Ligang Yuan

The catastrophic failure of n-i-p type perovskite solar cells under operation is reported, which is proven by the corrosion of the metal electrode on the edge. After inserting a thin MoO₃, the improved Ag thin film morphology as well as better energy alignment suppress the catastrophic failure of perovskite solar cells.

Abstract

The n-i-p type perovskite solar cells suffer unpredictable catastrophic failure under operation, which is a barrier for their commercialization. The fluorescence enhancement at Ag electrode edge and performance recovery after cutting the Ag electrode edge off prove that the shunting position is mainly located at the edge of device. Surface morphology and elemental analyses prove the corrosion of the Ag electrode and the diffusion of Ag⁺ ions on the edge for aged cells. Moreover, much condensed and larger Ag clusters are formed on the MoO₃ layer. Such a contrast is also observed while comparing the central and the edge of the Ag/Spiro-OMeTAD film. Hence, the catastrophic failure mechanism can be concluded as photon-induced decomposition of the perovskite film and release reactive iodide species, which diffuse and react with the loose Ag clusters on the edge of the cell. The corrosion of the Ag electrode and the migration of Ag⁺ ions into Spiro-OMeTAD and perovskite films lead to the forming of conducting filament that shunts the cell. The more condensed Ag cluster on the MoO₃ surface as well as the blocking of holes within the Spiro-OMeTAD/MoO₃ interface successfully prevent the oxidation of Ag electrode and suppress the catastrophic failure.

A facile one-step method to in situ deposit γ-phase 3D CsPbI₃ films consisting of cuboid crystallites is achieved by introducing 1,3-propanediamine dihydriodide (PDAI). The PDAI–perovskite light-emitting diode (PeLED) can reach a record efficiency of 15.03% for 3D CsPbI₃ PeLEDs and a peak efficiency of 10.30% of a 9 cm² PeLED.

Abstract

Inorganic CsPbI₃ perovskite with high chemical stability is attractive for efficient deep-red perovskite light-emitting diodes (PeLEDs) with high color purity. Compared to PeLEDs based on ex-situ-synthesized CsPbI₃ nanocrystals/quantum dots suffering from low conductivity and efficiency droop under high current densities, in situ deposited 3D CsPbI₃ films from precursor solutions can maintain high conductivity but show high trap density. Here, it is demonstrated that introducing diammonium iodide can increase the size of colloids in the precursor solution, retard the phase-transition rate, and passivate trap states of the in-situ-formed cuboid crystallites. The PeLED based on the one-step-formed 3D CsPbI₃ cuboid crystallite films shows a peak external quantum efficiency (EQE) value up to 15.03% because of the high conductivity and reduced trap states. Furthermore, this one-step method also has a wide processing window, which is attractive for flow-line production of large-area PeLED modules. The fabrication of a 9 cm² PeLED that exhibits a peak EQE of 10.30% is successfully demonstrated.

Recent developments of the quinoxaline-based D–A copolymers for the applications as polymer donor in polymer solar cells and as hole transport material in perovskite solar cells are reviewed.

Abstract

Polymer solar cells (PSCs) have achieved great progress recently, benefiting from the rapid development of narrow bandgap small molecule acceptors and wide bandgap conjugated polymer donors. Among the polymer donors, the D–A copolymers with quinoxaline (Qx) as A-unit have received increasing attention since the report of the low-cost and high-performance D–A copolymer donor based on thiophene D-unit and difluoro-quinoxalline A-unit in 2018. In addition, the weak electron-deficient characteristic and the multiple substitution positions of the Qx unit make it an ideal A-unit in constructing the wide bandgap polymer donors with different functional substitutions. In this review article, recent developments of the Qx-based D–A copolymer donors, including synthetic method of the Qx unit, backbone modulation, side chain optimization, and functional substitution of the Qx-based D–A copolymers, are summarized and discussed. Furthermore, the application of the Qx-based D–A copolymers as hole transport material in perovskite solar cells (pero-SCs) is also introduced. The focus mainly on the molecular design strategies and structure–properties relationship of the Qx-based D–A copolymers, aiming to provide a guideline for developing high-performance Qx-based D–A copolymers for the applications as donor in PSCs and as hole transport material in pero-SCs.

