JIALINGBO

Perovskite Solar Cells

In article number 2101590, Hongqiang Wang and co-workers report stable perovskite solar cells with champion efficiency over 24% and moisture (75%) stability over 10 000 hours. Referencing the Chinese story “Nezha Conquers the Dragon King”, the tower of perovskite is strengthened by the interfacial embedding of laser-manufactured fluorinated gold clusters.

Incorporation of the chromium-based metal–organic framework as an A-site cation allows realizing a new multiple-dimensional electronically coupled CsPbI₂Br perovskite, which is theoretically and experimentally proved to improve the carrier transport ability and stability of perovskite solar cells (PSCs). Consequently, the as-fabricated CsPbI₂Br PSCs demonstrate 17.02% power conversion efficiency while superior long-term stability.

Abstract

Inorganic CsPbI _x Br_{3− x} perovskite solar cells (PSCs) have gained enormous interest due to their excellent thermal stabilities. However, their intrinsically poor moisture stability hampers their further development. Herein, a chromium-based metal–organic framework group is intercalated inside the inorganic PbI framework, resulting in a new multiple-dimensional electronically coupled CsPbI₂Br perovskite. In this structurally and electronically coupled perovskite, the π-conjugated terpyridyl can delocalize the excited valence electrons of metal Cr³⁺ ion, enabling multi-interactive charge-carrier transport channels within CsPbI₂Br perovskites. The stability and efficiency of the produced devices are substantially enhanced in comparison to their counterparts with only a pristine CsPbI₂Br active layer. The optimized all-inorganic PSC yields a power conversion efficiency (PCE) as high as 17.02%. Remarkably, the stabilized device retains 80% of its PCE after 1000 h in the ambient atmosphere. This study provides a new paradigm toward addressing the stability challenge of the inorganic perovskite while enhancing its carrier transport ability.

A poling process that simultaneously modulates the built-in field and interface barriers of the perovskite solar cells has been conducted for the perovskite doped by P(VDF-TrFE). It has been unveiled that the new devices have achieved a high power conversion effectivity of 22.1%, attributed to the piezophototronic effect that effectively enhances the performance of the perovskite solar cell.

As a candidate for next-generation solar devices, perovskite solar cells are increasingly being studied for their rapid increased power conversion efficiency (PCE). One of the possible routes to further increase PCE is the introduction of polarization in the absorption layer which functions as a method for increasing the built-in potential and reducing the interface barrier, leading to much improved carrier separation and extraction. This technique uses the principle of the piezophototronic effect utilized for obtaining enhanced optoelectronic performances. Herein, to introduce internal polarization while maintaining optical absorption performance of the perovskite, organic–inorganic hybrid perovskite composite film solar cells are fabricated by doping polarized polyvinylidenefluoride-co-trifluoroethylene (P(VDF-TrFE)) into the perovskite. The composite film is polarized with an external potential, subsequently inducing the piezophototronic effect to enhance the performances of perovskite solar cells. Experimental results show that this simple polarization method has effectively improved several key characteristics of the solar cell. The PCE has reached up to 22.1%, the short-circuit current (J _sc) increases to 24.2 mA cm⁻², and the open-circuit voltage (V _oc) increases to 1.18 V.

A novel fullerene molecular template with a solubility enhancer arm (R1) and a π–π interaction inducer arm (R2) is deliberately proposed. This design effort delivers the highest power conversion efficiency over 20% of the device with corresponding fulleropyrrolidine electron transport material for the first time.

Abstract

[6,6]-phenyl-C₆₁-butyric acid methyl ester remains indispensable as the electron transport material (ETM) for perovskite solar cells (PSCs), but its synthesis involves complicated multisteps with low productivity. In contrast, the potential of synthesizing simpler fulleropyrrolidine derivatives has long been overlooked, and little has been understood regarding their structure-dependent effects on photovoltaic (PV) performance. Herein, seven novel fulleropyrrolidine derivatives (F1–F7) are deliberately designed, synthesized, and comprehensively characterized in both solution and thin-film states and subsequently investigated as ETMs for PSCs. Notably, the F4 delivers the highest power conversion efficiencies over 20% of devices, which surpass all reported fulleropyrrolidine ETMs due to its optimal photoelectric property. Moreover, the structure-dependent effects of the fullerenes on PV parameters are uncovered, including solubility, intermolecular interaction, packing structure, and charge-transfer ability, which can guide the future design of high-performance and stable fullerene ETMs for PSCs.

