Defects In Perovskites Research Articles

Freezing Halide Segregation Under Intense Light for Photostable Perovskite/Silicon Tandem Solar Cells

AbstractPhoto‐induced halide segregation in wide‐bandgap (WBG) perovskite leads to poor stability and limits its application in high‐efficiency tandem solar cells. Here, a simple solution strategy to achieve photostable WBG perovskite solar cells (PSCs) with bandgap of ≈1.67 eV by ionic coupling potassium sorbate with defects at the buried perovskite interface is reported. Moreover, the ionic coupled potassium sorbate (ICPS) enables to control the formation of N‐methyl formamidinium ions that can selectively passivate the perovskite defects at grain boundaries. As a result, the photo‐induced halide segregation in the target perovskite films is frozen under intense light. The target single‐junction WBG PSC achieves a record efficiency of 22.00% with an open‐circuit voltage (VOC) of 1.272 V and photostability of less than 2% decay over 2000 h of operation. Perovskite/Silicon tandem solar cells are also fabricated that achieve an efficiency of 30.72% (certified 30.09% @1.087 cm2), which is the highest efficiency reported to date with a tunneling oxide passivating contact (TOPCon) c‐Si substrate. The encapsulated tandem device can maintain 97% of its initial efficiency after 1000 h of operation.

Targeted Passivation of Perovskite Defects Using Multifunctional 2D Composite Nanostructures to Reduce Recombination Losses in Photovoltaic Cells

Defect‐induced recombination dynamics remain an essential factor hindering the efficiency and stability of perovskite solar cells (PSCs). Herein, an upgraded solvent posttreatment strategy is proposed to simultaneously improve the quality and related electronic properties of absorbers by introducing the black phosphorus–graphene oxide (BP–GO) composites with a unique microscopic heterojunction stacking structure, high charge mobility, tunable bandgap, and excellent surface chemical properties into the grain boundaries and surface of the perovskite. The BP–GO composites block the layer‐to‐layer diffusion of active ions while directionally passivating uncoordinated defects in the perovskite, thereby accelerating the carrier extraction/transfer at the perovskite interface, ultimately significantly reducing the nonradiative recombination and interfacial charge recombination losses of the devices. The BP–GO composites improve Oswald ripening, guaranteeing the formation of high‐crystallinity and large‐grain perovskites, thereby significantly enhancing the lattice stability, interface quality, and light‐harvesting capacity of the absorbers. Benefiting from the synergistic action of the unique lattice structure of BP–GO, excellent passivation/isolation effect, and enhanced charge dynamics, the photovoltaic output performance of the BP–GO‐modified PSCs is significantly higher than that of conventional n–i–p planar PSCs, and the corresponding unencapsulated device exhibits good stability. This work provides theoretical and technical guarantees for achieving more efficient and stable planar PSCs.

Facile synthesis of surface oxygen vacancy and Ti3+ defects in SrTiO3 perovskite coupled g-C3N4 decorated with Au ternary nanocomposites for enhancing electrocatalytic activity from acidic and natural seawater conditions