Nature Communications, Published online: 06 October 2021; doi:10.1038/s41467-021-26121-1

Perovskite photovoltaics has become more competitive against silicon counterpart in reducing cost of solar energy, yet the management of toxic lead hampers it application. Here, the authors propose a cost-effective environmental-friendly approach to recycle lead and transparent conductors.

To understand the nature of hysteresis, theoretical mechanisms and experimental measurements are provided based on a combination of first-principles simulations, cross-section scanning electron microscopy images, and time-dependent photocurrent measurements. The defect assistance ion-migration process could be the primary contribution to hysteresis. The defect density is reduced via the in situ passivation of PbI₂ crystals, which prevents the migration of ions effectively, and the hysteresis index is decreased from 22.43% to 1.04%.

Abstract

As one of the most promising photovoltaic materials, the efficiency of inorganic–organic hybrid halide perovskite solar cells (PSCs) has reached 25.5% in 2020. However, the stability and hysteresis remain primary challenges before it can become a commercial photovoltaic technology. Therefore, those issues have drawn significant attention for photovoltaic applications. In this work, a study of the PSCs hysteresis improvement is presented based on a combination of first-principles simulations, scanning electron microscopy images, and time-dependent photocurrent measurements. It indicates the hysteresis led by the ion migration and accumulation is mainly localized at the two interfaces: one is between electron transport layer and active layer, and the other is between active layer and hole transport layer. Considering the massive defects at the grain boundaries (GBs), they lower the potential barriers significantly. The defect density at GBs is therefore reduced via the in situ passivation of PbI₂ crystals. The hysteresis index is decreased from 22.43% down to 1.04%, and results in an improvement in efficiency from 17.12% up to 20.10%. Following the understanding of defect-induced hysteresis, an approach to improve the hysteresis is provided, which can be integrated into the fabrication process and widely applied to enhance the performance of PSCs.

The electron transport layer (ETL) plays a crucial part in extracting electrons and optimizing interfacial contact for perovskite solar cells (PVSCs). Herein, the EVA is introduced into PC₆₁BM to promote the orderly molecular stacking of ETLs. The PC₆₁BM:EVA-based MAPbI₃ PVSCs deliver a champion efficiency of 19.32% and regain 80% of initial efficiency after storage under 52% humidity for 1500 h.

Abstract

The electron transport layer (ETL) plays a crucial part in extracting electron carriers while optimizing the interfacial contact of perovskite/electrode in planar heterojunction perovskite solar cells (PVSCs). Despite various ETLs being designed for efficient PVSCs, there exists hardly any research on the effect of molecular stacking order on device performance. Herein, poly(ethylene-co-vinyl acetate) (EVA) is employed as the [6,6]-phenyl-C₆₁-butyric acid methyl ester (PC₆₁BM) solution additive. The strong binding energy between EVA with PC₆₁BM promotes the molecular stacking order of ETLs, which alleviates the morphology inhomogeneity, possesses a matched energy level, blocks ion migration, and improves the water–oxygen barrier of perovskite devices. The blade-coated MAPbI₃-based PVSCs achieve a power conversion efficiency (PCE) of 19.32% with positive reproducibility and negligible hysteresis, as well as maintain 90% and 80% of the initial PCE after storage under inert and ambient conditions (52% humidity) for 1500 h without encapsulation. This strategy also improves the champion PCE of CsFAMA-based PVSCs to 20.33%. These findings demonstrate that the regulation of molecular stacking order is a valid approach to optimize interfacial charge-carrier recombination in PVSCs, which meet the demand for high-performance ETL in large-area PVSCs and improve the upscaling of the fabrication technology toward practical applications.

A flexible hybrid solar cell with extended photoresponse, high power conversion efficiency of 21.73%, and excellent mechanical durability is realized by incorporating a low-bandgap organic bulk heterojunction layer into perovskite solar cells. Taking advantage of these impressive device performance, the flexible solar cell–sensor integrated system is demonstrated for real-time temperature monitoring via on-body evaluation.