Gradual perovskite phase based on 2D cyclohexylmethylammonium iodide as the order of n and funnel-like energy level alignment during surface treatment with a simple solution process facilitates efficient charge transport electrically and improves power conversion efficiency from 20.41% to 23.91%.

Abstract

Insufficient charge extraction at the interfaces between light-absorbing perovskites and charge transporting layers is one of the drawbacks of state-of-the-art perovskite solar cells. Surface treatments and/or interface engineering are necessary to approach the Shockley–Queisser limit. In this work, novel 2D layered perovskites, such as CHA₂PbI₄ (CHAI = cyclohexylammonium iodide) and CHMA₂PbI₄ (CHMAI = cyclohexylmethylammonium iodide), are introduced in between 3D perovskites and hole transporting layers by a simple solution process and the 2D/3D perovskite heterojunction is formed and confirmed. Spontaneous photoluminescence quenching is observed by efficient hole extraction with a favorable valence band alignment. The charge extraction ability and recombination are directly measured by the transient photocurrent and photovoltage. Moreover, the interface resistance of the devices significantly is decreased to 30% as compared to devices without 2D perovskites. As a result, the devices with 2D/3D perovskite heterojunction exhibit improved power conversion efficiency (PCE) from 20.41% to 23.91% primarily because of the increased open-circuit voltage (1.079 to 1.143 V) and fill factor (78.22% to 84.25%). The results provide a detailed insight into hole extraction and high PCEs with the formation of a 2D/3D perovskite heterojunction.

A dual-additive strategy is developed to prepare quasi-core/shell-structure perovskite nanocrystals by using 18-crown-6 and poly(ethylene glycol) methyl ether acrylate as the additives. State-of-the-art external quantum efficiency of 28.1% and increased operating lifetime are achieved for the light-emitting diodes, owing to the synergetic effect for reduced defect density and improved environmental stability of the perovskite emissive layer.

Abstract

Quasi-2D perovskites have long been considered to have favorable “energy funnel/cascade” structures and excellent optical properties compared with their 3D counterparts. However, most quasi-2D perovskite light-emitting diodes (PeLEDs) exhibit high external quantum efficiency (EQE) but unsatisfactory operating stability due to Auger recombination induced by high current density. Herein, a synergetic dual-additive strategy is adopted to prepare perovskite films with low defect density and high environmental stability by using 18-crown-6 and poly(ethylene glycol) methyl ether acrylate (MPEG-MAA) as the additives. The dual additives containing COC bonds can not only effectively reduce the perovskite defects but also destroy the self-aggregation of organic ligands, inducing the formation of perovskite nanocrystals with quasi-core/shell structure. After thermal annealing, the MPEG-MAA with its CC bond can be polymerized to obtain a comb-like polymer, further protecting the passivated perovskite nanocrystals against water and oxygen. Finally, state-of-the-art green PeLEDs with a normal EQE of 25.2% and a maximum EQE of 28.1% are achieved, and the operating lifetime (T ₅₀) of the device in air environment is over ten times increased, providing a novel and effective strategy to make high efficiency and long operating lifetime PeLEDs.

The multi-scale defect repair strategy is developed to fabricate scalable and flexible perovskite solar cells. By inhibiting the aggregation behavior of colloidal particles to avoid pinholes and intergranular cracking in the perovskite film, along with repairing the deep defects at the interface, the target flexible devices (1.01 cm²) deliver a superior efficiency of 18.12% with improved air atmosphere stability.

Abstract

Homogeneity and stability of flexible perovskite solar cells (PSCs) are significant for the commercial feasibility in upscaling fabrication. Concretely, the mismatching between bottom interface and perovskite precursor ink can cause uncontrollable crystallization and undesired dangling bonds during the printing process. Herein, methylammonium acetate, serving as ink assistant (IAS) can effectively avoid the micron-scale defects of perovskite film. The in situ optical microscope is applied to prove the IAS can inhibit the colloidal aggregation and induce more adequate crystallization growth, thus avoiding the micron-scale defects of pinholes and intergranular cracking. Concurrently, 4-chlorobenzenesulfonic acid is introduced into the electrode surface as a passivation layer to restore the deep traps at perovskite interface in nano-scale. Finally, the target flexible devices (1.01 cm²) deliver a superior efficiency of 18.12% with improved air atmosphere stability. This multi-scale defect repair strategy provides an integrated design concept of homogeneity and stability for scalable and flexible PSCs.

