NiO_x and perovskites declines from 0.18 to 0.04 eV. Combining with first‐principle calculations, electrostatic force microscopy is applied for the first time to verify direct electron transfer from NiO_x to F6TCNNQ. The average power conversion efficiency of CsFAMA mixed cation PSCs is boosted by ≈8% depending on F6TCNNQ‐doped NiOx HTLs. Strikingly, the champion cell conversion efficiency of CsFAMA mixed cations and MAPbI₃‐based devices gets to 20.86% and 19.75%, respectively. Different from passivation effect, the results offer an extremely promising molecular doping method for inorganic CTLs in PSCs. This methodology definitely paves a novel way to modulate the doping in hybrid electronics more than perovskite and organic solar cells.     

Dimensional Tuning of Perylene Diimide-Based Polymers for Perovskite Solar Cells with Over 24% Efficiency

The hygroscopic dopants used in Spiro-OMeTAD hole transport material (HTM) in state-of-the-art perovskite solar cells (PSCs) inevitably induce premature degradation of the devices. Here, two multifunctional polymer interface materials based on the perylene diimides (PDI) unit are developed. It is found that quasi-two-dimensional (2D) polymer 2DP-PDI can form a denser film and exhibit better hydrophobicity than linear polymer P-PDI. Importantly, 2DP-PDI can passivate the surface defects and extract hole carriers of perovskite film more effectively, leading to much reduced nonradiative recombination loss. With polymer interface material between the perovskite and HTM layers, the optimized device using 2DP-PDI and P-PDI yields a champion PCE of 24.20% and 23.09%, respectively, along with significantly improved stability, whereas the control device shows a lower efficiency of 22.23%. These results suggest that developing multifunctional polymer interface materials can be a promising strategy to improve the efficiency and stability of PSCs.     

Surface modified NiOx as an efficient hole transport layer in inverted perovskite solar cells

Hole transporting materials play a vital role in improving the performance of perovskite solar cells (PSCs). In this work, different concentrations of poly[bis(4-phenyl)(2, 4, 6-trimethylphenyl)amine] (PTAA) are used to modify the surface of sputtered nickel oxide (NiO_x) as hole transport layer (HTL) in inverted PSCs. After the introduction of PTAA, the roughness of the sputtered NiO_x films decreases, while the crystallinity of the perovskite layer increases. The carrier transport across the interface between the sputtered NiO_x film and the perovskite layer is significantly improved. A power conversion efficiency of 18.5% is achieved based on PTAA-modified sputtered NiO_x, exhibiting a 15.2% improvement compared to its pristine counterpart.

     

Tailoring C60 for Efficient Inorganic CsPbI2Br Perovskite Solar Cells and Modules

Although inorganic perovskite solar cells (PSCs) are promising in thermal stability, their large open-circuit voltage (V_OC) deficit and difficulty in large-area preparation still limit their development toward commercialization. The present work tailors C₆₀ via a codoping strategy to construct an efficient electron-transporting layer (ETL), leading to a significant improvement in V_OC of the inverted inorganic CsPbI₂Br PSC. Specifically, tris(pentafluorophenyl)borane (TPFPB) is introduced as a dopant to lower the lowest unoccupied molecular orbital (LUMO) level of the C₆₀ layer by forming a Lewis acidic adduct. The enlarged free energy difference provides a favorable enhancement in electron injection and thereby reduces charge recombination. Subsequently, a nonhygroscopic lithium salt (LiClO₄) is added to increase electron mobility and conductivity of the film, leading to a reduction in the device hysteresis and facilitating the fabrication of a large-area device. Finally, the as-optimized inorganic CsPbI₂Br PSCs gain a champion power conversion efficiency (PCE) of 15.19%, with a stabilized power output (SPO) of 14.21% (0.09 cm²). More importantly, this work also demonstrates a record PCE of 14.44% for large-area inorganic CsPbI₂Br PSCs (1.0 cm²) and reports the first inorganic perovskite solar module with the excellent efficiency exceeding 12% (10.92 cm²) by a self-developed quasi-curved heating method.     

Highly Efficient and Stable Flexible Perovskite Solar Cells with Metal Oxides Nanoparticle Charge Extraction Layers

In this study, the fabrication of highly efficient and durable flexible inverted perovskite solar cells (PSCs) is reported. Presynthesized, solution‐derived NiO_x and ZnO nanoparticles films are employed at room temperature as a hole transport layer (HTL) and electron transport layer (ETL), respectively. The triple cation perovskite films are produced in a single step and for the sake of comparison, ultrasmooth and pinhole‐free absorbing layers are also fabricated using MAPbI₃ perovskite. The triple cation perovskite cells exhibit champion power conversion efficiencies (PCEs) of 18.6% with high stabilized power conversion efficiency of 17.7% on rigid glass/indium tin oxide (ITO) substrates (comparing with 16.6% PCE with 16.1% stabilized output efficiency for the flexible polyethylene naphthalate (PEN)/thin film barrier/ITO substrates). More interestingly, the durability of flexible PSC under simulation of operative condition is proved. Over 85% of the maximum stabilized output efficiency is retained after 1000 h aging employing a thin MAPbI₃ perovskite (over 90% after 500 h with a thick triple cation perovskite). This result is comparable to a similar state of the art rigid PSC and represents a breakthrough in the stability of flexible PSC using ETLs and HTLs compatible with roll to roll production speed, thanks to their room temperature processing.     

