JIALINGBO

In order to investigate the nature and strength of noncovalent interactions at the fullerene surface, molecular torsion balances consisting of C60 and organic moieties connected through a biphenyl linkage were designed, synthesized, and characterized. NMR spectroscopy combined with computational studies showed that the unimolecular system remains in equilibrium between well‐defined folded and unfolded conformers owing to restricted rotation around the biphenyl C–C bond. The measured energy differences between the two conformers depend on the substituents and can, in turn, be ascribed to the differences in the intramolecular noncovalent interactions between the organic moieties and the fullerene surface. Notably, the results showed that fullerenes favor interacting with the p‐faces of benzenes bearing electron‐donating substituents. The correlation between the folding free energies and the corresponding Hammett constants of the substituents in the arene‐containing torsion balances is reflective of the contributions of the electrostatic interactions and dispersion force to the face‐to‐face arene–fullerene interactions.

Passivation Agents

In article number 2000082, Fei Zhang, Kai Zhu, and co‐workers design a more efficient and stable perovskite solar cell by partially replacing phenylethylammonium (PEA⁺) with pentauorophenethylammonium (F5PEA⁺) as the 2D perovskite passivation agent by forming a strong noncovalent interaction between the two bulky cations, which enhances charge transport, and presents the highest performance for reported wide‐bandgap perovskite solar cells.

Perovskite Solar Cells

In article number 2000093, Ming‐Chung Wu, Kun‐Mu Lee, and co‐workers use polyethylene glycol (PEG) as an additive for the perovskite active layer in lead‐reduced perovskite solar cells. The PEG can effectively control the surface morphology of the perovskite film and improve the charge carrier transport. For 10% lead‐reduced perovskite solar cells, a champion power conversion effi ciency of 16.1% is obtained without signifi cant hysteresis.

The surface and bulk defects of perovskite films are simultaneously passivated through the treatment of CsBr/methanol solution, in which the methanol helps CsBr penetrate the depth of the perovskite and reconstruct high‐quality films. This strategy can effectively improve the photovoltaic performance and operational stability of the resultant devices.

It is challenging to passivate defects that are buried in the depth of perovskite films; most of the reported passivation methods cannot reach the deep defects. Herein, methanol is adopted as a dual‐functional reagent to not only act as a solvent but also help the dissolved ions penetrate the depth of perovskite films. By treating the as‐prepared perovskite films with CsBr/methanol solution, Br⁻ ions can react with the undercoordinated Pb²⁺, and Cs⁺ ions can fill in the cation vacancies. This strategy enables surface and bulk defects passivation to be achieved simultaneously. The nonradiative recombination of the double‐passivated devices is significantly suppressed and the migration of charged defects is remarkably hindered. As a result, an improved power conversion efficiency of 19.5% and an open‐circuit voltage of 1.183 V is achieved. Moreover, the passivated device can retain ≈80% of the initial efficiency after working for 500 h at maximum power point under 1‐sun illumination, whereas the pristine device reaches 80% of the initial efficiency after only 90 h. This work demonstrates that surface and bulk defects passivation is critical to improve the efficiency and long‐term operational stability of the perovskite solar cells.

Dramatically boosted device performance is observed from perovskite photovoltaics by magnetic field‐aligned CH₃NH₃PbI₃:Fe₃O₄ composite thin films, which possesses superior film morphology, boosted and balanced charge carrier mobility, suppressed trap density and charge carrier recombination, and promoted charge carrier extraction time.

