"One-Click Restart" Recycling of Metal-Free Perovskite X-Ray Detectors

Halide perovskites have shown great potential in X-ray detection due to outstanding optoelectronic properties. However, finding a cost-effective and environmentally sustainable method for handling end-of-life devices has remained challenging. Here, a "One-Click Restart" eco-friendly recycling strategy is introduced for end-of-life perovskite X-ray detectors. This method, utilizing water, allows for the recapture and reuse of both perovskite and conductor materials. The process is straightforward and environmentally friendly, eliminating the need for further chemical treatment, purification, additional additives or catalysts, and complex equipment. A sustainable device cycle is developed by reconstructing flexible perovskite membranes for wearable electronics from recycled materials. Large-scale, flexible membranes made from metal-free perovskite DABCO-N2H5-I3 (DABCO = N-N'-diazabicyclo[2.2.2]octonium) achieve remarkably impressive average sensitivity of 6204 ± 268 µC Gyair -1 cm-2 and a low detection limit of 102.3 nGyair s-1, which makes highly effective for X-ray imaging. The sensitivity of recycled flexible devices not only matches that of single-crystal devices made with fresh materials but also ranks as the highest among all metal-free perovskite X-ray detectors. "One-Click Restart" applies to scalable flexible devices derived from aged single-crystal counterparts, offering significant cost, time, and energy savings compared to their single-crystal equivalents. Such advantages significantly boost future market competitiveness.

Lead-Free Perovskite Single Crystal Linear Array Detector for High-Resolution X-Ray Imaging

0D Bi-based 329-type halide perovskite is demonstrated as a promising semiconductor for X-ray detection due to its strong X-ray absorption, superior stability, availability of large single crystals (SCs) and solution processibility at low temperature. However, its low mobility-lifetime product (µτ) limits its further improvement in detection sensitivity. Based on the first-principles calculations, this work designs a new 2D Bi-based 329-type halide perovskite using a mixed-halide-induced structural dimension regulation strategy. By using a continuous supply of a precursor solution, this work successfully grows inch-sized high-quality SCs. These SCs exhibit large µτ product, high resistivity, and low ion migration. The detectors fabricated using the SCs show X-ray detection sensitivity as high as 24,509 µC Gyair -1 cm-2, short response time of 315 µs, low detection limit of 4.3 nGy s-1, and superior stability. These properties are the best among all lead-free perovskite detectors and are comparable to those of the best lead-based perovskite detectors. The linear array detector assembled on the SCs for the first time also shows a high spatial resolution of 10.6 lp mm-1 during X-ray imaging. The high performance combined with superior stability of these new 329-type lead-free halide perovskite SCs is expected to promote a new generation of X-ray detection technologies.

In Situ Synthesized Low-Dimensional Perovskite for >25% Efficiency Stable MA-Free Perovskite Solar Cells

Developing an additive to effectively regulate the perovskite crystallization kinetics for the optimized optoelectronic properties of perovskite film plays a vital role in obtaining high efficiency and stable perovskite solar cells (PSCs). Herein, a new additive is designed and directly synthesized in perovskite precursor solution by utilizing an addition reaction between but-3-yn-1-amine hydrochloride (BAH) and formamidinium iodide. It is found that its product may control the intermediate precursor phase for regulating perovskite nucleation, leading to advantageous 2D perovskite to induce growth of perovskite along the preferred [001] orientation with not only released lattice strain but also strong interaction with perovskite to passivate its surface defects. By taking advantage of the above synergistic effects, the optimized PSC delivers an efficiency of 25.19% and a high open-circuit voltage (VOC) of 1.22 V. Additionally, the devices demonstrate good stability, remaining over 90% of their initial efficiencies under ambient atmosphere conditions for 60 days, high temperature of 85 °C for 200 h, or maximum power point tracking for 500 h.

Crystallization Control Based on the Regulation of Solvent-Perovskite Coordination for High-Performance Ambient Printable FAPbI3 Perovskite Solar Cells