The development of efficient electrocatalysts became vital to resolving the ongoing clean energy crises and environmental issues, wherein high-performance catalysts for the improved electrocatalytic hydrogen evolution reaction (EHER) are demanded. To meet this goal, an advanced and green ultrasonic-assisted pulsed laser ablation in liquid technique was used to prepare surface oxygen vacancy and Ti3+ defects in perovskite-based ternary nanocomposites (PTNCs) decorated with Au@SrTiO3/g-C3N4. An effective cathode was designed using Au@SrTiO3/g–C3N4–decorated PTNCs for EHER that operated in an acidic media of 0.5 M H2SO4. The optimized Au@SrTiO3/g-C3N4 PTNCs revealed an improved EHER at a very low over-potential of 0.082 V at a cathodic current density (J) of −10 mA/cm2, high double-layer capacitance (679.8 μF/cm2), large electrochemical surface area (19.4 cm2), high mass activity (198.35 A/g), high specific activity (2.91 mA/cm2), high surface charge density (0.0404 C/cm2), high catalytic active sites (4.19 × 10−7 mol/cm2), and exceptional long-term stability at 50 h, respectively. The Tafel slope of 45.36 mV/dec confirmed the presence of the Volmer-Heyrovsky mechanism to explain the enhanced EHER cycle of the prepared PTNCs. The improved electrocatalytic EHER performance was attributed to the induced synergistic strong metal-support interaction (SMSI) effect of the surface oxygen vacancy and Ti3+ defects in PTNCs that increased electrochemical surface area, high exposure of abundant active sites, improved intrinsic kinetics, and fast charge transport, respectively. Moreover, Au@SrTiO3/g–C3N4–decorated PTNCs exhibit excellent natural seawater electrolysis in terms of EHER at a low over-potential of 0.300 V at a J = −10 mA/cm2 and long-term stability at 10 h, respectively. It is demonstrated that the proposed novel surface oxygen vacancy and Ti3+ defects in Au@SrTiO3/g-C3N4 PTNCs are effective electrocatalysts can be beneficial for producing hydrogen from green technologies in future energy applications via interface engineering.

Novel cathode buffer layer enabling over 21.6%/20.9% efficiency in wide bandgap/inorganic perovskite solar cells

Different types of hybrid organic/inorganic halide perovskite solar cells (PSCs) have attracted extensive research attention and showed extremely considerable practical application potential in current energy field, for instance, wide bandgap (WBG) PSCs are widely used in fabricating high-efficiency tandem devices, while inorganic perovskite solar cells (IPSCs) had been sought after by researchers due to its excellent thermal stability. However, either WBG PSCs or IPSCs were severely influenced by the carrier extraction and transport between the electron transfer layer and anode/cathode. On this basis, an in-situ oxygen plasma treated Ti doped ZnO film named TZO (O) was used as cathode buffer layer to regulate the energy-level alignment between the SnO2 layer and ITO electrode, optimize the crystal quality of perovskite and passivate perovskite defects through providing superior SnO2 film. It is found that the more suitable energy levels for the interlamination availably polished up carrier transport effect to a great extent, which could be seen in steady-state and time-resolved photoluminescence spectra, in addition to this, the perovskite film covered on TZO (O)/ SnO2 demonstrated larger perovskite crystals and less surface defects. As a consequence, the power conversion efficiency (PCE) of the optimized device with a bandgap of ≈ 1.66 eV up to 21.62%, and the efficiency of CsPbI2.85Br0.15 IPSCs is enhanced from 19.21% to 20.92%. Moreover, the unencapsulated TZO (O)-treated wide bandgap PSCs shows enhanced stability, retaining 89.47% of its initial efficiency after 1000 h in a N2 filled environment, while the unencapsulated IPSCs-based TZO (O) still remains 83.77% of its initial efficiency under continuous illumination in air for 325 h. This work exhibited that the buffer layer TZO (O) is a promising interfacial modification material for both n-i-p type wide bandgap PSCs and IPSCs.

A short overview of the lead iodide residue impact and regulation strategies in perovskite solar cells

Lead iodide (PbI2) is a vital raw material for preparing perovskite solar cells (PSCs), and it not only takes part in forming the light absorption layer but also remains in the grain boundary as a passivator. In other words, the PbI2 content in the precursor and as formed film will affect the efficiency and stability of the PSCs. With moderate residual PbI2, it passivates the bulk/surface defects of perovskite, reduces the interfacial recombination, promotes the perovskite stability, minimizes the device hysteresis, and so on. Deficient PbI2 residue will reduce the interfacial passivation effect and device performance. In addition to facilitating the non-radiative recombination, over PbI2 residue can also lead to electronic insulation in the grain boundary and deteriorate the device performance. However, the impact and regulation of PbI2 residue on the device performance and stability is still not fully understood. Herein, a comprehensive and detailed review is presented by discussing the PbI2 residue impact and its regulation strategies (i.e., elimination, facilitation and conversion of the residue PbI2) to manipulate the PbI2 content, distribution and forms. Finally, we also show future outlooks in this field, with an aim to help further the progression of high-efficiency and stable PSCs.

