JIALINGBO

The successfully synthesized lead-free 0D manganese-based (Mn-based) organic–inorganic hybrid perovskite exhibits a bright and pure red emission with a high photoluminescence quantum yield. After optimization, the maximum recording brightness of Mn-based perovskite light-emitting diodes (PeLEDs) is 4700 cd m⁻², and the peak external quantum efficiency is 9.8%, surpassing all reported lead-free PeLEDs.

Abstract

Lead-based perovskite light-emitting diodes (PeLEDs) have exhibited excellent purity, high efficiency, and good brightness. In order to develop nontoxic, highly luminescent metal halide perovskite materials, tin, copper, germanium, zinc, bismuth, and other lead-free perovskites have been developed. Here, a novel 0D manganese-based (Mn-based) organic–inorganic hybrid perovskite with the red emission located at 629 nm, high photoluminescence quantum yield of 80%, and millisecond level triplet lifetime is reported. When applied as the emissive layer in the PeLEDs, the maximum recording brightness of devices after optimization is 4700 cd m⁻², and the peak external quantum efficiency is 9.8%. The half-life of the device reaches 5.5 h at 5 V. The performance and stability of Mn-based PeLEDs are one order of magnitude higher than those of other lead-free PeLEDs. This work clearly shows that the Mn-based perovskite will provide another route to fabricate stable and high-performance lead-free PeLEDs.

Fluoroethylamine passivates defects in perovskite films as a result of F distribution throughout the bulk and even at the surface. The nonradiative recombination in perovskite films using derivatives of this compound is suppressed, the carrier-lifetime is prolonged, and the film–air interface offers greater hydrophobicity. The corresponding solar cells deliver high efficiency of up to 23.40%. The unencapsulated device shows good environmental stability, maintaining 87% of its initial efficiency after exposure to the ambient environment for 1200 h.

Abstract

Defects in perovskite layers usually cause nonradiative recombination, impairing device performance and stability. Here, fluoroethylamine (FC₂H₄NH₃, FEA) is integrated into the perovskite film to passivate defects. By engineering of different amounts of fluorine in the molecule, it is found that when 2-fluoroethylamine (1FEA), in which one F bonds to the first carbon atom at the end of the molecule's structure, is used, the F atoms appear to be distributed throughout the bulk to the very surface. When 2,2-difluoroethylamine (2FEA) and 2, 2, 2-trifluoroethylamine (3FEA) are used, F is prone to distribution in the bulk of the perovskite film, while there appears to be no detectable F content on the surface. With the FEA passivation, the nonradiative recombination is suppressed, the carrier-lifetime is improved to 840.01 ns, and the film-air interface offers greater hydrophobicity, especially in the case of 1FEA, where because it is distributed throughout the film thickness, it passivates more defects and delivers the highest efficiency, as much as 23.40%. The device with 3FEA shows the best environmental stability; specifically, the bare cell without any encapsulation maintains 87% of its initial efficiency after exposure to the ambient environment for 1200 h.

Herein, perovskite defects are categorized into two big groups of halide and cation vacancies. The defect passivation methods are divided into bulk and surface treatment of perovskite films. All kinds of passivating agent materials are classified based on their functional groups for defect passivation. Finally, a comprehensive perspective for achieving high-performance and stable perovskite solar cells is provided.

Perovskite solar cells (PSCs) have been introduced as an attractive photovoltaic technology over the past decade due to their low-cost processing, earth-abundant raw materials, and high power conversion efficiencies (PCEs) of up to 25.2%. However, the relatively high density of defects within the bulk, grain boundaries, and surface of polycrystalline perovskite films acts as recombination centers and facilitates ion migration, lowering the theoretical PCE ceiling, often leading to inferior device stability. Therefore, understanding the defect sources and developing passivation methods are key factors for reaching higher PCEs and stabilities in perovskite photovoltaics. Herein, various passivation methods, including bulk and surface treatment of perovskite films, are explored. In the bulk treatment, the passivating agents should be directly added to the perovskite precursor. However, in the surface treatment method, the surface of perovskite films can be treated by inducing passivating agents during the intermediate phase or after annealing steps, denoted here as in-film or surface posttreatment. In addition, different kinds of passivating agents are categorized based on their functional groups. Finally, the outline directions to minimize the defects in perovskite films are highlighted.

