The stabilization of black-phase formamidinium lead iodide (α-FAPbI
) perovskite under various environmental conditions is considered necessary for solar cells. However, challenges remain regarding ...the temperature sensitivity of α-FAPbI
and the requirements for strict humidity control in its processing. Here we report the synthesis of stable α-FAPbI
, regardless of humidity and temperature, based on a vertically aligned lead iodide thin film grown from an ionic liquid, methylamine formate. The vertically grown structure has numerous nanometer-scale ion channels that facilitate the permeation of formamidinium iodide into the lead iodide thin films for fast and robust transformation to α-FAPbI
A solar cell with a power-conversion efficiency of 24.1% was achieved. The unencapsulated cells retain 80 and 90% of their initial efficiencies for 500 hours at 85°C and continuous light stress, respectively.
Tin halide perovskites attract incremental attention to deliver lead‐free perovskite solar cells. Nevertheless, disordered crystal growth and low defect formation energy, related to Sn(II) oxidation ...to Sn(IV), limit the efficiency and stability of solar cells. Engineering the processing from perovskite precursor solution preparation to film crystallization is crucial to tackle these issues and enable the full photovoltaic potential of tin halide perovskites. Herein, the ionic liquid n‐butylammonium acetate (BAAc) is used to tune the tin coordination with specific O…Sn chelating bonds and NH…X hydrogen bonds. The coordination between BAAc and tin enables modulation of the crystallization of the perovskite in a thin film. The resulting BAAc‐containing perovskite films are more compact and have a preferential crystal orientation. Moreover, a lower amount of Sn(IV) and related chemical defects are found for the BAAc‐containing perovskites. Tin halide perovskite solar cells processed with BAAc show a power conversion efficiency of over 10%. This value is retained after storing the devices for over 1000 h in nitrogen. This work paves the way toward a more controlled tin‐based perovskite crystallization for stable and efficient lead‐free perovskite photovoltaics.
The synergistic strategy of tuning the solution coordination and crystallization process by introducing ionic liquid is implemented to successfully fabricate pinhole‐free tin perovskite films with preferential crystal orientation, which possess improved oxidation repellency for Sn(II) and enhanced hydrophobicity. As a result, the stabilization of high‐efficiency lead‐free tin halide perovskite solar cells is achieved.
Flexible perovskite solar cells (FPSCs) represent a promising technology in the development of next‐generation photovoltaic and optoelectronic devices. SnO2 electron transport layers (ETL) typically ...undergo significant cracking during the bending process of FPSCs, which can significantly compromise their charge transport properties. Herein, the semi‐planar non‐fullerene acceptor molecule Y6 (BT‐core‐based fused‐unit dithienothiophen 3,2‐b‐pyrrolobenzothiadiazole derivative) is introduced as the buffer layer for SnO2‐based FPSCs. It is found that the Y6 buffer layer can enhance the ability of charge extraction and bending stability for SnO2 ETL. Moreover, the internal stress of perovskite films is also reduced. As a result, SnO2/Y6‐based FPSCs achieved a power conversion efficiency (PCE) of 20.09% and retained over 80% of their initial efficiency after 1000 bending cycles at a curvature radius of 8 mm, while SnO2‐based devices only retain 60% of their initial PCE (18.60%) upon the same bending cycles. In addition, the interfacial charge extraction is also effectively improved in conjunction with reduced defect density upon incorporation of Y6 on the SnO2 ETL, as revealed by femtosecond transient absorption (Fs‐TA) measurements.
Y6 passivation layer can enhance SnO2 ETL durability during bending processes. The SnO2/Y6‐based FPSCs achieve a PCEof 20.09% and retain over 80% of their initial efficiency after 1000 bending cycles at a curvature radius of 8 mm, while SnO2‐based devices only retain 60% of their initial PCE (18.60%) upon the same bending cycles.
The addition of methylammonium chloride (MACl) significantly improves the performance and stability of perovskite fabricated by two-step processes. However, its role in crystallization dynamics has ...not been thoroughly studied. In this work, a comparison study is carried out using different additions of MACl to investigate the impact of the perovskite crystallization dynamics. In situ grazing incidence wide-angle X-ray scattering (GIWAXS) observations during the annealing process of perovskite revealed that the amount of MACl significantly influences the crystallinity and orientation of the perovskite. Increasing the MACl addition enhances the crystallinity of the perovskite in the wet film‘s intermediate phase and strengthens the out-of-plane orientation of the FAPbI3 perovskite α-phase (001) planes during annealing. Moreover, it was found that both excessive and insufficient amounts of MACl introduce defects into the perovskite, which are detrimental to device performance. In contrast, an optimal ratio of MACl-9 mg leads to the formation of uniform and large-grained FAPbI3 perovskite films, with the longest carrier lifetimes (163.7 ns) compared to MACl-5 mg (68.4 ns) and MACl- 13 mg (120.1 ns). As a result, the fabricated MACl-9 mg-based solar cell achieved the highest efficiency (22.63%), which is higher than those of MACl-5 mg (21.47%) and MACl-13 mg (20.07%).