Buried interface management via bifunctional NH4BF4 towards efficient CsPbI2Br solar cells with a Voc over 1.4 V

CsPbI2Br perovskite solar cells (PSCs) have drawn tremendous attention due to their suitable bandgap, excellent photothermal stability, and great potential as an ideal candidate for top cells in tandem solar cells. However, the abundant defects at the buried interface and perovskite layer induce severe charge recombination, resulting in the open-circuit voltage (Voc) output and stability much lower than anticipated. Herein, a novel buried interface management strategy is developed to regulate interfacial carrier dynamics and CsPbI2Br defects by introducing ammonium tetrafluoroborate (NH4BF4), thereby resulting in both high CsPbI2Br crystallization and minimized interfacial energy losses. Specifically, NH4+ ions could preferentially heal hydroxyl groups on the SnO2 surface and balance energy level alignment between SnO2 and CsPbI2Br, enhancing charge transport efficiency, while BF4− anions as a quasi-halogen regulate crystal growth of CsPbI2Br, thus reducing perovskite defects. Additionally, it is proved that eliminating hydroxyl groups at the buried interface enhances the iodide migration activation energy of CsPbI2Br for strengthening the phase stability. As a result, the optimized CsPbI2Br PSCs realize a remarkable efficiency of 17.09% and an ultrahigh Voc output of 1.43 V, which is one of the highest values for CsPbI2Br PSCs.

Side chain modulated carbazole-based bifunctional hole-shuttle interlayer simultaneously improves interfacial energy level alignment and defect passivation in high-efficiency perovskite solar cells

Perovskite solar cells have reached a power conversion efficiency over 26.1 %, and the interface engineering between perovskite and hole transport layer (HTL) is crucial for achieving high performance. There exists a noticeable research gap when it comes to designing an interlayer layer that can both hold defect passivation and hole transportability. To bridge this gap, we have designed and synthesized two functional molecules with carbazole cores and side chain modifications, namely CVE-Br and CVE-DPA. Beyond the suitable energy levels of the carbazole group, CVE-Br can intercalate into perovskite lattice, create a low-dimensional perovskite, and further minimize defects. Instead of forming low dimensional structure, CVE-DPA molecule wraps around the perovskite. That makes it passivate perovskite defects and facilitate hole transport without the limitation of carrier transportation. As a result, the power conversion efficiency of perovskite solar cells with CVE-DPA can achieve 22.05 %. The hydrophobicity of CVE-DPA confers the corresponding devices to retain 87 % of the initial efficiency after 1000 h.

Crystallization Enhancement and Ionic Defect Passivation in Wide‐Bandgap Perovskite for Efficient and Stable All‐Perovskite Tandem Solar Cells

AbstractBy integrating wide‐bandgap (WBG) and narrow‐bandgap perovskites, monolithic all‐perovskite tandem solar cells have garnered significant attention as a prospective strategy for surpassing the efficiency limits of single‐junction cells. However, the WBG subcells, which significantly impact the performance and operational stability of all‐perovskite tandem solar cells, face notable challenges associated with pronounced nonradiative recombination losses and limited film photostability. Here, an efficient method is reported by adding potassium hypophosphite into the perovskite precursor solution to simultaneously regulate crystallization and passivate ionic defects in WBG perovskites. This approach results in high‐quality perovskite films and significantly improves the performance and photostability of WBG perovskite solar cells. The single‐junction devices with a 1.79 eV bandgap achieve a champion power conversion efficiency (PCE) of 20.06% with an open‐circuit voltage of 1.32 V. The devices retain ≈96% of their initial PCE following 913 h of continuous AM 1.5 G illumination. With these WBG perovskite subcells, monolithic all‐perovskite tandem solar cells are fabricated with an efficiency of 26.08%.