The Sn-Pb alloyed perovskite films with stable α -phase and oxidation resistance are prepared by bulk doping (CsCl) and surface coordination (PbSO₄). The less oxidation of Sn²⁺ and enhanced stability are caused by reconfiguring perovskite crystallization and the formed dense water-insoluble hydrophobic surface. The ultimately fabricated perovskite solar cells deliver a champion power conversion efficiency of 10.39% and excellent stability.

Abstract

Novel all-inorganic Sn-Pb alloyed perovskites are developed aiming for low toxicity, low bandgap, and long-term stability. Among them, CsPb_{1− x} Sn _x I₂Br is predicted as an ideal perovskite with favorable band gap, but previously is demonstrated unable to convert to perovskite phase by thermal annealing. In this report, a series of CsPb_{1− x} Sn _x I₂Br perovskites with tunable bandgaps from 1.92 to 1.38 eV are successfully prepared for the first time via low annealing temperature (60 °C). Compared to the pure CsPbI₂Br, these Sn-Pb alloyed perovskites show superior stability. Furthermore, a novel α-phase-stabilization mechanism of the inorganic Sn-Pb alloyed perovskite by reconfiguring the perovskite crystallization process with chloride doping is provided. Simultaneously, a dense protection layer is formed by the coordination reaction between the surface lead dangling bonds and sulfate ion to retard the permeation of external oxygen and moisture, leading to less oxidation of Sn²⁺ in perovskite film. As a result, the fabricated all-inorganic Sn-Pb perovskite solar cells (PSCs) show a champion power conversion efficiency of 10.39% with improved phase stability and long-term ambient stability against light, heat, and humidity. This work provides a viable strategy in fabricating high-performance narrow-bandgap all-inorganic PSCs.

In-depth insights into the roles of tin fluoride (SnF₂) additive in low-bandgap mixed tin (Sn)-lead (Pb) perovskite and efficient solar cells are provided. The growth mode of the film, highly oriented topological growth, and reduced Sn²⁺ oxidation are achieved via proper SnF₂ doping. Additionally, the accumulation of F⁻ at hole transport layer/perovskite interface is shown at higher SnF₂ content, leading to more defects.

Abstract

Low-bandgap mixed tin–lead perovskite solar cells (PSCs) have been attracting increasing interest due to their appropriate bandgaps and promising application to build efficient all-perovskite tandem cells, an effective way to break the Shockley–Queisser limit of single-junction cells. Tin fluoride (SnF₂) has been widely used as a basis along with various strategies to improve the optoelectronic properties of low-bandgap SnPb perovskites and efficient cells. However, fully understanding the roles of SnF₂ in both films and devices is still lacking and fundamentally desired. Here, the functions of SnF₂ in both low-bandgap (FASnI₃)_0.6(MAPbI₃)_0.4 perovskite films and efficient devices are unveiled. SnF₂ regulates the growth mode of low-bandgap SnPb perovskite films, leading to highly oriented topological growth and improved crystallinity. Meanwhile, SnF₂ prevents the oxidation of Sn²⁺ to Sn⁴⁺ and reduces Sn vacancies, leading to reduced background hole density and defects, and improved carrier lifetime, thus largely decreasing nonradiative recombination. Additionally, the F⁻ ion preferentially accumulates at hole transport layer/perovskite interface with high SnF₂ content, leading to more defects. This work provides in-depth insights into the roles of SnF₂ additives in low-bandgap SnPb films and devices, assisting in further investigations into multiple additives and approaches to obtain efficient low-bandgap PSCs.