Herein, a novel approach, a reactive post-treatment technique using guanidine acetate, to enhance the grain size and introduce a secondary phase simultaneously is applied in a perovskite interface. The enhanced grain size helps to reduce the defect densities at the grain boundaries, while the secondary phases make the perovskite surface more n-type, enhancing the device efficiency and stability.

Organic–inorganic lead halide perovskites (OIHPs) have emerged as promising materials for next-generation photovoltaics. However, performance improvements in the perovskite-based device are still limited due to defects that exist more intensively on the surface as well as grain boundaries (GBs) and mismatching energy levels at the interface. Herein, a reactive post-treatment process (RPP) using guanidine acetate (GA) is adopted to address defects and interfacial energy level matching at the perovskite surface. The RPP with GA (GA-RPP) results in the formation of an improved perovskite layer with large grain size and low GB density, leading to the formation of secondary phases on the perovskite surface with appropriate energy levels, resulting in reduced defect density and charge recombination. Furthermore, density functional theory analysis reveals that the Pb-rich secondary phase could improve the conduction of electrons at the perovskite interface. Therefore, the GA-RPP-based perovskite-based solar cell (PSC) shows enhanced performance with 20.4% efficiency and long-term stability.

Publication date: November 2021

Source: Nano Energy, Volume 89, Part B

Author(s): Aleksandra Furasova, Pavel Voroshilov, Mikhail Baranov, Pavel Tonkaev, Anna Nikolaeva, Kirill Voronin, Luigi Vesce, Sergey Makarov, Aldo Di Carlo

Hole-transport-layer (HTL) free tin perovskite solar cells would solve the stability issue caused by the unstable organic HTL. Formamidinium tin iodide doped with heterogeneous ammonium salts can form an upward band-bending structure to selectively extract the hole in the HTL-free cells. An efficiency of over 10% with reliable light-soaking and thermal stability can be achieved for the cells.

Abstract

Lead-free tin perovskite solar cells (PSCs) have emerged as a promising candidate toward high-performance and eco-friendly photovoltaic technology with great potential for future application. However, tin PSCs with over 10% efficiency usually feature an organic hole transport layer (HTL) at the illumination side that may induce device degradation during long-term operation. Removing the unstable organic HTL is an important way to solve these stability issues, but the efficiency of HTL-free tin PSCs is still much lower than that of the completed cells. Herein, it is demonstrated that formamidinium tin iodide doped with heterogeneous ammonium salts can form an upward band-bending structure to selectively extract the hole in the HTL-free devices. By using this band-bending structure, a promising efficiency of over 10% is first achieved for the lead-free PSCs with a HTL-free structure. More importantly, the optimized cell is highly stable, keeping 95% and 90% of the initial efficiency after continuous light soaking for 40 days and 80 °C annealing for 300 h, respectively. This work paves a route toward the development of efficient, eco-friendly, and highly stable perovskite photovoltaics.

Operationally stable mixed‐cation‐halide perovskite solar cells are fabricated by halogen‐engineering concept via a Br‐rich seeding growth method. Bromine anions are effectively incorporated into the final perovskite film with larger grains and better vertical columnar alignment. Photovoltaic devices based on the film show a power conversion efficiency (PCE) of 21.5% and significantly enhanced operational stability for over 500 h.

Abstract

The performance of perovskite solar cells (PSCs) relies on the synthesis method and chemical composition of the perovskite materials. So far, PSCs that have adopted two‐step sequential deposited perovskite with the state‐of‐art composition (FAPbI₃)_{1− x} (MAPbBr₃) _x (x < 0.05) have achieved record power conversion efficiency (PCE), while their one‐step antisolvent dripping counterparts with typical composition Cs_0.05FA_0.81MA_0.14Pb(I_0.85Br_0.15)₃ with more bromine have exhibited much better long‐term operational stability. Thus, halogen engineering that aims to elevate bromine content in sequential deposited perovskite film would push operational stability of PSCs toward that of antisolvent dripping deposited perovskite materials. Here, a Br‐rich seeding growth method is devised and perovskite seed solution with high bromine content is introduced into a PbI₂ precursor, leading to bromine incorporation in the resulting perovskite film. Photovoltaic devices fabricated by Br‐rich seeding growth method exhibit a PCE of 21.5%, similar to 21.6% for PSCs having lower bromine content. Whereas, the operational stability of PSCs with higher bromine content is significantly enhanced, with over 80% of initial PCE retained after 500 h tracking at maximum power point under 1‐sun illumination. This work highlights the vital importance of halogen composition for the operational stability of PSCs, and introduces an effective way to incorporate bromine into mixed‐cation‐halide perovskite film via sequential deposition method.