Synergistic Modification for Efficient Perovskite Solar Cells with Small Voltage Loss.

The power conversion efficiency (PCE) of perovskite solar cells has improved quickly in the past few years, but the PCE is still much lower than the theoretical limit. The relatively high energy loss (Eloss) is one of the critical factors limiting the PCE. To resolve the above issues, a synergistic modification strategy was used herein to minimize Eloss. RbCl and potassium polyacrylate (K-PAM) were used to modify the SnO2 layer. Additionally, Pb(Ac)2 was introduced into PbI2 to further improve the film quality. The synergistic modification strategy reduced the defects in SnO2 and perovskite and improved the energy-level alignment, enabling significantly reduced Eloss and enhanced photovoltaic performance. The best PCE of 24.07% was achieved, which was much higher than that of the control device (20.86%). The Eloss was only 0.349 eV for the target device. Good stability was achieved for the cells made using modified SnO2 and perovskite layers.

Donor-π-Acceptor Porphyrin-Assisted Bifunctional Defect Passivation for Enhanced Temporal Domain-/Wavelength-Dependent Nonlinear Absorption Properties in Perovskite Films.

Perovskite layer defects are a primary inhibiting factor for their optical nonlinearity, which restricts their use in nonlinear photonics devices. Nevertheless, due to the variety of defect types, the passivation and repair of these defects remain challenging. Herein, a novel bifunctional passivation strategy was proposed, and the porphyrin with a donor-π-acceptor structure was designed to bifunctionally repair perovskite defects by linking different types of functional groups via acetylenic π-conjugated linkage bridges on both sides, thus improving the nonlinear optical (NLO) absorption properties of porphyrin-perovskite hybrid materials. Research results indicate that the amino and carboxyl groups of porphyrins endow the ability to bifunctionally passivate charged defects via effective coordination interactions. The nonlinear absorption properties of all porphyrin-passivated MAPbI3 films were remarkably enhanced compared to that of the MAPbI3 film across multiple wavelengths and temporal domains. Particularly, the Por3-passivated perovskite film (MAPbI3/Por3) exhibited optimized strongest NLO performance, including reverse saturable absorption (RSA) under 800 nm femtosecond (fs) and 1064 nm nanosecond (ns) laser irradiations, as well as saturable absorption (SA) with 515 and 532 nm ns laser excitations. The value of the NLO absorption coefficient (β = 266.23 cm GW-1) is 1 order of magnitude higher than that of the pristine perovskite film (β = 12.93 cm GW-1), also outperforming other porphyrin-passivated perovskite films and some reported materials. The bifunctional passivation mechanism of porphyrin not only intensifies the perovskite's photoinduced ground-state dipole moment in the two-photon absorption (TPA) process and the free carrier absorption ability to deepen the RSA properties under 800 nm fs and 1064 nm ns lasers, respectively, but also enables the improvement of SA responses under 515 nm fs and 532 nm ns lasers by expediting the Pauli blocking effect of perovskite. Our study offers a viable paradigm, which aims at exploiting high-performance NLO perovskite materials across wide spectral regions and time scales.

Side‐Group‐Mediated Small Molecular Interlayer to Achieve Superior Passivation Strength and Enhanced Carrier Dynamics for Efficient and Stable Perovskite Solar Cells

AbstractConsidering the high surface defects of polycrystalline perovskite, chemical passivation is effective in reducing defects‐associated carrier losses. However, challenges remain in promoting passivation effects without compromising the carrier‐extraction yield at the perovskite interfaces. In this work, interlayer molecules functionalized with different side groups are rationally designed to investigate the correlation between defect‐passivation strength and interfacial carrier dynamics. It is revealed that Cl‐grafted molecules impose destructive effects on the perovskite structure due to its lower electronegativity and mismatched spatial configuration. The introduction of cyanide (CN) as a side group in molecules also leads to perovskite deformation and unfavorable hole collection. After the molecular optimization, the incorporation of carbonyl (C═O) as the side group (TPA─O) simultaneously promotes the carrier‐collection yield as well as sufficient defect passivation. As a consequence, the devices based on TPA─O yield a champion PCE of 23.25%, along with remarkable stability by remaining above 88.5% of initial performance after 2544 h storage in the air. Furthermore, this interlayer based on TAP─O enables flexible devices to achieve a high efficiency of 21.81% and promising mechanical stability. This work paves the way for further improving the performance of perovskite solar cells.