Abstract

Lead halide perovskite and organic solar cells (PSCs and OSCs) are considered as the prime candidates currently for clean energy applications due to their solution and low-temperature processibility. Nevertheless, the substantial photon loss in near-infrared (NIR) region and relatively large photovoltage deficit need to be improved to enable their uses in high-performance solar cells. To mitigate these disadvantages, low-bandgap organic bulk-heterojunction (BHJ) layer into inverted PSCs to construct facile hybrid solar cells (HSCs) is integrated. By optimizing the BHJ components, an excellent power conversion efficiency (PCE) of 23.80%, with a decent open-circuit voltage (V _oc) of 1.146 V and extended photoresponse over 950 nm for rigid HSCs is achieved. The resultant devices also exhibit superior long-term (over 1000 h) ambient- and photostability compared to those from single-component PSCs and OSCs. More importantly, a champion PCE of 21.73% and excellent mechanical durability can also be achieved in flexible HSCs, which is the highest efficiency reported for flexible solar cells to date. Taking advantage of these impressive device performances, flexible HSCs into a power source for wearable sensors to demonstrate real-time temperature monitoring are successfully integrated.

How to obtain and understand in situ GIWAXS data is highlighted, and recent results of in situ GIWAXS studies on versatile perovskite photovoltaic systems that elucidate crystallization and film formation mechanisms in terms of material compositions, film deposition methods, and film treatment procedures are summarized and assessed.

Abstract

Metal halide perovskites are of fundamental interest in the research of modern thin-film optoelectronic devices, owing to their widely tunable optoelectronic properties and solution processability. To obtain high-quality perovskite films and ultimately high-performance perovskite devices, it is crucial to understand the film formation mechanisms, which, however, remains a great challenge, due to the complexity of perovskite composition, dimensionality, and processing conditions. Nevertheless, the state-of-the-art in situ grazing-incidence wide-angle X-ray scattering (GIWAXS) technique enables one to bridge the complex information with device performance by revealing the crystallization pathways during the perovskite film formation process. In this review, the authors illustrate how to obtain and understand in situ GIWAXS data, summarize and assess recent results of in situ GIWAXS studies on versatile perovskite photovoltaic systems, aiming at elucidating the distinct features and common ground of film formation mechanisms, and shedding light on future opportunities of employing in situ GIWAXS to study the fundamental working mechanisms of highly efficient and stable perovskite solar cells toward mass production.

This study introduces an octyl-diammonium lead iodide (ODAPbI₄) interlayer onto the hole-transporting layer, which significantly reduces nonradiative recombination of wide-bandgap perovskite devices, enhancing the efficiency of wide-bandgap devices beyond 21%. By coupling a semitransparent device with a Cu₂ZnSn(S,Se)₄ (CZTSSe) cell, a four terminal perovskite/CZTSSe tandem cell with a power conversion efficiency of 22.27% is achieved.

Abstract

Wide-bandgap perovskites have attracted substantial attention due to their important role in serving as a top absorber in tandem solar cells (TSCs). However, wide-bandgap perovskite solar cells (PVSCs) typically suffer from severe non-radiative recombination loss and therefore exhibit high open-circuit voltage (V _OC) deficits. To address these issues, a 2D octyl-diammonium lead iodide interlayer is adopted onto the hole-transporting layer to induce the formation of an ultrathin quasi-2D perovskite that is close to the hole-selective interface. This approach not only accelerates hole transfer and retards hole accumulation but also reduces the trap density in the perovskite layer on top, thereby efficiently suppresses non-radiative recombination pathways. Consequently, the champion wide-bandgap device (≈1.66 eV) exhibits a power conversion efficiency (PCE) of 21.05% with a V _OC of 1.23 V, where the V _OC deficit of 0.43 V is among the lowest values for inverted wide-bandgap PVSCs. Moreover, by stacking a semi-transparent perovskite top cell on a 1.1 eV Cu₂ZnSn(S,Se)₄ (CZTSSe) bottom cell, a 22.27% PCE was achieved on a perovskite/CZTSSe four-terminal tandem solar cell, paving the way for all-solution-processed, low-cost, and efficient TSCs with mitigated energy loss in the wide-bandgap top cells.