The critical requirement for ambient-printed formamidinium lead iodide (FAPbI3 ) lies in the control of nucleation-growth kinetics and defect formation behavior, which are extensively influenced by interactions between the solvent and perovskite. Here, a strategy is developed that combines a cosolvent and an additive to efficiently tailor the coordination between the solvent and perovskite. Through in situ characterizations, the direct crystallization from the sol-gel phase to α-FAPbI3 is illustrated. When the solvent exhibits strong interactions with the perovskite, the sol-gel phases cannot effectively transform into α-FAPbI3 , resulting in a lower nucleation rate and confined crystal growth directions. Consequently, it becomes challenging to fabricate high-quality void-free perovskite films. Conversely, weaker solvent-perovskite coordination promotes direct crystallization from sol-gel phases to α-FAPbI3 . This process exhibits more balanced nucleation-growth kinetics and restrains the formation of defects and microstrains in situ. This strategy leads to improved structural and optoelectronic properties within the FAPbI3 films, characterized by more compact grain stacking, smoother surface morphology, released lattice strain, and fewer defects. The ambient-printed FAPbI3 perovskite solar cells fabricated using this strategy exhibit a remarkable power conversion efficiency of 24%, with significantly reduced efficiency deviation and negligible decreases in the stabilized output.

Heterointerface Design of Perovskite Single Crystals for High-Performance X-Ray Imaging

Metal halide perovskite single crystals (MHP-SCs) are known for their facile fabrication into large sizes using inexpensive solution methods. Owing to their combination of large mobility-lifetime products and strong X-ray absorption, they are considered promising materials for efficient X-ray detection. However, they suffer from large dark currents and severe ion migration, which limit their sensitivity and stability in critical X-ray detection applications. Herein, a heterointerface design is proposed to reduce both the dark current and ion migration by forming a heterojunction. In addition, the carrier transport performance is significantly improved using heterointerface engineering by designing a gradient band structure in the SCs. The SC heterojunction detectors exhibit a high sensitivity of 3.98 × 105 µC Gyair -1 cm-2 with a low detection limit of 12.2 nGyair s-1 and a high spatial resolution of 10.2 lp mm-1 during imaging. These values are among the highest reported for state-of-the-art MHP X-ray detectors. Moreover, the detectors show excellent stability under continuous X-ray irradiation and maintainclear X-ray imaging after 240 d. This study provides novel insights into the design and fabrication of X-ray detectors with high detection efficiency and stability, which are beneficial for developing inexpensive, high-resolution X-ray imaging equipment.

In Situ Self-Elimination of Defects via Controlled Perovskite Crystallization Dynamics for High-Performance Solar Cells

Understanding and controlling crystallization is crucial for high-quality perovskite films and efficient solar cells. Herein, the issue of defects in formamidinium lead iodide (FAPbI3 ) formation is addressed, focusing on the role of intermediates. A comprehensive picture of structural and carrier evolution during crystallization is demonstrated using in situ grazing-incidence wide-angle X-ray scattering, ultraviolet-visible spectroscopy and photoluminescence spectroscopy. Three crystallization stages are identified: precursors to the δ-FAPbI3 intermediate, then to α-FAPbI3 , where defects spontaneously emerge. A hydrogen-sulfate-based ionic liquid additive is found to enable the phase-conversion pathway of precursors → solvated intermediates → α-FAPbI3 , during which the spontaneous generation of δ-FAPbI3 can be effectively circumvented. This additive extends the initial growth kinetics and facilitates solvent-FA+ ion exchange, which results in the self-elimination of defects during crystallization. Therefore, the improved crystallization dynamics lead to larger grain sizes and fewer defects within thin films. Ultimately, the improved perovskite crystallization dynamics enable high-performance solar cells, achieving impressive efficiencies of 25.14% at 300 K and 26.12% at 240 K. This breakthrough might open up a new era of application for the emerging perovskite photovoltaic technology to low-temperature environments such as near-space and polar regions.

Surface modulation for highly efficient and stable perovskite solar cells

Defects formed by halide ion escape and wettability of the perovskite absorber are essential limiting factors in achieving high performance of perovskite solar cells (PSCs). Herein, a series of ionic organic modulators are designed to contain halide anions to prevent defect formation and improve the surface tension of the perovskite absorber. It was found that the surface modulator containing Br anions is the most effective one due to its capability in bonding with the undercoordinated Pb2+ ions to reduce charge recombination. Moreover, this surface modulator effectively creates a suitable energy level between the perovskite and hole transport layer to promote carrier transfer. In addition, the surface modulator forms a chemisorbed capping layer on the perovskite surface to improve its hydrophobicity. As a result, the efficiency of PSCs based on surface modulators containing Br anion enhances to 23.32% from 21.08% of the control device. The efficiency of unencapsulated PSCs with a surface modulator retains 75.42% of its initial value under about 35% humidity stored in the air for 28 days, while the control device only maintained 44.49% of its initial efficiency. The excellent stability originates from the hydrophobic perovskite surface after capping the surface modulator.