Enhancing perovskite solar cell performance through dynamic hydrogen-mediated polarization of nitrogen and sulfur in phthalocyanine

Perovskite defect passivation has been researched extensively as an essential technique to improve the efficiency and stability of perovskite solar cells (PSCs) and thus drive their future commercialization. Three phthalocyanines named NP-SC6-ZnPc, NP-SC6-CuPc, and NP-SC6-H2Pc were synthesized and use for PSCs passivation. Theoretical calculations and experimental verifications confirmed that NP-SC6-H2Pc had the best passivation effect on perovskites. The phthalocyanine ring’s central hydrogen atoms are transferred dynamically from NP-SC6-H2Pc and interact with the formamidinium lead iodide (FAPbI3) perovskite through nitrogen-hydrogen bonding, resulting in α-FAPbI3 perovskite formation and increasing the sulfur/nitrogen (S/N) passivation capability. FAPbI3-based PSCs treated with NP-SC6-H2Pc demonstrated the highest power conversion efficiency (PCE) of 24.03 % (certified PCE of 23.78 %) with excellent stability. This significant finding represents the first observation of dynamic transfer of the hydrogen atoms in phthalocyanine and provides a thorough investigation of the perovskite passivation mechanism.

Defect evolution of iodine vacancy and related strain modulation in all-inorganic halide perovskites

Vacancy related defects play a crucial role in optoelectronic properties and carrier transport for photovoltaic materials, especially for its structural evolution becoming non-radiative defects induced by strain. Thus far, the evolution phenomena of vacancy defects in halide perovskite triggered by energy or strain have not been systematically investigated. Herein, we study the change in defect levels occurred in different inorganic perovskite systems and the situation caused by strain in varied strength based on density functional theory calculations. We discover that VI deep levels are easily transformed from shallow levels due to the formation of Pb–Pb dimers and octahedral distortion in all-inorganic perovskites, especially in CsPbI3. Moreover, strain can be quantitatively applied to control the suppression or enhancement of the formation of dimer in CsBI3 (B = Pb/Ge) perovskites. Eventually, our calculation results unravel that the defect physics of VI defect and the formation mechanism of non-radiative center in all inorganic perovskites, which depends on the strain strength and the accompanying octahedral distortion. The strain modulation and its quantitation effect on defect evolution of dominant vacancy map a pioneering route toward fabricating high performance inorganic photovoltaics.

Pyridine group incorporated mixed electron transporting layers for high-performance perovskite light-emitting diodes

The unsaturated Pb2+ ions, located at the perovskite/charge transport layer (CTL) interfaces, are one of the main trap centers that result in non-radiative recombination of perovskite light-emitting diodes (PeLEDs), thus compromising device efficiency. Therefore, interface engineering and modulation are of significance in passivating the surface defects of the perovskite film as well as modifying the perovskite/CTL interface properties. In this work, a high-mobility pyridine-based electron transport material, 1,3,5-tri(m-pyrid-3-yl-phenyl) benzene (TmPyPB), is co-evaporated with 2,2',2"-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi) to form efficient electron-transport layers (ETLs) for PeLEDs. The interaction of the pyridine group of TmPyPB with the uncoordinated Pb2+ ions can effectively passivate the perovskite defects. Furthermore, the mixed ETL can also enhance electron mobility by tuning the mixing ratios between the TmPyPB and TPBi, thus boosting the device efficiency. As a result, PeLEDs with enhanced electron mobility and reduced defects are prepared, in which the device exhibits a maximum current density (CE) of 74 cd/A and an external quantum efficiency (EQE) of 25.4%. This EQE is nearly two fold higher than that of the pure TPBi-based PeLEDs.