Metal halide perovskite materials have demonstrated significant potential in various optoelectronic applications, such as photovoltaics, light emitting diodes, photodetectors, and lasers. However, ...the stability issues of perovskite materials continue to impede their widespread use. Many studies have attempted to understand the complex degradation mechanism and dynamics of these materials. Among them, in situ and/or operando approaches have provided remarkable insights into the degradation process by enabling precise control of degradation parameters and real-time monitoring. In this review, we focus on these studies utilizing in situ and operando approaches and demonstrate how these techniques have contributed to reveal degradation details, including structural, compositional, morphological, and other changes. We explore why these two approaches are necessary in the study of perovskite degradation and how they can be achieved by upgrading the corresponding ex situ techniques. With recent stability improvements of halide perovskite using various methods (compositional engineering, surface engineering, and structural engineering), the degradation of halide perovskite materials is greatly retarded. However, these improvements may turn into new challenges during the investigation into the retarded degradation process. Therefore, we also highlight the importance of enhancing the sensitivity and probing range of current in situ and operando approaches to address this issue. Finally, we identify the challenges and future directions of in situ and operando approaches in the stability research of halide perovskites. We believe that the advancement of in situ and operando techniques will be crucial in supporting the journey toward enhanced perovskite stability.
Inkjet-printed quantum dot light-emitting diodes (QLEDs) are emerging as a promising technology for next-generation displays. However, the progress in fabricating QLEDs using inkjet printing ...technique has been slower compared to spin-coated devices, particularly in terms of efficiency and stability. The key to achieving high performance QLEDs lies in creating a highly ordered and uniform inkjet-printed quantum dot (QD) thin film. In this study, we present a highly effective strategy to significantly improve the quality of inkjet-printed CdZnSe/CdZnS/ZnS QD thin films through a pressure-assisted thermal annealing (PTA) approach. Benefiting from this PTA process, a high quality QD thin film with ordered packing, low surface roughness, high photoluminescence and excellent electrical property is obtained. The mechanism behind the PTA process and its profound impact on device performance have been thoroughly investigated and understood. Consequently, a record high external quantum efficiency (EQE) of 23.08% with an impressive operational lifetime (T50) of up to 343,342 h@100 cd m−2, and a record EQE of 22.43% with T50 exceeding to 1,500,463 h@100 cd m−2 are achieved in inkjet-printed red and green CdZnSe-based QLEDs, respectively. This work highlights the PTA process as an important approach to realize highly efficient and stable inkjet-printed QLEDs, thus advancing QLED technology to practical applications.
Display omitted
•A pressure-assisted thermal annealing (PTA) strategy is proposed firstly to control the ordered packing of inkjet-printed QD thin films.•The mechanism of PTA process and its thin-film quality and QLED performance influences are systematically investigated and understood.•A record EQE of 23.08% with an impressive operational lifetime is achieved in our inkjet-printed red QLED.
Quasi‐2D metal halide perovskite light emitting diodes (PeLEDs) have attracted a lot of attentions in recent years, while their potential applications in displays and lighting are limited by the ...device stability. Although defect passivation in PeLEDs is an effective method to ameliorate the unstable problem, the underlying mechanisms need to be further explored. Herein, organic spacer cations with different charge distributions and formation energies in quasi‐2D CsPbBr3 perovskites are utilized to unravel the defect passivation mechanisms, including phenylmethanamine, 2‐phenylethanamine bromide, and 4‐phenylbutylammonium. The experimental findings and density functional theory calculation reveal that the defect passivation occurs by the electrostatic interaction between defective PbBr64− octahedrons and proper organic spacer cations during the annealing process, particularly at the grain boundaries. The thermal stability of the perovskite films and device performance are improved after the effective defect passivation process. The exploration of the defect passivation process in perovskites will be beneficial to the development of high‐performance PeLEDs.
The defect passivation mechanisms of quasi‐2D perovskites induced by organic spacer cations with different charge distributions and formation energies are unveiled by in situ characterizations and theoretical calculations. The crystallization process of perovskites with suppressed defect states can be affected due to electrostatic interaction between defective PbBr64− octahedrons and organic spacer cations at the grain boundaries.
Highlights
High-quality large-area perovskite films are prepared using a solid–liquid two-step film formation method combined with CsBr modification for the buried interface and Urea additive for ...perovskite crystallization.
The inverted perovskite solar modules’ performance is enhanced to 20.56% in 61.56 cm
2
with improved stability.
A considerable efficiency gap exists between large-area perovskite solar modules and small-area perovskite solar cells. The control of forming uniform and large-area film and perovskite crystallization is still the main obstacle restricting the efficiency of PSMs. In this work, we adopted a solid–liquid two-step film formation technique, which involved the evaporation of a lead iodide film and blade coating of an organic ammonium halide solution to prepare perovskite films. This method possesses the advantages of integrating vapor deposition and solution methods, which could apply to substrates with different roughness and avoid using toxic solvents to achieve a more uniform, large-area perovskite film. Furthermore, modification of the NiO
x
/perovskite buried interface and introduction of Urea additives were utilized to reduce interface recombination and regulate perovskite crystallization. As a result, a large-area perovskite film possessing larger grains, fewer pinholes, and reduced defects could be achieved. The inverted PSM with an active area of 61.56 cm
2
(10 × 10 cm
2
substrate) achieved a champion power conversion efficiency of 20.56% and significantly improved stability. This method suggests an innovative approach to resolving the uniformity issue associated with large-area film fabrication.
PDF