Regarding the bottlenecks of defect density and ion migration at grain boundary within mixed halide perovskites, the profound superiorities brought by pyridinic nitrogen-doped graphdiyne (N-GDY) are systematically highlighted. It is proposed that the spatial confinement coupling with the electrostatic repulsion effect, induced by the intrinsic 2D structure of N-GDY, contributes to the conclusive capability of impeding the halide ion migration.

Abstract

The solution processing in hybrid perovskite films inevitably results in the formation of detrimental defects at grain boundaries (GBs) that deteriorate the optoelectronic properties and bring about severe hysteresis as well as operational instability. Here, an effective scenario to alleviate the imperfection issue at perovskite GBs via incorporating pyridinic nitrogen-doped graphdiyne (N-GDY) is proposed. Taking full advantage of periodic acetylenic linkages and introduced pyridinic N atoms, the deep-level trap states like Pb–I antisite defects and under-coordinated Pb atoms are considerably passivated, thus diminishing the undesired non-radiative recombination. Additionally, the spatial confinement coupling with electrostatic repulsion effect originated from the intrinsic 2D structure of N-GDY, has been identified to deal with the halide ion migration behavior. Such contributions are further theoretically evidenced with the charge density delocalization as well as the ion migration energy barrier elevation. The authors unprecedentedly verified the superiorities based on the flexible chemical-tailorability of atomic crystal GDY materials toward polycrystalline perovskite related energy conversion devices.

Molecular hole-transporting materials with different anchoring groups are synthesized. The anchoring groups with a stronger bonding strength enable greatly enhanced compactness of self-assembly monolayer, which benefits hole-extraction and electron-blocking in complete devices. When applied in inverted perovskite solar cells, 1 cm² devices show a promising power conversion efficiency of over 20% with high stability.

Abstract

Anchoring-based self-assembly (ASA) has emerged as a material-saving and highly scalable strategy to fabricate charge-transporting monolayers for perovskite solar cells (PSCs). However, the interfacial hole-extraction and electron-blocking performances are highly dependent on the compactness of the ASA monolayers, which has been largely ignored though it is very crucial to the efficiency and stability of PSCs. Here, strategically designed hole-transporting molecules with different anchoring groups are incorporated to investigate the effect of bonding strength on monolayer quality and correlate these with the performance of p-i-n structured PSCs. It is unraveled that the anchoring groups with a stronger bonding strength are advantageous for improving the assembly rate, density, and compactness of ASA monolayer, thus enhancing charge collection and suppressing interfacial recombination. The prototypical PSCs based on optimal ASA monolayer achieve a high power conversion efficiency (PCE) of 21.43% (0.09 cm²). More encouragingly, when enlarging the device area by tenfold, a comparable PCE of 20.09% (1.0 cm²) can be obtained, suggesting that the ASA strategy is practically useful for scaling-up. The robust anchoring of the ASA monolayer also enhances devices stability, retaining 90% of initial PCE after three months. This study provides important insights into the ASA charge-transporting monolayers for efficient and stable PSCs.

Newly synthesized hexabenzocoronene (HBC)–osmapentalyne complexes that combine fragments of graphene and metalla-aromatics are emerging as cathode interlayer materials. Further extending the d_π –p_π conjugated systems of osmapentalynes, the most successful complex, in this work, HBC-S is found to boost the efficiency of non-fullerene solar cells to over 18%.