Abstract

Perovskite photovoltaics have drawn great attention in both academic and industrial sectors in the past decade. To date, impressive device performance has been achieved in state‐of‐the‐art device architectures through morphological manipulation and generic interface engineering. In this study, enhanced device performance of perovskite photovoltaics by magnetic field‐aligned CH₃NH₃PbI₃‐mixed Fe₃O₄ magnetic nanoparticles (CH₃NH₃PbI₃:Fe₃O₄) composite thin films is reported. It is found that magnetic field‐aligned CH₃NH₃PbI₃:Fe₃O₄ composite thin films possess superior film morphology, boosted and balanced charge carrier mobility, and suppressed trap density. Moreover, perovskite photovoltaics by magnetic field‐aligned CH₃NH₃PbI₃:Fe₃O₄ composite thin films exhibit suppressed charge carrier recombination and shorter charge carrier extraction time. As a result, perovskite solar cells by magnetic field‐aligned CH₃NH₃PbI₃:Fe₃O₄ composite thin films exhibit 20.23% power conversion efficiency with significantly reduced photocurrent hysteresis. Moreover, perovskite photodetectors by magnetic field‐aligned CH₃NH₃PbI₃:Fe₃O₄ composite thin films exhibit a photoresponsivity of 858 mA W⁻¹, a photodetectivity over 10¹³ Jones (1 Jones = 1 cm Hz^1/2 W⁻¹) and a linear dynamic range over 160 dB at room temperature. All these device performance parameters are significantly better than those by pristine CH₃NH₃PbI₃ thin film. Thus, these studies provide a facile way to boost device performance of perovskite photovoltaics.

An effective strategy is demostrated to create a double barrier that not only blocks the invasion of the moisture but also takes advantage of the permeated moisture to increase the moisture durability of perovskite films, which results in an n–i–p perovskite solar cell with moisture stability over 115 days in a relative humidity of 70% and a champion efficiency up to 21.34%.

Abstract

The rapid growth in the device efficiency of perovskite solar cells (PSCs) has raised great demands for tackling their long‐term stability upon external environmental stimuli that restricts the commercialization of PSCs, in which the instability upon exposure to moisture has been one of the major obstacles. Herein, an effective way of building up double barriers for moisture degradation of the perovskite films is demonstrated by modifying them with rationally selected hydrolyzable hydrophobic molecules (1H,1H,2H,2H‐perfluorooctyl trichlorosilane, PFTS). The layer of oligomer derived from the hydrolyzed PFTS at the surface that increases the hydrophobicity of perovskite film could serve as an efficient wall preventing the moisture invasion. The long‐term exposure of the film upon moisture allows for the formation of a secondary wall that employs the hydrolyzation of PFTS at grain boundaries, favoring defects passivation to further improve the humidity stability. Such gradual hydrolyzation is encouragingly helpful for the enhancement of the open‐circuit voltage of the PSCs from the original 1.136 up to 1.205 V. The PSCs constructed with the double barriers demonstrate excellent stability upon moisture and improved thermal and light stabilities, as well as a champion power conversion efficiency up to 21.34%.

A multi‐technique in situ structural and optoelectronic characterization on planar perovskite solar cells reveals perovskite amorphization and phase segregation as the crucial degradation mechanisms due to ion migration on a daily timescale. The degradation has a severe negative impact on the charge collection, which reduces the photocurrent and the power conversion efficiency. The mechanism is partially reversible after rest in the dark.

Abstract

The operation of halide perovskite optoelectronic devices, including solar cells and LEDs, is strongly influenced by the mobility of ions comprising the crystal structure. This peculiarity is particularly true when considering the long‐term stability of devices. A detailed understanding of the ion migration‐driven degradation pathways is critical to design effective stabilization strategies. Nonetheless, despite substantial research in this first decade of perovskite photovoltaics, the long‐term effects of ion migration remain elusive due to the complex chemistry of lead halide perovskites. By linking materials chemistry to device optoelectronics, this study highlights that electrical bias‐induced perovskite amorphization and phase segregation is a crucial degradation mechanism in planar mixed halide perovskite solar cells. Depending on the biasing potential and the injected charge, halide segregation occurs, forming crystalline iodide‐rich domains, which govern light emission and participate in light absorption and photocurrent generation. Additionally, the loss of crystallinity limits charge collection efficiency and eventually degrades the device performance.