Research on compositional engineering can realize power conversion efficiency (PCE) over 25%. Interfacial engineering along with optimal perovskite solar cell device structure is expected to lead to stable and theoretical PCE over 30%.

Abstract

Discovery of the 9.7% efficiency, 500 h stable solid‐state perovskite solar cell (PSC) in 2012 triggered off a wave of perovskite photovoltaics. As a result, a certified power conversion efficiency (PCE) of 25.2% was recorded in 2019. Publications on PSCs have increased exponentially since 2012 and the total number of publications reached over 13 200 as of August 2019. PCE has improved by developing device structures from mesoscopic sensitization to planar p‐i‐n (or n‐i‐p) junction and by changing composition from MAPbI₃ to FAPbI₃‐based mixed cations and/or mixed anion perovskites. Long‐term stability has been significantly improved by interfacial engineering with hydrophobic materials or the 2D/3D concept. Although small area cells exhibit superb efficiency, scale‐up technology is required toward commercialization. In this review, research direction toward large‐area, stable, high efficiency PSCs is emphasized. For large‐area perovskite coating, a precursor solution is equally important as coating methods. Precursor engineering and formulation of the precursor solution are described. For hysteresis‐less, stable, and higher efficiency PSCs, interfacial engineering is one of the best ways as defects can be effectively passivated and thereby nonradiative recombination is efficiently reduced. Methodologies are introduced to minimize interfacial and grain boundary recombination.

An efficient interface passivation strategy for integrated perovskite/organic solar cells (IPOSCs) based on layered RP perovskite is demonstrated. The polymer PM6 is developed as the passivation layer to reduce the interface defects and suppress the nonradiation recombination in IPOSCs, leading to an improved V _OC from 1.06 to 1.12 V. The optimized IPOSC exhibits a champion efficiency of 19.15%, much higher than the control device (PCE = 16.33%).

Abstract

Integrated perovskite/organic solar cells (IPOSCs) have shown great potential in broadening the light absorption range and improving the photovoltaic performance. However, the severe interface charge recombination and unmatched energy levels between perovskite and organic photoactive layers hinder their performance improvement. Here, an efficient interface passivation strategy for IPOSCs based on a layered Ruddlesden–Popper (RP) perovskite and high photovoltaic performance is successfully demonstrated. It is found that an ultrathin conjugated polymer (PM6) layer could passivate the surface defects of perovskite film, tuning the energy level and suppress the nonradiative recombination loss, leading to efficient interface contact between RP perovskite and organic photoactive layers, boosting the open-circuit voltage from 1.06 to 1.12 V and the efficiency from 17.23% to 19.15%. Importantly, the optimized device shows extended photocurrent response to 930 nm with a peak intensity close to 50% from 800 to 931 nm. The results indicate that interface passivation using a functionalized polymer could be an efficient strategy to improve the photovoltaic performance of integrated devices.

A residual charge testing approach is used to investigate the trapping and detrapping process in the perovskite solar cells based on the active layers with different crystallization and the morphology. The results reveal that the residual charge exists widely at the grain boundary, and the residual charge is related to the performance of the perovskite solar cells.

Abstract

The performance of perovskite solar cells is greatly affected by the crystallization of the perovskite active layer. Perovskite crystal grains should neatly arrange and penetrate the entire active layer for an ideal perovskite crystallization. These kinds of crystallized perovskite films exhibit fewer defects and longer carrier lifetime, which is beneficial to enhance the performance of perovskite solar cells. Here, by testing the residual charge of perovskite solar cells with different crystallization conditions, it is demonstrated that the residual charge exists widely at the grain boundary, which is parallel to the device, and the residual charge is related to the performance of the perovskite solar cells. Single crystal grains neatly arranged and penetrate the entire active layer can generate less residual charge and improve device performance of the perovskite solar cells. The results also show that the long decay time of open-circuit voltage comes from the detrapping of trapped carriers. The residual charge testing technology provides a new idea for the investigation of carrier trap and detrap characteristics in photovoltaic devices.