Abstract

Interface engineering is a critical method by which to efficiently enhance the photovoltaic performance of nonfullerene solar cells (NFSC). Herein, a series of metal–nanographene-containing large transition metal involving d_π –p_π conjugated systems by way of the addition reactions of osmapentalynes and p-diethynyl-hexabenzocoronenes is reported. Conjugated extensions are engineered to optimize the π-conjugation of these metal–nanographene molecules, which serve as alcohol-soluble cathode interlayer (CIL) materials. Upon extension of the π-conjugation, the power conversion efficiency (PCE) of PM6:BTP-eC9-based NFSCs increases from 16% to over 18%, giving the highest recorded PCE. It is deduced by X-ray crystallographic analysis, interfacial contact methods, morphology characterization, and carrier dynamics that modification of hexabenzocoronenes-styryl can effectively improve the short-circuit current density (J _sc) and fill factor of organic solar cells (OSCs), mainly due to the strong and ordered charge transfer, more matching energy level alignments, better interfacial contacts between the active layer and the electrodes, and regulated morphology. Consequently, the carrier transport is largely facilitated, and the carrier recombination is simultaneously impeded. These new CIL materials are broadly able to enhance the photovoltaic properties of OSCs in other systems, which provides a promising potential to serve as CILs for higher-quality OSCs.

Ultra-deep-blue aggregation-induced delayed fluorescence emitters (TB-tCz and TB-tPCz) bearing organoboron-based core and carbazole derivatives are developed. Solution-processed nondoped organic light-emitting diodes (OLEDs) based on TB-tPCz exhibit a record external quantum efficiency of 15.8% with Commission international de l'éclairage color coordinates of (0.16, 0.05). Furthermore, both emitters also exhibit excellent device performances in solution-processed doped OLEDs.

Abstract

Ultra-deep-blue aggregation-induced delayed fluorescence (AIDF) emitters (TB-tCz and TB-tPCz) bearing organoboron-based cores as acceptors and 3,6-substituted carbazoles as donors are presented. The thermally activated delayed fluorescence (TADF) properties of the two emitters are confirmed by theoretical calculations and time-resolved photoluminescence experiments. TB-tCz and TB-tPCz exhibit fast reverse intersystem crossing rate constants owing to efficient spin–orbit coupling between the singlet and triplet states. When applied in solution-processed organic light-emitting diodes (OLEDs), the TB-tCz- and TB-tPCz-based nondoped devices exhibit ultra-deep-blue emissions of 416–428 nm and high color purity owing to their narrow bandwidths of 42.2–44.4 nm, corresponding to the Commission International de l´Eclairage color coordinates of (x = 0.16–0.17, y = 0.05–0.06). They show a maximum external quantum efficiency (EQE_max) of 8.21% and 15.8%, respectively, exhibiting an unprecedented high performance in solution-processed deep-blue TADF-OLEDs. Furthermore, both emitters exhibit excellent device performances (EQE_max = 14.1–15.9%) and color purity in solution-processed doped OLEDs. The current study provides an AIDF emitter design strategy to implement high-efficiency deep-blue OLEDs in the future.

Two simple pure organic molecules (namely p-NN-Br and m-NN-Br) display ultralong organic phosphorescence (UOP), and exhibit dual excited state emission properties. They are found to display distinct responses toward multiple external stimuli including temperature (T), excitation light intensity (I) and pressure (P), and show multicolor emission (orange-yellow to blue (including the white light, CIE = 0.33, 0.34).

Abstract

A simple bromine and cyanogen substituents positional isomeric 9-phenyl-9H-carbazole (PhCz) donor–acceptor system (namely p-NN-Br and m-NN-Br) displays ultralong organic phosphorescence, and exhibits unique dual emission properties (fluorescence and phosphorescence). These molecules are found to display distinct responses toward multiple external stimuli including temperature (T), excitation light intensity (I) and pressure (P), and show multicolor tunable behaviors (including the white light, the Commission Internationale d'Eclairage (CIE) = 0.33, 0.34). The unique stimuli-triggered proportion between singlet and triplet excitons for p-NN-Br and m-NN-Br is demonstrated systematically by investigating the photophysical spectrum, scanning electron microscope (SEM) imaging and X-ray analysis, coupled with theoretical calculations. They reveal that the simultaneous introduction of halogens (Br) and pseudohalogens (CN) to the PhCz skeleton can improve the intermolecular interaction and thermal stability. Single crystal analysis shows that there are many more types of dimers and J-aggregates, thereby stabilizing the excitation of triplet states. Moreover, these isomers have “latent” fingerprint recognition and anti-background interference performance, which is expected to provide a new method for fingerprint identification. All in all, this strategy paves the way to a multifunctional platform for the development of multi-stimuli responsive, multicolor regulation and smart luminescent materials with long-lived emission at room temperature.