Nature Photonics, Published online: 06 September 2021; doi:10.1038/s41566-021-00857-0

The use of metal–organic frameworks helps protect perovskite nanocrystals, resulting in bright, stable light-emitting diodes.

A novel catalytic heterojunction made of Cs₃Bi₂Br₉ and g-C₃N₄ is reported. The good band alignment between the two semiconductors provides the path to improve the carrier dynamics, and to promote a synergic effect resulting in improved photocatalytic hydrogen evolution and organic dye degradation reactions.

Abstract

The rational design of heterojunctions based on metal halide perovskites (MHPs) is an effective route to create novel photocatalysts to run relevant solar-driven reactions. In this work, an experimental and computational study on the synergic coupling between a lead-free Cs₃Bi₂Br₉ perovskite derivative and g-C₃N₄ is presented. A relevant boost of the hydrogen photogeneration by more than one order of magnitude is recorded when going from pure g-C₃N₄ to the Cs₃Bi₂Br₉/g-C₃N₄ system. Effective catalytic activity is also achieved in the degradation of the organic pollutant with methylene blue as a model molecule. Based upon complementary experimental outputs and advanced computational modeling, a rationale is provided to understand the heterojunction functionality as well as the trend of hydrogen production as a function of perovskite loading. This work adds further solid evidence for the possible application of MHPs in photocatalysis, which is emerging as an extremely appealing and promising field of application of these superior semiconductors.

Interfacial nonradiative recombination limits the open-circuit voltage of perovskite solar cells. A buried interface passivation strategy is developed that can be used across metal oxide transport layers. Perovskite precursors containing large organic cations with high affinity for the substrate spontaneously form a 2D passivation layer on the underlying metal oxides, which reduces interfacial recombination by 72%.

Abstract

The open-circuit voltage (V _oc) of perovskite solar cells is limited by non-radiative recombination at perovskite/carrier transport layer (CTL) interfaces. 2D perovskite post-treatments offer a means to passivate the top interface; whereas, accessing and passivating the buried interface underneath the perovskite film requires new material synthesis strategies. It is posited that perovskite ink containing species that bind strongly to substrates can spontaneously form a passivating layer with the bottom CTL. The concept using organic spacer cations with rich NH₂ groups is implemented, where readily available hydrogens have large binding affinity to under-coordinated oxygens on the metal oxide substrate surface, inducing preferential crystallization of a thin 2D layer at the buried interface. The passivation effect of this 2D layer is examined using steady-state and time-resolved photoluminescence spectroscopy: the 2D interlayer suppresses non-radiative recombination at the buried perovskite/CTL interface, leading to a 72% reduction in surface recombination velocity. This strategy enables a 65 mV increase in V _oc for NiO _x based p–i–n devices, and a 100 mV increase in V _oc for SnO₂-based n–i–p devices. Inverted solar cells with 20.1% power conversion efficiency (PCE) for 1.70 eV and 22.9% PCE for 1.55 eV bandgap perovskites are demonstrated.

Publication date: 17 November 2021

Source: Joule, Volume 5, Issue 11

Author(s): Igal Levine, Amran Al-Ashouri, Artem Musiienko, Hannes Hempel, Artiom Magomedov, Aida Drevilkauskaite, Vytautas Getautis, Dorothee Menzel, Karsten Hinrichs, Thomas Unold, Steve Albrecht, Thomas Dittrich

Organic molecule dopants of fluorophenylboronic acids (F-PBAs) act as crystal cross-linkers between neighboring perovskite grains through hydrogen bonding and coordination bonding, yielding high-quality perovskite films with reduced grain boundary defects. Benefiting from the effective perovskite crystal cross-linking, a remarkable augmentation of the efficiency from 16.4% to nearly 20% has been achieved, while simultaneously enhancing moisture/thermal/light stability of MAPbI₃-based PSCs.