Formamidinium methylammonium (FAMA)‐perovskite‐Cu:NiO and Al₂O₃/Cu:NiO composites are developed for highly stable and efficient perovskite solar cells. The composites not only improve the perovskite film quality but also suppress charge recombination with substantial reduction of trap density. The composites based devices yielded power conversion efficiency of 20.7% with fill factor of 80.5%. More importantly, unencapsulated cells showed significant enhancement of air‐stability, thermal‐ and photo‐stability with retaining 97% of PCE over 240 days under ambient conditions.

Abstract

To solve critical issues related to device stability and performance of perovskite solar cells (PSCs), FA_0.026MA_0.974PbI_{3− y} Cl _y ‐Cu:NiO (formamidinium methylammonium (FAMA)‐perovskite‐Cu:NiO) and Al₂O₃/Cu:NiO composites are developed and utilized for fabrication of highly stable and efficient PSCs through fully‐ambient‐air processes. The FAMA‐perovskite‐Cu:NiO composite crystals prepared without using any antisolvents not only improve the perovskite film quality with large‐size crystals and less grain boundaries but also tailor optical and electronic properties and suppress charge recombination with reduction of trap density. A champion device based on the composites as light absorber and Al₂O₃/Cu:NiO interfacial layer between electron transport layer and active layer yields power conversion efficiency (PCE) of 20.67% with V _OC of 1.047 V, J _SC of 24.51 mA cm⁻², and fill factor of 80.54%. More importantly, such composite‐based PSCs without encapsulation show significant enhancement in long‐term air‐stability, thermal‐ and photostability with retaining 97% of PCE over 240 d under ambient conditions (25–30 °C, 45–55% humidity).

The Lewis base poly(ethylene glycol) (PEG) is introduced to assist the crystallization and growth of CsPbIBr₂ perovskite, yielding a pinhole‐free perovskite film with reduced defect states and favorable band energy level. Finally, the optimal device achieves a superior power conversion efficiency of 11.10% and great long‐term stability.

Abstract

Cesium lead mixed‐halide perovskite (CsPbIBr₂), as one of the all‐inorganic perovskites, has attracted great attention owing to its great ambient stability and suitable bandgap. Unfortunately, due to its low film coverage, high density of defects and unfavorable band energy level, the CsPbIBr₂ based solar cells suffer from low efficiency. In this work, the Lewis base poly(ethylene glycol) (PEG) is adopted as additive to modify the pure CsPbIBr₂. By optimizing the molecular weight and dosage of PEG, the resultant PEG:CsPbIBr₂ film possesses suppressed non‐radiative electron–hole recombination, a favorable energy band structure and a weaker sensitive to the moisture. As a result, the device based on the PEG:CsPbIBr₂ yields a champion power conversion efficiency (PCE) of 11.10%, with a open‐circuit voltage of 1.21 V, a short‐circuit current of 12.25 mA cm⁻², and a fill factor of 74.82%, which is 44.3% higher than its counterpart without PEG. Moreover, the PEG modified device shows excellent long‐term stability, retaining over 90% of the initial efficiency after 600 h storage in ambient condition without encapsulation. In comparison, the device without PEG shows an inferior stability with PCE sharply dropping to 0% within 50 h.

This review summarizes recent advances in the application of inorganic materials such as copper‐based compounds, with an emphasis on copper iodide and copper thiocyanate, transition metal chalcogenides, carbides, and nitrides as well as hybrid materials including copper compounds as hole and electron transport layers in organic and perovskite solar cells.