N719 dye molecules effectively link nickel oxide (NiO _x )/perovskite interfaces by facilitating charge transport, concurrently passivating NiO _x and perovskite surface traps, and forming a barrier that prevents undesirable chemical reactions occurring at the interface. The molecule also self-anchors and conformally covers NiO _x films deposited on complex surfaces, enabling fabrication of highly efficient textured monolithic p-i-n perovskite/silicon tandem solar cells.

Abstract

Sputtered nickel oxide (NiO _x ) is an attractive hole-transport layer for efficient, stable, and large-area p-i-n metal-halide perovskite solar cells (PSCs). However, surface traps and undesirable chemical reactions at the NiO _x /perovskite interface are limiting the performance of NiO _x -based PSCs. To address these issues simultaneously, an efficient NiO _x /perovskite interface passivation strategy by using an organometallic dye molecule (N719) is reported. This molecule concurrently passivates NiO _x and perovskite surface traps, and facilitates charge transport. Consequently, the power conversion efficiency (PCE) of single-junction p-i-n PSCs increases from 17.3% to 20.4% (the highest reported value for sputtered-NiO _x based PSCs). Notably, the N719 molecule self-anchors and conformally covers NiO _x films deposited on complex surfaces. This enables highly efficient textured monolithic p-i-n perovskite/silicon tandem solar cells, reaching PCEs up to 26.2% (23.5% without dye passivation) with a high processing yield. The N719 layer also forms a barrier that prevents undesirable chemical reactions at the NiO _x /perovskite interface, significantly improving device stability. These findings provide critical insights for improved passivation of the NiO _x /perovskite interface, and the fabrication of highly efficient, robust, and large-area perovskite-based optoelectronic devices.

Genetic modification of M13 bacteriophages amplifies amino acid K, which functions as a perovskite growth template and a stronger passivator than the wild-type virus in PSCs. The modified virus-added PSCs exhibit a higher PCE (23.6%) than wild-type M13 virus-added devices (22.8%). The observed enhancement is attributed to slightly larger perovskite grains, stronger grain boundary passivation, and improved hole conductivity.

Abstract

Perovskite solar cells (PSCs) are considered to be one of the most promising solar energy harvesters owing to their high power conversion efficiency (PCE). To increase their PCE even further, additives are used; however, some of these additives pose certain disadvantages, which limit their applications to PSCs. Therefore, in this study, the nature-inspired ecofriendly M13 bacteriophage is genetically engineered to maximize its performance as a perovskite crystal growth template and as a passivator for PSCs. The genetic manipulation of the M13 bacteriophage enhances the Lewis coordination between the perovskite materials and single-stranded virus by amplifying a designated amino acid group. Among the 20 types of amino acids, lysine (Lys or K), arginine (Arg or R), and methionine (Aug or M) exhibit the strongest interaction with the perovskite materials. Results suggest that the K-amplified genetically engineered M13 bacteriophage is the most effective. The K-type M13 virus-inoculated PSCs yield a PCE of 23.6% in the laboratory. This device, when taken to a national laboratory for verification, exhibits a certified forward and reverse bias-combined efficiency (22.3%), which, to the best of the authors’ knowledge, is one of the highest efficiencies reported among the biomaterial-based PSCs.

This Minireview summarizes the recent developments on interfaces in inorganic perovskite solar cells, with special focus on the fundamental understanding of how interfaces influence the performance of devices. Directions for developing highly efficient and stable inorganic perovskite solar cells by interface engineering are also provided.

Abstract

Owing to their superior thermal stability, metal halide inorganic perovskite materials continue to attract interest for photovoltaics applications. The highest reported power conversion efficiency (PCE) for solar cells based on inorganic perovskites is over 20 %. As this PCE corresponds to 73 % of the theoretical limit, there remains more room for further improving the device PCEs than for improving organic–inorganic hybrid perovskite solar cells (PSCs). The main loss is in the photovoltage, which is limited by interfaces in terms of non-radiative recombination caused by traps and energy-level mismatch. Furthermore, inefficient charge extraction at interfacial contacts reduces the photocurrent and fill factor. This Minireview summarizes the recent developments in the fundamental understanding of how the interfaces and interfacial layers influence the performance of solar cells based on inorganic perovskite absorbers. An outlook for the development of highly efficient and stable inorganic PSCs from the interface point of view is also given.