Abstract

Organic-inorganic metal halide perovskites are regarded as one of the most promising candidates in the photovoltaic field, but simultaneous realization of high efficiency and long-term stability is still challenging. Here, a one-step solution-processing strategy is demonstrated for preparing efficient and stable inverted methylammonium lead iodide (MAPbI₃) perovskite solar cells (PSCs) by incorporating a series of organic molecule dopants of fluorophenylboronic acids (F-PBAs) into perovskite films. Studies have shown that the F-PBA dopant acts as a cross-linker between neighboring perovskite grains through hydrogen bonds and coordination bonds between F-PBA and perovskite structures, yielding high-quality perovskite crystalline films with both improved crystallinity and reduced defect densities. Benefiting from the repaired grain boundaries of MAPbI₃ with the organic cross-linker, the inverted PSCs exhibit a remarkably enhanced performance from 16.4% to approximately 20%. Meanwhile, the F-PBA doped devices exhibit enhanced moisture/thermal/light stability, and specially retain 80% of their initial power conversion efficiencies after more than two weeks under AM 1.5G one-sun illumination. This work highlights the impressive advantages of the perovskite crystal cross-linking strategy using organic molecules with strong intermolecular interactions, providing an efficient route to prepare high-performance and stable planar PSCs.

A synergetic device architecture is proposed for minimizing Joule heating in perovskite light-emitting diodes toward high efficiency and long lifetime. By reducing the driving current and suppressing light re-absorption in the perovskite emitter, the red-emission device achieves a peak external quantum efficiency of 21.2% and an operational half-lifetime of 4806.7 h.

Abstract

Regardless of the rapid advance on perovskite light-emitting diodes (PeLEDs), the lack of long-term operational stability hinders the practicality of this technology. Particularly, thermal management is indispensable to control the Joule heating induced by charge transport and parasitic re-absorption of internally confined photons. Herein, a synergetic device architecture is proposed for minimizing the optical energy losses in PeLEDs toward high efficiency and long lifetime. By adopting a carefully modified perovskite emitter in combination with an improved light outcoupling structure, red PeLEDs emitting at 666 nm achieve a peak external quantum efficiency of 21.2% and an operational half-lifetime of 4806.7 h for an initial luminance of 100 cd m^-2. The enhanced light extraction from trapped modes can efficiently reduce the driving current and suppress optical energy losses in PeLEDs, which in turn ameliorate the heat-induced device degradation during operation. This work paves the way toward high-performance PeLEDs for display and lighting applications in the future.

In situ conversion of a 2D templating layer is used to fabricate lead-tin perovskite films highly ordered and with stoichiometric composition. The obtained highly crystalline lead-tin perovskites possess much enhanced environmental stability and promising photovoltaic performance, offering a considerable prospect to accelerate the commercialization of perovskite solar cells.

Abstract

Low bandgap lead-tin halide perovskites are predicted to be candidates to maximize the performance of single junction and tandem solar cells based on metal halide perovskites. In spite of the tremendous progress in lab-scale device efficiency, devices fabricated with scalable techniques fail to reach the same efficiencies, which hinder their potential industrialization. Herein, a method is proposed that involves a template of a 2D perovskite deposited with a scalable technique (blade coating), which is then converted in situ to form a highly crystalline 3D lead-tin perovskite. These templated grown films are alloyed with stoichiometric ratio and are highly oriented with the (l00) planes aligning parallel to the substrate. The low surface/volume ratio of the obtained single-crystal-like films contributes to their enhanced stability in different environments. Finally, the converted films are demonstrated as active layer for solar cells, opening up the opportunity to develop this scalable technique for the growth of highly crystalline hybrid halide perovskites for photovoltaic devices.

The 1-pyrenesulfonic acid sodium salt (PyNa⁺) is used to double-sided passivate the perovskite film to obtain a high device performance. By top-bottom management, the carrier lifetimes are prolonged and the defect density is effectively reduced. The device delivers a high efficiency of 21.22% and excellent stability holding 85% of its original efficiency after 1440 h in atmospheric environment.