Abstract

As organic solar cells (OSCs) and perovskite solar cells (PVSCs) move closer to commercialization, further efforts toward optimizing both cell efficiency and stability are needed. As interfaces strongly affect device performance and degradation processes, interfacial engineering by employing various materials as hole transport layers (HTLs) and electron transport layers (ETLs) has been a very active field of research in OSCs and PVSCs. Among them, inorganic materials exhibit significant advantages in promoting device performance due to their excellent charge transporting properties and intrinsic thermal and chemical robustness. In this review, an extensive overview is provided of inorganic semiconductors such as copper‐based ones with emphasis on copper iodide and copper thiocyanate, transition metal chalcogenides, nitrides and carbides as well as hybrid materials based on these inorganic compounds that have been recently employed as HTLs and ETLs in OSCs and PVSCs. Following a short discussion of the main optoelectronic and physical properties that interfacial materials used as HTLs and ETLs should possess, the functionalities of the aforementioned materials as interfacial, charge transport, layers in OSCs and PVSCs are discussed in depth. It is concluded by providing guidelines for further developments that could significantly extend the implementation of these materials in solar cells.

An autonomously longitudinal scaffold constructed by the interspersion of in situ polymerized methyl methacrylate in PbI₂ is introduced to effectively eliminate the dependence of sequential deposition on mesoporous TiO₂, and is applied in planar perovskite solar cells, with excellent performance. Moreover, this scaffold's cross‐linking grains are capable of releasing mechanical stress, impeding ion migration, and water/oxygen permeation.

Abstract

Sequential deposition is certified as an effective technology to obtain high‐performance perovskite solar cells (PVSCs), which can be derivatized into large‐scale industrial production. However, dense lead iodide (PbI₂) causes incomplete reaction and unsatisfactory solution utilization of perovskite in planar PVSCs without mesoporous titanium dioxide as a support. Here, a novel autonomously longitudinal scaffold constructed by the interspersion of in situ self‐polymerized methyl methacrylate (sMMA) in PbI₂ is introduced to fabricate efficient PVSCs with excellent flexural endurance and environmental adaptability. By this strategy perovskite solution can be confined within an organic scaffold with vertical crystal growth promoted, effectively inhibiting exciton accumulation and recombination at grain boundaries. Additionally, sMMA cross‐linked perovskite network can release mechanical stress and occupy the main channels for ion migration and water/oxygen permeation to significantly improve operational stability, which opens up a new strategy for the commercial development of large‐area PVSCs in flexible electronics.

The efficiency and operational stability of MA‐free FA_0.95Cs_0.05PbI₃ perovskite solar cells can be simultaneously enhanced by the incorporation of the β‐guanidinopropionic acid (β‐GUA) molecule. The introduction of β‐GUA forms a 2D/3D hybrid perovskite phase, which effectively passivates the surface defects, resulting in an impressive power conversion efficiency of 22.2% with a substantial increase in V _oc (from 1.01 to 1.14 V).

Abstract

Almost all highly efficient perovskite solar cells (PVSCs) with power conversion efficiencies (PCEs) of greater than 22% currently contain the thermally unstable methylammonium (MA) molecule. MA‐free perovskites are an intrinsically more stable optoelectronic material for use in solar cells but compromise the performance of PVSCs with relatively large energy loss. Here, the open‐circuit voltage (V _oc) deficit is circumvented by the incorporation of β‐guanidinopropionic acid (β‐GUA) molecules into an MA‐free bulk perovskite, which facilitates the formation of quasi‐2D structure with face‐on orientation. The 2D/3D hybrid perovskites embed at the grain boundaries of the 3D bulk perovskites and are distributed through half the thickness of the film, which effectively passivates defects and minimizes energy loss of the PVSCs through reduced charge recombination rates and enhanced charge extraction efficiencies. A PCE of 22.2% (certified efficiency of 21.5%) is achieved and the operational stability of the MA‐free PVSCs is improved.

An environmentally stable acetamidinium (Aa⁺)‐incorporated MAPbI₃ film is successfully fabricated via hot casting in air. The large Aa⁺ immobilizes ions and improves crystal structure of MAPbI₃ through strong coordination bonds. The corresponding Aa–MAPbI₃ device shows 20.68% power conversion efficiency. Its 80% is maintained after 1300 h testing at 85 °C and 85 relative humidity (RH)%.