Additive-induced synergies of defect passivation and energetic modification in perovskite solar cells are investigated, which boost power conversion efficiency and stability of the devices.

Abstract

Defect passivation via additive and energetic modification via interface engineering are two effective strategies for achieving high-performance perovskite solar cells (PSCs). Here, the synergies of pentafluorophenyl acrylate when used as additive, in which it not only passivates surface defect states but also simultaneously modifies the energetics at the perovskite/Spiro-OMeTAD interface to promote charge transport, are shown. The additive-induced synergy effect significantly suppresses both defect-assisted recombination and interface carrier recombination, resulting in a device efficiency of 22.42% and an open-circuit voltage of 1.193 V with excellent device stability. The two photovoltaic parameters are among the highest values for polycrystalline CsFormamidinium/Methylammonium (FAMA)/FAMA based n-i-p structural PSCs using low-cost silver electrodes reported to date. The findings provide a promising approach by choosing the dual functional additive to enhance efficiency and stability of PSCs.

A synergistic passivation mechanism of a mixed-salt treatment through surface reconstruction engineering is unraveled. This strategy reduces defects and suppresses ion migration of the perovskite interface, leading to enhanced photovoltaic performance meanwhile presenting outstanding operational stability. More generally, the proposed mixed-salt system provides a wider way of designing functional passivation materials, which gets benefits from its synergistic effect.

Abstract

Surface passivation treatment is a widely used strategy to resolve trap-mediated nonradiative recombination toward high-efficiency metal-halide perovskite photovoltaics. However, a lack of passivation with mixture treatment has been investigated, as well as an in-depth understanding of its passivation mechanism. Here, a systematic study on a mixed-salt passivation strategy of formamidinium bromide (FABr) coupled with different F-substituted alkyl lengths of ammonium iodide is demonstrated. It is obtained better device performance with decreasing chain length of the F-substituted alkyl ammonium iodide in the presence of FABr. Moreover, they unraveled a synergistic passivation mechanism of the mixed-salt treatment through surface reconstruction engineering, where FABr dominates the reformation of the perovskite surface via reacting with the excess PbI₂. Meanwhile, ammonium iodide passivates the perovskite grain boundaries both on the surface and top perovskite bulk through penetration. This synergistic passivation engineer results in a high-quality perovskite surface with fewer defects and suppressed ion migration, leading to a champion efficiency of 23.5% with mixed-salt treatment. In addition, the introduction of the moisture resisted F-substituted groups presents a more hydrophobic perovskite surface, thus enabling the decorated devices with excellent long-term stability under a high humid atmosphere as well as operational conditions.

An in-situ hot oxygen cleansing with superior trap passivation method is developed to prepare mixed-halide CsPbTh₃ films during ambient fabrication of solar cells. The results reveal that organic residues are removed and halide vacancies can be effectively decreased by this straightforward technique. The power conversion efficiency is increased significantly from 17.15% to 19.65% with E _loss reduction from 0.57 to 0.48 eV.