In perovskite solar cells, not only defects on the top perovskite film surface seriously affect device performance, those buried in the bottom perovskite–electron-transfer layer (ETL) interface damage carrier extraction, transport, and device efficiency as well. Herein, a novel double-sided passivation strategy is designed using a single π-conjugation-induced 1-pyrenesulfonic acid sodium salt (PyNa⁺). It is found that it effectively passivates top and bottom interface defects to render high device performance. The π-conjugated pyrene-containing sodium salt electronically contributes to the surface band edges and influences the carrier dynamics by passivating defects at both top hole-transfer layer (HTL)–perovskite and bottom perovskite–ETL interfaces. The density functional theory (DFT) calculation confirms that the Pb cluster and I—Pb antisite defects can be effectively passivated by the O···Pb coordination and electrostatic interaction of PyNa⁺. The carrier lifetimes are prolonged, the interface defect density is effectively reduced as measured by space-charge-limited current (SCLC). Through the double layer passivation of PyNa⁺, the device delivers improved power conversion efficiencies of 21.22% relative to that of a reference perovskite, and enhanced stability with 85% of original efficiency after 1440 h in atmospheric environment. Double-sided passivation provides a comprehensive strategy for high-performance perovskite solar cells.

An environmentally benign material, histamine (HA), is used to intentionally passivate the V_I in the CsPbI_3−x Br _x perovskite thin films. The synergistic effect of Lewis base–acid interaction and H-bond strengthens the adsorption of HA molecules on the surface of perovskite. The fabricated PSCs with HA passivation significantly reduced the number of uncoordinated Pb²⁺ and achieved a record 20.8 % efficiency.

Abstract

Iodine vacancies (V_I) and undercoordinated Pb²⁺ on the surface of all-inorganic perovskite films are mainly responsible for nonradiative charge recombination. An environmentally benign material, histamine (HA), is used to passivate the V_I in perovskite films. A theoretical study shows that HA bonds to the V_I on the surface of the perovskite film via a Lewis base–acid interaction; an additional hydrogen bond (H-bond) strengthens such interaction owing to the favorable molecular configuration of HA. Undercoordinated Pb²⁺ and Pb clusters are passivated, leading to significantly reduced surface trap density and prolonged charge lifetime within the perovskite films. HA passivation also induces an upward shift of the energy band edge of the perovskite layer, facilitating interfacial hole transfer. The combination of the above raises the solar cell efficiency from 19.5 to 20.8 % under 100 mW cm⁻² illumination, the highest efficiency so far for inorganic metal halide perovskite solar cells (PSCs).

Publication date: 15 December 2021

Source: Chemical Engineering Journal, Volume 426

Author(s): Xiaohui Ma, Liqun Yang, Xueni Shang, Mengjia Li, Deyu Gao, Cuncun Wu, Shijian Zheng, Boxue Zhang, Jiangzhao Chen, Cong Chen, Hongwei Song

A novel charge separation reversion mechanism is proposed for fabricating perovskite dual-band photodetectors, which show negative broadband responses in the above-bandgap region and positive narrowband responses in the sub-bandgap region. The positive response peak can be tailored from 410 to 675 nm by adjusting the bandgap of perovskites. The dual-band photodetectors are successfully applied to simulate traffic signal recognition.

Abstract

New mechanisms and modalities for multiband light detection are highly desirable for the ever-growing developments in machine vision technologies. Demonstrated here is a unique talent of halide perovskites for making self-driven dual-band photodetectors with a negative broadband response in the above-bandgap absorption region and a positive narrowband response in the sub-bandgap absorption region. The device operates through a charge separation reversion mechanism by controlling the built-in electric field and the thickness-dependent light absorption profile in the active material. Impressively, the demarcation wavelengths between the negative broadband and the positive narrowband responses can be continuously adjusted, with the positive narrowband response easily tuned from 410 to 675 nm. The dual-band photodetector exhibits an extremely low noise of 10⁻¹⁵ A Hz^−1/2 and a high specific detectivity of >10¹² Jones in both above-bandgap and sub-bandgap absorption regions, opening up application opportunities in intelligent recognition and biomedical diagnosis.

An underlayer with a bilayer structure of 2,2′,7,7′-tetrakis(N,N-dip-methoxyphenylamine)-9,9′-spirobifluorene and copper phthalocyanine 3,4′,4″,4′″-tetrasulfonated acid tetrasodium salt is applied to inverted CsPbI₂Br perovskite solar cells (PeSCs). As a result, the PeSCs with improved photovoltaic performance and stability can be achieved due to the reduced defect density as well as mitigated interfacial tensile strain.