Ion migration in organometal halide perovskite solar cell (OHPSC) and crystal structure evolution of organometal halide perovskites (OHPVSKs) in air are considered as one of the critical factors for unstable performance and of the urgent issues for the reliability of OHPSCs. Herein, a novel cation of acetamidinium (Aa⁺) with stronger coordinated bond with I⁻ than methylammonium is induced into OHPVSK to stabilize its crystal structure. By incorporating Aa⁺ ions into OHPVSKs, the power conversion efficiency (PCE) of OHPSC without an encapsulation can maintain higher than 75% of its initial PCE after a 200 h humidity (60–80% relative humidity (RH) in air) or a 24 h thermal stress test (85 °C in dry N₂). The Aa–MAPbI₃ device exhibits an outstanding efficiency of 20.68%, and over 80% of initial PCE is maintained after a 1300 h damp heat as encapsulated. This novel cation can be easily incorporated into OHPVSK via a hot casting process in air with a high environmental tolerance as compared with that from the conventional coating process, which suffers from sophisticated crystallization steps and a strict processing atmosphere. It extends processing windows for OHPVSK fabrication and provides a promising path toward mass production and further commercialization.

One multifunctional molecule, 5‐amino‐2,4,6‐triiodoisophthalic acid (ATPA), is used as an interfacial layer between CsPbI₃ and TiO₂. The ATPA not only results in cascade energy‐level alignment, but also interacts strongly with the CsPbI₃ layer and effectively passivates the defects. Optimized devices based on the ATPA‐modified CsPbI₃ deliver a high efficiency of 18.12% with excellent stability.

A highly effective interface engineering approach uses a multifunctional molecule, 5‐amino‐2,4,6‐triiodoisophthalic acid (ATPA), to anchor on TiO₂ and CsPbI₃ simultaneously by reacting with dangling hydroxyl groups on TiO₂ surfaces and passivating the defects of CsPbI₃ films. In addition, the introduction of ATPA results in cascade energy‐level alignment between the perovskite and TiO₂ electron‐transporting layer (ETL) to improve the electron extraction property. Based on the ATPA‐modified TiO₂ substrates, optimized CsPbI₃ perovskite solar cells (PVSCs) deliver the highest power conversion efficiency (PCE) of over 18% with suppressed hysteresis. Moreover, the unencapsulated TiO₂/ATPA‐based devices exhibit much better long‐term stability and photostability than the only TiO₂‐based devices.

FAPbI₃‐based perovskite materials are of interest for photovoltaics in view of their close‐to‐ideal bandgap; however, FAPbI₃‐based materials suffer from notorious phase transition from the photoactive black phase (α‐FAPbI₃) to nonperovskite yellow phase (δ‐FAPbI₃) under ambient conditions. This study reveals that 1‐hexyl‐3‐methylimidazolium iodide ionic liquid incorporation stabilizes the α‐FAPbI₃ phase and exhibits a promising efficiency exceeding 20% with excellent long‐term operational and shelf‐stability.

Abstract

Formamidinium lead triiodide (FAPbI₃)‐based perovskite materials are of interest for photovoltaics in view of their close‐to‐ideal bandgap, allowing absorption of photons over a broad solar spectrum. However, FAPbI₃‐based materials suffer from a notorious phase transition from the photoactive black phase (α‐FAPbI₃) to nonperovskite yellow phase (δ‐FAPbI₃) under ambient conditions. This transition dramatically reduces light absorbtion, thus, degrading the photovoltaic performance and stability of ensuring solar cells. In this study, 1‐hexyl‐3‐methylimidazolium iodide (HMII) ionic liquid (IL) is employed as an additive for the first time in FAPbI₃ perovskite to overcome the above‐mentioned issues. HMII incorporation facilitates the grain coarsening of FAPbI₃ crystal owing to its high‐polarity and high‐boiling point, which yields liquid domains between neighboring grains to reduce the activation energy of the grain‐boundary migration. As a result, the FAPbI₃ active layer exhibits micron‐sized grains with substantially suppressed parasitic traps with an Urbach energy reduced by 2 meV. Hence, the resulting perovskite solar cell achieves an efficiency of 20.6% with notable increase in open circuit voltage (V _OC) of 80 mV compared with HMII‐free cells (17.1%). More importantly, the HMII‐doped FAPbI₃‐based cells show a striking enhancement in shelf‐stability under high humidity and thermal stress, retaining >80% of their initial efficiencies at 60 ± 10% relative humidity and ≈95% at 65 °C.