Highly π-extended copolymer as additive-free hole-transport material for perovskite solar cells

Organolead halide perovskite solar cells have achieved a certified power-conversion efficiency (PCE) of 22.1% and are thus among the most promising candidates for next-generation photovoltaic devices. To date, most high-efficiency perovskite solar cells have employed arylamine-based hole-transport materials (HTMs), which are expensive and have a low mobility. The complicated doping procedures and the potentially stability-adverse dopants used in these HTMs are among the major bottlenecks for the commercialization of perovskite solar cells (PSCs). Herein, we present a polythiophene-based copolymer (PDVT-10) with a hole mobility up to 8.2 cm²·V^?1·s^?1 and a highest occupied molecular orbital level of ?5.28 eV as a hole-transport layer (HTL) for a PSC. A device based on this new HTM exhibited a high PCE of 13.4% under 100 mW·cm^?2 illumination, which is one of the highest PCEs reported for the dopant-free polymer-based HTLs. Moreover, PDVT-10 exhibited good solution processability, decent air stability, and thermal stability, making it a promising candidate as an HTM for PSCs.

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Suppressing Excess Lead Iodide Aggregation and Reducing N-Type Doping at Perovskite/HTL Interface for Efficient Perovskite Solar Cells

Excess lead iodide (PbI₂) aggregation at the charge carrier transport interface leads to energy loss and acts as unstable origins in perovskite solar cells (PSCs). Here, a strategy is reported to modulate the interfacial excess PbI₂ by introducing π-conjugated small-molecule semiconductors 4,4'-cyclohexylbis[N,N-bis(4-methylphenyl)aniline] (TAPC) into perovskite films through an antisolvent addition method. The coordination of TAPC to Pb I units through the electron-donating triphenylamine groups and π-Pb²⁺ interactions allows for a compact perovskite film with reduced excess PbI₂ aggregates. Besides, preferred energy level alignment is achieved due to the suppressed n-type doping effect at the hole transport layer (HTL) interfaces. As a result, the TAPC-modified PSC based on Cs_0.05(FA_0.85MA_0.15)_0.95Pb(I_0.85Br_0.15)₃ triple-cation perovskite achieved an improved PCE from 18.37% to 20.68% and retained ≈90% of the initial efficiency after 30 days of aging under ambient conditions. Moreover, the TAPC-modified device based on FA_0.95MA_0.05PbI_2.85Br_0.15 perovskite produced an improved efficiency of 23.15% compared to the control (21.19%). These results provide an effective strategy for improving the performance of PbI₂-rich PSCs.     

Improved performance and reproducibility of perovskite solar cells by jointly tuning the hole transport layer and the perovskite layer deposition

Solution processed organometal trihalide materials spur tremendous attention due to their unprecedented performance in photovoltaic applications. However, submicron thick perovskite films are prone to morphological defects in the form of cracks, pinholes and porosity; the traits originated from their solution phase processing and subsequent crystallization. Moreover, pinholes and cracks in the thin film of spincoated Spiro-OMeTAD hole transport layer reduce the performance reliability by forming micro shorts and weaken the defense against moisture ingress to the perovskite layer. For the large scale processing of perovskite solar cell from the economically prudent solution phase processing, morphological shortcomings of both perovskite and hole transport layers need an urgent address. By selecting non-conventional lead precursor (lead acetate) and implementing anti-solvent treatment during film deposition, we able to form pinhole free and compact perovskite film. Crack free hole conducting layer is obtained by blending Spiro-OMeTAD with a conducting polymer without compromising in the solar cell performance. A detail investigation of the charge transport and charge extraction properties of the developed hole transport layers have been carried out. The developed CH₃NH₃PbI₃ based perovskite solar cells show improved repeatability and performance.     

Highly Efficient and Stable GABr-Modified Ideal-Bandgap (1.35 eV) Sn/Pb Perovskite Solar Cells Achieve 20.63% Efficiency with a Record Small Voc Deficit of 0.33 V

1.5–1.6 eV bandgap Pb-based perovskite solar cells (PSCs) with 30–31% theoretical efficiency limit by the Shockley–Queisser model achieve 21–24% power conversion efficiencies (PCEs). However, the best PCEs of reported ideal-bandgap (1.3–1.4 eV) Sn–Pb PSCs with a higher 33% theoretical efficiency limit are <18%, mainly because of their large open-circuit voltage (V_oc) deficits (>0.4 V). Herein, it is found that the addition of guanidinium bromide (GABr) can significantly improve the structural and photoelectric characteristics of ideal-bandgap (≈1.34 eV) Sn–Pb perovskite films. GABr introduced in the perovskite films can efficiently reduce the high defect density caused by Sn²⁺ oxidation in the perovskite, which is favorable for facilitating hole transport, decreasing charge-carrier recombination, and reducing the V_oc deficit. Therefore, the best PCE of 20.63% with a certificated efficiency of 19.8% is achieved in 1.35 eV PSCs, along with a record small V_oc deficit of 0.33 V, which is the highest PCE among all values reported to date for ideal-bandgap Sn–Pb PSCs. Moreover, the GABr-modified PSCs exhibit significantly improved environmental and thermal stability. This work represents a noteworthy step toward the fabrication of efficient and stable ideal-bandgap PSCs.