Bilayer phosphine oxide modification toward efficient and large-area pure-blue perovskite quantum dot light-emitting diodes

Blue emissive halide perovskite light-emitting diodes (LEDs) are gaining increasing attention. Reducing defects in halide perovskites to improve the performance of the resulting LEDs is a main research direction, but there are limited passivation methods for achieving efficient and spectrally-stable pure-blue LEDs based on mixed-halide perovskites. In this work, double modification layers containing phosphine oxides, i.e., diphenyl[4-(triphenylsilyl)phenyl]phosphine oxide (TSPO1) and 2,7-bis(diphenylphosphoryl)-9,9′-spirobifluorene (SPPO13), are developed to passivate mixed-halide perovskite quantum dot (QD) films. The comprehensive spectroscopic and structural characterization results indicate the presence of strong interactions between TSPO1/SPPO13 and the QDs. Besides, the combination of the bilayer exhibits a synergistic hole-blocking effect, improving the charge balance of the LEDs. LEDs based on the QD/TSPO1/SPPO13 films deliver stable electroluminesence at 469 nm and present a maximum external quantum efficiency (EQE) and luminance of 4.87% and 560 cd m−2, respectively. Benefiting from the uniform QD/TSPO1/SPPO13 film over a large area, LEDs with an area of 64 mm2 show a maximum EQE of 3.91%, which represents the first efficient large-area mixed-halide perovskite LED with stable pure-blue emission. This work provides a method to improve the perovskite QDs-based film quality and optoelectronic properties, and is a step toward the fabrication of highly-efficient large-area blue perovskite LEDs.

Two birds with one stone: dopant-free squaraine hole-transporting material for perovskite solar cell

Developing alternative dopant-free hole-transporting materials (HTM) with a passivation effect and high hole mobility is significant for enhancing the power conversion efficiency (PCE) and stability of the perovskite solar cells (PSCs) with a simplified process. In this work, we report a squaraine HTM 3,4-bis(4'-(bis(4-methoxyphenyl)amino)-[1,1′-biphenyl]-4-yl)cyclobut-3-ene-1,2-dione (D12) with a resonance central structure shuttling between electrically neutral dione and charge-separated inner salts. The donor-acceptor-donor type molecule D12 exhibits an extremely strong capacity not only for hole exaction and mobility, but also for the passivation of perovskite defects. This results in a high PCE of 22.32% for D12-based PSCs. After 30 days of aging at a high relative humidity of 65% at 30 °C, it remains 90% of its initial PCE. This work offers a strategy of designing dopant-free small-molecule HTM and enhancing the stability and PCE of PSCs.

5‐Chloro‐2‐Hydroxypyridine Derivatives with Push‐Pull Electron Structure Enable Durable and Efficient Perovskite Solar Cells

AbstractTargeted passivation of defects in perovskite is the primary consideration in the design of additives containing functional groups. However, the precise modulation of electron structure in functional groups and the structure‐activity relationship between electronic configuration and performance of perovskite solar cells (PSCs) still need to be explored. In this study, 5‐chloro‐2‐hydroxypyridine derivatives with –NH2 (HNCLP) and –F (HFCLP) end groups are selected to realize the push‐pull electronic structure configuration. Density functional theory demonstrates that, compared with HFCLP, HNCLP with the electron‐donating terminal of –NH2 has a long dipole moment and immobilize the interstitial I3−, and the N side of pyridine with high‐density electron cloud enables strong passivation with undercoordinated Pb2+ ions. The experimental results confirm that HNCLP with optimized electronic configuration emerges strong passivation ability, greatly suppresses the nonradiative recombination of perovskite absorber, and remarkably improves the film crystal quality along with the extraction and transfer process of photogenerated carriers. The HNCLP‐contained PSC exhibits a remarkable efficiency of 24.47%, and HNCLP helps to enhance the moisture‐proof of perovskite film and device storage stability.