FAPbI₃‐based perovskite materials are of interest for photovoltaics in view of their close‐to‐ideal bandgap; however, FAPbI₃‐based materials suffer from notorious phase transition from the photoactive black phase (α‐FAPbI₃) to nonperovskite yellow phase (δ‐FAPbI₃) under ambient conditions. This study reveals that 1‐hexyl‐3‐methylimidazolium iodide ionic liquid incorporation stabilizes the α‐FAPbI₃ phase and exhibits a promising efficiency exceeding 20% with excellent long‐term operational and shelf‐stability.

Abstract

Formamidinium lead triiodide (FAPbI₃)‐based perovskite materials are of interest for photovoltaics in view of their close‐to‐ideal bandgap, allowing absorption of photons over a broad solar spectrum. However, FAPbI₃‐based materials suffer from a notorious phase transition from the photoactive black phase (α‐FAPbI₃) to nonperovskite yellow phase (δ‐FAPbI₃) under ambient conditions. This transition dramatically reduces light absorbtion, thus, degrading the photovoltaic performance and stability of ensuring solar cells. In this study, 1‐hexyl‐3‐methylimidazolium iodide (HMII) ionic liquid (IL) is employed as an additive for the first time in FAPbI₃ perovskite to overcome the above‐mentioned issues. HMII incorporation facilitates the grain coarsening of FAPbI₃ crystal owing to its high‐polarity and high‐boiling point, which yields liquid domains between neighboring grains to reduce the activation energy of the grain‐boundary migration. As a result, the FAPbI₃ active layer exhibits micron‐sized grains with substantially suppressed parasitic traps with an Urbach energy reduced by 2 meV. Hence, the resulting perovskite solar cell achieves an efficiency of 20.6% with notable increase in open circuit voltage (V _OC) of 80 mV compared with HMII‐free cells (17.1%). More importantly, the HMII‐doped FAPbI₃‐based cells show a striking enhancement in shelf‐stability under high humidity and thermal stress, retaining >80% of their initial efficiencies at 60 ± 10% relative humidity and ≈95% at 65 °C.

An effective strategy is demostrated to create a double barrier that not only blocks the invasion of the moisture but also takes advantage of the permeated moisture to increase the moisture durability of perovskite films, which results in an n–i–p perovskite solar cell with moisture stability over 115 days in a relative humidity of 70% and a champion efficiency up to 21.34%.

Abstract

The rapid growth in the device efficiency of perovskite solar cells (PSCs) has raised great demands for tackling their long‐term stability upon external environmental stimuli that restricts the commercialization of PSCs, in which the instability upon exposure to moisture has been one of the major obstacles. Herein, an effective way of building up double barriers for moisture degradation of the perovskite films is demonstrated by modifying them with rationally selected hydrolyzable hydrophobic molecules (1H,1H,2H,2H‐perfluorooctyl trichlorosilane, PFTS). The layer of oligomer derived from the hydrolyzed PFTS at the surface that increases the hydrophobicity of perovskite film could serve as an efficient wall preventing the moisture invasion. The long‐term exposure of the film upon moisture allows for the formation of a secondary wall that employs the hydrolyzation of PFTS at grain boundaries, favoring defects passivation to further improve the humidity stability. Such gradual hydrolyzation is encouragingly helpful for the enhancement of the open‐circuit voltage of the PSCs from the original 1.136 up to 1.205 V. The PSCs constructed with the double barriers demonstrate excellent stability upon moisture and improved thermal and light stabilities, as well as a champion power conversion efficiency up to 21.34%.