Abstract

All-inorganic perovskite CsPbI₃ has attracted extensive attention recently because of its excellent thermal and chemical stability. However, its photovoltaic performance is hindered by large energy losses (E _loss) due to the presence of point defects. In addition, hydroiodic acid (HI) is currently employed as a hydrolysis-derived precursor of intermediate compounds, which often leads to a small amount of organic residue, thus undermining its chemical stability. Herein, an in-situ hot oxygen cleansing with superior passivation (HOCP) for the triple halide-mixed CsPb(I_2.85Br_0.149Cl_0.001) perovskite solar cells (abbreviated as CsPbTh₃) deposited in an ambient atmosphere to reduce the E _loss to as low as 0.48 eV for the power conversion efficiency (PCE) to reach 19.65% is demonstrated. It is found that the hot oxygen treatment effectively removes the organic residues. Meanwhile, it passivates halide vacancies, hence reduces the trap states and nonradiative recombination losses within the perovskite layer. As a result, the PCE is increased significantly from 17.15% to 19.65% under 1 sun illumination with an open-circuit voltage enlarged to 1.23 from 1.14 V, which corresponds to an E _loss reduction from 0.57 to 0.48 eV. Also, the HOCP-treated devices exhibit better long-term stability. This insight should pave a way for decreasing nonradiative charge recombination losses for high-performance inorganic perovskite photoelectronics.

Lycopene, a botanic antioxidant, is introduced to modify the perovskite film for adjusting crystallization through carbon-halogen bonds, and preventing moisture and oxygen erosion. Therefore, the optimized device yields efficiencies of 21.04% under 100 mW cm⁻² and 40.24% at 1000 lux. It also retains almost 90% of the original efficiency value after exposure to wet oxygen ambience for 1000 h.

Abstract

Perovskite (PVSK) photovoltaics have been a promising field in the exploitation of renewable energy due to the fascinating performances of PVSK materials and devices. Although the efficiency is gradually approaching that of traditional solar cells, the stability is still a challenge. Hence, tomato lycopene, a botanic antioxidant, is introduced as a modification layer on the PVSK absorber layer to prevent moisture and oxygen erosion, for enhanced both intrinsic and environmental stabilities. This inserted protection layer can also interact with the PVSK material through carbon-halogen bonds and influence its crystallinity. Therefore, PVSK films are obtained with less defects and better intrinsic stability. The device achieved a champion outdoor efficiency at AM 1.5G more than 21% and its indoor efficiency at 1000 lux can reach 40.24%. In addition, the efficiency can keep almost 90% of the original value after exposure to wet oxygen ambience for 1000 h. The antioxidant gives a unique perspective towards enhancing the stability of solar cells

Novel hole transport material CPDA 1 can be efficiently and inexpensively synthesized from readily available starting materials. The cyclopentadiene acetal core is surrounded by four triarylamine arms in a star-shaped fashion. Excellent optoelectronic, thermal, and transport properties lead to high power conversion efficiencies of 23.1% in perovskite solar cells with respectable long-term stability.

Abstract

Hole transport materials (HTM) are an important component in perovskite solar cells (PSC). Despite a multitude of HTMs developed in recent years, only few of them lead to solar cells with efficiencies over 20%. Therefore, it is still a challenge to develop high-performing HTMs, which have ideal energy levels of the frontier orbitals, are highly efficient in transporting charges, and stabilize the solar cell at the same time. In this work, the development of a structurally novel molecular HTM, CPDA 1, is described which is based on a common cyclopentadiene core and can be efficiently and inexpensively synthesized from readily available starting materials, which is important for future realization of low-cost photovoltaics on larger scale. Due to excellent optoelectronic, thermal, and transport properties, CPDA 1 not only meets the envisioned properties by reaching high efficiencies of 23.1%, which is among the highest reported to date, but also contributes to a respectable long-term stability of the PSCs.

The concept of a ternary-cation two-step sequential deposition method by incorporating cesium acetate (CsAc) into a lead iodide precursor is put forward, which generates cesium lead iodide (CsPbI₃) crystal nuclei. When an organic amine salts solution spin coats the substate, the acetate moves upward and induces perovskite orientational and uniform crystallization achieving fewer defects and higher photovoltaic efficiency.