Thiocyanate-Stabilized Pseudo-cubic Perovskite CH(NH2)2PbI3 from Coincident Columnar Defect Lattices.

α-FAPbI3 (FA+ = CH(NH2)2+) with a cubic perovskite structure is promising for photophysical applications. However, α-FAPbI3 is metastable at room temperature, and it transforms to the δ-phase at a certain period of time at room temperature. Herein, we report a thiocyanate-stabilized pseudo-cubic perovskite FAPbI3 with ordered columnar defects (α'-phase). This compound has a √5ap × √5ap × ap tetragonal unit cell (ap: cell parameter of primitive perovskite cell) with a band gap of 1.91 eV. It is stable at room temperature in a dry atmosphere. Furthermore, the presence of the α'-phase in a mixed sample with the δ-phase drastically reduces the δ-to-α transition temperature measured on heating, suggesting the reduction of the nucleation energy of the α-phase or thermodynamic stabilization of the α-phase through epitaxy. The defect-ordered pattern in the α'-phase forms a coincidence-site lattice at the twinned boundary of the single crystals, thus hinting at an epitaxy- or strain-based mechanism of α-phase formation and/or stabilization. In this study, we developed a new strategy to control defects in halide perovskites and provided new insight into the stabilization of α-FAPbI3 by pseudo-halide and grain boundary engineering.

Highly Efficient Hybrid Perovskite/Organic Tandem White Light Emitting‐Diodes with External Quantum Efficiency Exceeding 20%

AbstractPerovskite light‐emitting diodes (PeLEDs) have shown great potential for low‐cost display and lighting technologies, and all‐inorganic blue PeLEDs are recognized as a promising substitute for blue fluorescent/phosphorescent organic light‐emitting diodes (OLEDs) owing to their superior color purity and great stability potential. However, confined by the solution fabrication process, depositing multi‐layered white PeLEDs remains a challenge. Here, a newly designed hybrid perovskite/organic tandem white LED (POTWLED), integrated with a bottom blue PeLED unit and a top orange/(orange + red) OLED unit, to prevent damage to the underlying perovskite layer caused by the deposition of the top emitting layers, is reported. To optimize the performance of POTWLEDs, a conductive passivator of 2,8‐bis(diphenylphosphoryl)dibenzo[b,d] thiophene, with a strong surface binding group of P═O, is introduced to passivate perovskite defects, which promotes a maximum external quantum efficiency (EQE) of 17.3% for blue PeLEDs with an emission peak at 488 nm. As a result, based on the optimized blue PeLED units, a maximum EQE of 23.9% with a low color temperature of 2522 K is obtained for POTWLEDs, which is the highest efficiency for perovskite‐based WLEDs, illustrating the great potential of the hybrid tandem device in fabricating high‐performance perovskite‐based WLEDs.

Bifunctional trifluorophenylacetic acid additive for stable and highly efficient flexible perovskite solar cell

AbstractThe defects within perovskite films are the fatal roadblock limiting the performance of perovskite solar cells (PSCs). Herein, we develop a patching strategy to obtain high‐quality perovskite film using bifunctional trifluorophenylacetic acid (TFPA). Theoretical calculation and experiments reveal that the –COOH groups in TFPA effectively passivate the deep‐energy‐level defects of perovskite by combining with Pb clusters on the perovskite grain surfaces to enhance the efficiency of PSCs, and hydrophobic benzene groups containing fluorine in TFPA are exposed to improve the stability of PSCs. The power conversion efficiency (PCE) of PSCs with TFPA is enhanced from 22.95% to 24.56%. Most importantly, we successfully fabricated flexible PSCs using TFPA with the high PCE of 22.65%. The devices with TFPA maintain 93.22% of the initial efficiency MPP under continuous irradiation for 10.5 h, while the devices without TFPA only retain 82.22% of the initial efficiency under the same conditions for just 5 h. Meanwhile, the unsealed devices with TFPA hold 93.59% of the initial efficiency when stored in air for 3912 h.image