Lawful behavior : A wide range of monodisperse lead perovskite nanocrystals with different cation and anion compositions and varying sizes were synthesized and their biexciton Auger recombination lifetimes measured by ultrafast spectroscopy (see picture). Volume scaling laws for the Auger lifetime of the nanocrystals were determined, thus enabling facile estimation of Auger rates, which are key parameters for perovskite‐nanocrystal‐based devices.

Abstract

Lead halide perovskite nanocrystals (NCs) hold strong promise for a variety of light‐harvesting, emitting, and detecting applications, all of which, however, could be complicated by multicarrier Auger recombination. Therefore, complete documentation of the size‐ and composition‐dependent Auger recombination rates of these NCs is highly desirable, as it can guide system design in many applications. Herein we report the synthesis and Auger measurements of monodisperse APbX₃ (A=Cs and FA; X=Cl, Br, and I) NCs in an extensive size range (ca. 3–9 nm). The biexciton Auger lifetime of all the NCs scales linearly with the NC volume. The scaling coefficient is virtually independent of the cation but rather depends sensitively on the anion, and is 0.035, 0.085, and 0.142 ps nm⁻³ for Cl, Br, and I, respectively. In all of these nanocrystals the Auger recombination is much faster than in standard CdSe and PbSe NCs (ca. 1 ps nm⁻³).

Perovskite solar cells (PSCs) are a promising photovoltaic technology for stretchable applications. A self‐healing polyurethane (s‐PU) is applied as a scaffold in perovskite films where it enhances crystallinity and passivates the grain boundary. The stretchable PSCs with s‐PU have a stable efficiency of 19.15 %. The s‐PU releases mechanical stress and repairs cracks at the grain boundary. Devices cycled 1000 times at 20 % stretch regained 88 % of their original efficiency.

Abstract

Perovskite solar cells (PSCs) are a promising photovoltaic technology for stretchable applications because of their flexible, light‐weight, and low‐cost characteristics. However, the fragility of crystals and poor crystallinity of perovskite on stretchable substrates results in performance loss. In fact, grain boundary defects are the “Achilles’ heel” of optoelectronic and mechanical stability. We incorporate a self‐healing polyurethane (s‐PU) with dynamic oxime–carbamate bonds as a scaffold into the perovskite films, which simultaneously enhances crystallinity and passivates the grain boundary of the perovskite films. The stretchable PSCs with s‐PU deliver a stabilized efficiency of 19.15 % with negligible hysteresis, which is comparable to the performance on rigid substrates. The PSCs can maintain over 90 % of their initial efficiency after 3000 hours in air because of their self‐encapsulating structure. Importantly, the self‐healing function of the s‐PU scaffold was verified in situ. The s‐PU can release mechanical stress and repair cracks at the grain boundary on multiple levels. The devices recover 88 % of their original efficiency after 1000 cycles at 20 % stretch. We believe that this ingenious growth strategy for crystalline semiconductors will facilitate development of flexible and stretchable electronics.

The undercoordinated ionic defects at heterojunction interfaces remain challenges that limit the performances and stability of perovskite photoelectric devices. A self‐phase separated doping strategy is developed to link multilayer heterojunction interfaces including both the energy level and trap states, paving a novel route for nonequilibrium distributed dopants to solve the key challenge of interface defects.