Abstract

Inorganic perovskite CsPbI₂Br has advantages of excellent thermal stability and reasonable bandgap, which make it suitable for top layer of tandem solar cells. Nevertheless, solution-processed all-inorganic perovskites generally suffer from high-density defects as well as significant tensile strain near underlayer/perovskite interface, both leading to compromised device efficiency and stability. In this work, the defect density as well as interfacial tensile strain in inverted CsPbI₂Br perovskite solar cells (PeSCs) is remarkably reduced by using a bilayer underlayer composed of dopant-free 2,2′,7,7′-tetrakis(N,N-dip-methoxyphenylamine)-9,9′-spirobifluorene (Spiro-OMeTAD) and copper phthalocyanine 3,4′,4″,4′″-tetrasulfonated acid tetrasodium salt (TS-CuPc) nanoparticles. As compared to control devices with pristine Spiro-OMeTAD, devices based on Spiro-OMeTAD/TS-CuPc exhibit remarkably improved photovoltaic performance and enhanced thermal/humidity stability due to the better perovskite crystallization, improved interfacial passivation, and hole-collection as well as efficient interfacial strain release. As a result, a champion efficiency of 14.85% can be achieved, which is approaching to the best reported for dopant-free and inverted all-inorganic PeSCs. The work thus provides an efficient strategy to simultaneously regulate the defects density and strain issue related to inorganic perovskites.

A facile strategy is developed to achieve high-quality perovskite light emitting diode (PeLED) by inkjet-printing perovskite precursor solution. Here, by incorporating an interface polyvinylpyrrolidone layer and adjusting the temperature of the printing substrate, the coffee-stain effect is effectively inhibited. Finally, an inkjet-printed PeLED with a brightness of 3640 cd m^–2 and external quantum efficiency of 9.0% was achieved.

Abstract

Inkjet printing is a powerful technology for realizing high-density pixelated perovskite light-emitting diodes (PeLEDs). However, the coffee-stain effect in the inkjet printing process often leads to uneven thickness and poor crystallization of printed perovskite features, which deteriorates the performance of PeLEDs. Here, a strategy is developed to suppress the coffee-stain effect via enhancing Marangoni flow strength. An interfacial poly(vinylpyrrolidone) (PVP) layer is incorporated to tune the surface tension of the underlying hole transport layer (HTL) and enhance the perovskite crystallization. The substrate temperature is also carefully controlled to tune the printing solvent evaporation rate rationally. By optimizing the thickness of the PVP layer and the temperature of the printing stage, the coffee-stain effect is dramatically restrained. In addition, the interfacial insulating PVP layers play a positive role in suppressing leakage current level of PeLEDs by avoiding any direct electrical contact between HTL and electron transporting layer. Finally, an inkjet-printed PeLED with a brightness of 3640 cd m^–2 and external quantum efficiency of 9.0% is achieved. This work highlights the availability of inkjet-printing technology for fabricating patterned PeLEDs in information display applications.

An efficient blue emitting all-inorganic double perovskite Cs₂NaScCl₆ is synthesized by using a cooling-induced crystallization method. Mn²⁺ ions can be efficiently doped into the lattice of Cs₂NaScCl₆, leading to tunable dual broadband emission, a blue emission from the host and a red emission from Mn²⁺ transitions. The emission mechanism is revealed by using a series of spectroscopic techniques.

Abstract

Halide double perovskites have been regarded as promising alternatives to famous lead halide perovskites in the field of luminescent materials. However, the low-emission efficiency of pristine ones and the lack of efficient blue emitters remain considerable obstacles for their applications in light-emitting devices. Here, an air-stable, all-inorganic Sc-based double perovskite Cs₂NaScCl₆ is reported, which exhibits strong blue emission peaking at 445 nm with an averaged quantum yield of 29.05% (the highest reported value for pristine halide double perovskites). The rare-earth double perovskite also shows excellent stability against heat and irradiation. Bulk perovskite Cs₂NaScCl₆ can be an effective host to incorporate Mn²⁺ ions, yielding interesting tunable dual broadband emission, slightly redshifted blue emission (450 nm) from the host and red emission (635 nm) from Mn²⁺ d–d transitions. These findings present a new direction toward the design of high-efficiency, stable, and environmentally friendly perovskite light emitters.