Publication date: November 2021

Source: Nano Energy, Volume 89, Part B

Author(s): Yingchun Niu, Chen Tian, Jiajia Gao, Fan Fan, Yida Zhang, Yuanyuan Mi, Xiangcheng Ouyang, Lina Li, Jiapeng Li, Siyuan Chen, Yinping Liu, Hong-Liang Lu, Xuelin Zhao, Lifeng Yang, Huanxin Ju, Yingguo Yang, Chuan-Fan Ding, Meng Xu, Quan Xu

Unique hetero-structured CsPbI₃/CaF₂ perovskite/fluoride nanocomposites are constructed for fabricating efficient and ultra-stable perovskite solar cells (PSCs). The PSC device based on CsPbI₃/CaF₂-deposited Cs_0.05FA_0.81MA_0.14PbI_2.55Br_0.45 thin-film yields a best power conversion efficiency (PCE) of 21.06% and can retain 85% of its original PCE after 1000 h of continuous operation at the maximum power point tracking under AM 1.5G illumination.

Abstract

Organic-inorganic hybrid perovskite solar cells (PSCs) have rapidly developed over the past decade and have achieved the latest certified power conversion efficiency (PCE) up to 25.5%. However, unsatisfactory long-term operational stability for these hybrid PSCs remains a huge obstacle to further development and commercialization. Herein, a unique hetero-structured CsPbI₃/CaF₂ perovskite/fluoride nanocomposites (PFNCs) is fabricated via a newly developed facile two-step hetero-epitaxial growth strategy to deliver efficient and ultra-stable PSCs. After being incorporated into the crystal lattice of α-phase CsPbI₃ perovskite, the cubic-phase CaF₂ in the resultant CsPbI₃/CaF₂ PFNCs can not only passivate the intrinsic defects of CsPbI₃ perovskite itself but also effectively suppress the notorious ion migration in hybrid perovskite Cs_0.05FA_0.81MA_0.14PbI_2.55Br_0.45 (CsFAMA) thin-films of PSCs. As such, the CsFAMA PSC devices based on CsPbI₃/CaF₂-deposited perovskite thin-film achieve a mean PCE of 20.45%, in sharp contrast to 19.33% of the control devices without deposition. Specifically, the CsPbI₃/CaF₂-deposited PSC retains 85% of its original PCE after 1000 h continuous operation at the maximum power point under AM 1.5G solar light, far better than those of the control and CsPbI₃-deposited PSCs with a device T ₈₅ lifetime of 315 and 125 h, respectively.

Nickel oxide (NiO _x ) nanoparticles with high crystallinity and good dispersibility by the polymer network micro-precipitation method is synthesized, and the colloidal solution of ionic liquid-assisted NiO _x NPs dispersion is used to fabricate high-quality NiO _x films. Ultimately, the 1.01 cm² perovskite devices with the optimized NiO _x layers achieve the champion power conversion efficiency of 20.91% and 19.17% on rigid and flexible substrates, respectively.

Abstract

As one of the most promising hole transport layers (HTLs), nickel oxide (NiO _x ) has received extensive attention due to its application in flexible large-area perovskite solar cells (PSCs). However, the poor interface contact caused by inherent easy-agglomeration phenomenon of NiO _x nanoparticles (NPs) is still the bottleneck for achieving high-performance devices. Herein, a general strategy to synthesize NiO _x NPs with high crystallinity and good dispersibility via the polymer network micro-precipitation method is reported. Promisingly, this approach realizes the flow-division of precipitant and the restraint of the NPs motion, thereby effectively alleviating the coagulation phenomenon caused by excessive local concentration and secondary movement adsorption. Furthermore, the addition of ionic liquid not only inhibits the secondary aggregation of NiO _x NPs during the dispersion process, but also significantly enhances the properties of the colloidal solution. Ultimately, the 1.01 cm² PSCs based on the optimized NiO _x HTLs achieve the champion power conversion efficiency of 20.91% and 19.17% on rigid and flexible substrates, respectively. Moreover, the reproducibility and stability of PSCs are also significantly improved, especially for flexible devices. Overall, this strategy provides the possibility for flexible, large-area fabrication of high-quality NiO _x HTLs to promote the development of stable and efficient perovskite devices.