Abstract

In perovskite solar cells (PSCs), the interfaces of the halide perovskite/electron transport layer (ETL) and ETL/metal oxide electrode (MOE) always attract and trap free carriers via the surface electrostatic force, altering quasi‐Fermi level (E _Fq) splitting of contact interfaces, and significantly limit the charge extraction efficiency and intrinsic stability of devices. Herein, a graded “bridge” is first reported to link the MOE and perovskite interfaces by self vertical phase separation doping (PSD), diminishing the side effect of notorious ionic defects via both reinforced interface E _bi and the vacancies filling. Experimental and theoretical results prove that the inhomogeneous distribution of CsF in the bulk or surface of PC₆₁BM would not only form metal–oxygen (M–O) dipole on MOE, reinforcing the interface E _bi, but also create a graded energy bridge to alleviate the disadvantage of band offset raised by the enhanced interface E _bi, which significantly avoid the carrier accumulation and recombination at defective interfaces. Employing PSD, the power conversion efficiency of the devices approaches 21% with a high open‐circuit voltage (1.148 V) and delivers a high stability of 89% after aging 60 days in atmosphere without encapsulation, which is the highest efficiency of organic electron transport layers for n–i–p PSCs.

The double‐sided surface passivation engineering is the use of phenethylammonium iodide to effectively passivate the top and bottom defects of Sn‐based perovskite films. The increase of grain size, the decrease in density of trap states, and the surface hydrophobicity effectively improve the sensitivity and stability of Sn‐based perovskite photodetectors. Finally, the photodetectors realize the infrared upconversion application.

Abstract

Tin(Sn)‐based perovskite is currently considered one of the most promising materials due to extending the absorption spectrum and reducing the use of lead (Pb). However, Sn²⁺ is easily oxidized to Sn⁴⁺ in atmosphere, causing more defects and degradation of perovskite materials. Herein, double‐sided interface engineering is proposed, that is, Sn‐Pb perovskite films are sandwiched between the phenethylammonium iodide (PEAI) in both the bottom and top sides. The larger organic cations of PEA+ are arranged into a perovskite surface lattice to form a 2D capping layer, which can effectively prevent the water and oxygen to destroy bulk perovskite. Meanwhile, the PEA+ can also passivate defects of iodide anions at the bottom of perovskite films, which is always present but rarely considered previously. Compared to one sided passivation, Sn‐Pb hybrid perovskite photodetectors contribute a significant enhancement of performance and stability, yielding a broadband response of 300–1050 nm, a low dark current density of 1.25 × 10^–3 mA cm^–2 at –0.1 V, fast response speed of 35 ns, and stability beyond 240 h. Furthermore, the Sn‐Pb broadband photodetectors are integrated in an infrared up‐conversion system, converting near‐infrared light into visible light. It is believed that a double‐sided passivation method can provide new strategies to achieving high‐performance perovskite photodetectors.

The undercoordinated ionic defects at heterojunction interfaces remain challenges that limit the performances and stability of perovskite photoelectric devices. A self‐phase separated doping strategy is developed to link multilayer heterojunction interfaces including both the energy level and trap states, paving a novel route for nonequilibrium distributed dopants to solve the key challenge of interface defects.

Abstract

In perovskite solar cells (PSCs), the interfaces of the halide perovskite/electron transport layer (ETL) and ETL/metal oxide electrode (MOE) always attract and trap free carriers via the surface electrostatic force, altering quasi‐Fermi level (E _Fq) splitting of contact interfaces, and significantly limit the charge extraction efficiency and intrinsic stability of devices. Herein, a graded “bridge” is first reported to link the MOE and perovskite interfaces by self vertical phase separation doping (PSD), diminishing the side effect of notorious ionic defects via both reinforced interface E _bi and the vacancies filling. Experimental and theoretical results prove that the inhomogeneous distribution of CsF in the bulk or surface of PC₆₁BM would not only form metal–oxygen (M–O) dipole on MOE, reinforcing the interface E _bi, but also create a graded energy bridge to alleviate the disadvantage of band offset raised by the enhanced interface E _bi, which significantly avoid the carrier accumulation and recombination at defective interfaces. Employing PSD, the power conversion efficiency of the devices approaches 21% with a high open‐circuit voltage (1.148 V) and delivers a high stability of 89% after aging 60 days in atmosphere without encapsulation, which is the highest efficiency of organic electron transport layers for n–i–p PSCs.