Abstract

State-of-the-art, high-performance formamidinium-lead-iodide-based (FAPbI₃-based) perovskite photovoltaics are mainly prepared by one-step antisolvent dripping deposition or two-step sequential fabrication methods. Compared with the one-step deposition, the two-step fabricated perovskite films tend to grow columnar perovskite grains vertically which is easier for carrier extraction and transportation. Herein, the concept of formamidinium methylammonium cesium based ternary-cation two-step sequential deposition method is put forward by incorporating cesium acetate (CsAc) into a lead iodide precursor, which generates CsPbI₃ crystal nuclei improving the further perovskite crystallization. When the formamidinium/methylammonium-based organic amine salts solution is spin coated on the PbI₂ substrate, the acetate moves upward and induces perovskite orientational and uniform crystallization, which can go a step further for the vertical columnar grains achieving fewer defects and higher photovoltaic efficiency. The champion outdoor power conversion efficiency of the modified device under AM 1.5G reaches 21.50% and its indoor efficiency at 1000 lux reaches 40.99%. This work paves the way for further exploring ternary-cation two-step sequential deposition methods to prepare high-performance perovskite photovoltaics.

Upscaling efficient and stable perovskite layers is one of the most challenging issues in the commercialization of perovskite solar cells. Here, a lead halide–templated crystallization strategy is developed for printing formamidinium (FA)–cesium (Cs) lead triiodide perovskite films. High-quality large-area films are achieved through controlled nucleation and growth of a lead halide•N-methyl-2-pyrrolidone adduct that can react in situ with embedded FAI/CsI to directly form α-phase perovskite, sidestepping the phase transformation from -phase. A nonencapsulated device with 23% efficiency and excellent long-term thermal stability (at 85°C) in ambient air (~80% efficiency retention after 500 hours) is achieved with further addition of potassium hexafluorophosphate. The slot die–printed minimodules achieve champion efficiencies of 20.42% (certified efficiency 19.3%) and 19.54% with an active area of 17.1 and 65.0 square centimeters, respectively.

This work presents a facile, low-cost, and upscalable process for depositing a mesoporous NiO _x (mp-NiO _x ) layer based on a polymer templating approach by spin-coating. Herein, this templated mp-NiO _x film is employed as a hole-transport layer in inverted perovskite solar cells with an outstanding efficiency larger than 20%. The beneficial effects of this mp-NiO _x layer, such as negligible hysteresis and reduced recombination losses are demonstrated.

Abstract

Despite the outstanding role of mesoscopic structures on the efficiency and stability of perovskite solar cells (PSCs) in the regular (n–i–p) architecture, mesoscopic PSCs in inverted (p–i–n) architecture have rarely been reported. Herein, an efficient and stable mesoscopic NiO _x (mp-NiO _x ) scaffold formed via a simple and low-cost triblock copolymer template-assisted strategy is employed, and this mp-NiO _x film is utilized as a hole transport layer (HTL) in PSCs, for the first time. Promisingly, this approach allows the fabrication of homogenous, crack-free, and robust 150 nm thick mp-NiO _x HTLs through a facile chemical approach. Such a high-quality templated mp-NiO _x structure promotes the growth of the perovskite film yielding better surface coverage and enlarged grains. These desired structural and morphological features effectively translate into improved charge extraction, accelerated charge transportation, and suppressed trap-assisted recombination. Ultimately, a considerable efficiency of 20.2% is achieved with negligible hysteresis which is among the highest efficiencies for mp-NiO _x based inverted PSCs so far. Moreover, mesoscopic devices indicate higher long-term stability under ambient conditions compared to planar devices. Overall, these results may set new benchmarks in terms of performance for mesoscopic inverted PSCs employing templated mp-NiO _x films as highly efficient, stable, and easy fabricated HTLs.

Publication date: October 2021

Source: Nano Energy, Volume 88

Author(s): Yulan Huang, Tanghao Liu, Dongyang Li, Dandan Zhao, Abbas Amini, Chun Cheng, Guichuan Xing

Publication date: September 2021

Source: Nano Energy, Volume 87

Author(s): Huyen T. Pham, Yanting Yin, Gunther Andersson, Klaus J. Weber, The Duong, Jennifer Wong-Leung

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.