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.

Au Nanocluster Assisted Microstructural Reconstruction for Buried Interface Healing for Enhanced Perovskite Solar Cell Performance

The heterogeneity of perovskite film crystallization along the vertical direction leads to voids and traps at the buried interfaces, hampering both efficiency and stability of perovskite solar cells. Here, bovine serum albumin-functionalized Au nanoclusters (ABSA), combined with heavy gravity, high surface charge density, and strong interactions with the electron transport layer, are designed to reconstruct the buried interfaces for not only high-quality crystallization, but also improved carrier transfer. The ABSA macromolecules with amine function groups and larger surface charge density interact with the perovskite to improve the crystallinity, and gradually migrate towards the buried interface, healing the defective voids, hence suppressing surface recombination velocity from 3075 to 452 cm s-1 . The healed buried interface and the higher surface potential of ABSA-modified TiO2 lead to improved carrier extraction at the interface. The resulting solar cell attains a power conversion efficiency of 25.0% with negligible hysteresis and remarkable stability, maintaining 92.9% of their initial efficiency after 3200 h of exposure to the ambient atmosphere, they also exhibit better continuous irradiation stability compared to control devices. These findings provide a new metal-protein complex to eliminate the deleterious voids and defects at the buried interface for improved photovoltaic performance and stability.

Crystallization Regulation by Self-Assembling Liquid Crystal Template Enables Efficient and Stable Perovskite Solar Cells

It is found that the disordered growth of bottom perovskite film deteriorates the buried interface of perovskite solar cells (PSCs), so developing a new material to modify the buried interface for regulating the crystal growth and defect passivation is an effective approach for improving the photovoltaic performance of PSCs. Here, we developed a new ionic liquid crystal (ILC, 1-Dodecyl-3-methylimidazolium tetrafluoroborate) as both crystal regulator and defect passivator to modify the buried interface of PSCs. The high lattice matching between this ILC and perovskite promotes preferential growth of perovskite film along [001] direction, while the oriented ILC with mesomorphic phase has a strong chemical interaction with perovskite to passivate the interface defect, as a result, the modified buried interface exhibits suppressed defects, improved band alignment, reduced nonradiative recombination losses, and enhanced charge extraction. The ILC-modified PSC delivers a power conversion efficiency of 24.92 % and maintains 94 % of the original value after storage in ambient for 3000 h.

Origin and Mechanism of Piezoelectric and Photovoltaic Effects in (111) Polar Orientated NiO Films

Based on the current piezoelectric theory, NiO with the centrosymmetric structure is not piezoelectric. However, herein, this study shows the first observation of piezoelectric generation, rectifyingand bulk photovoltaic behaviors in NiO films with [111] orientation and the change in NiO crystal structure in piezoelectric process. The piezoelectric generation, rectifying, and bulk photovoltaic performances are enhanced by increasing (111) orientation, and attenuated and eliminated by applying a persistent stress on the NiO film. The NiO [111] is polar direction, and thus a spontaneous electric field (ES ) is in the NiO film with [111] orientation. The existence of Es in (111) oriented NiO film is found to be the physical basis of the piezoelectric generators and photovoltaic and rectifying effects. Thus, NiO piezoelectric, rectifying, and bulk photovoltaic mechanism are presented at the atomic level. The mechanism may rewrite the current piezoelectric theory, and establish a unified theory of polar structure with wide implications. The polar-orientated films can be used to fabricate piezoelectric generators and other optoelectronic devices with high performances.

Halide Perovskite: A Promising Candidate for Next-Generation X-Ray Detectors

In the past decade, metal halide perovskite (HP) has become a superstar semiconductor material due to its great application potential in the photovoltaic and photoelectric fields. In fact, HP initially attracted worldwide attention because of its excellent photovoltaic efficiency. However, HP and its derivatives also show great promise in X-ray detection due to their strong X-ray absorption, high bulk resistivity, suitable optical bandgap, and compatibility with integrated circuits. In this review, the basic working principles and modes of both the direct-type and the indirect-type X-ray detectors are first summarized before discussing the applicability of HP for these two types of detection based on the pros and cons of different perovskites. Furthermore, the authors expand their view to different preparation methods developed for HP including single crystals and polycrystalline materials. Upon systematically analyzing their potential for X-ray detection and photoelectronic characteristics on the basis of different structures and dimensions (0D, 2D, and 3D), recent progress of HPs (mainly polycrystalline) applied to flexible X-ray detection are reviewed, and their practicability and feasibility are discussed. Finally, by reviewing the current research on HP-based X-ray detection, the challenges in this field are identified, and the main directions and prospects of future research are suggested.

Tapered Coaxial Arrays for Photon- and Plasmon-Enhanced Light Harvesting in Perovskite Solar Cells: A Theoretical Investigation Using the Finite Element Method

Although there have been reports of separate studies of photon-enhanced and plasmon-enhanced light harvesting to improve perovskite solar cell (PSC) efficiency, there are none that have achieved simultaneous enhancement in both photonic and plasmonic effects in PSCs. In this work, we designed a layer of tapered coaxial humps (TCHs) to harvest both in PSCs. The light absorption behavior of the textured perovskite layer in PSCs was systematically investigated through the finite element method (FEM). The calculation results show that the TCH-textured perovskite layer absorbs 67.6 % of visible light under AM 1.5G solar irradiation, a 21.8 % increase relative to the planar reference cell without TCHs. Using this design, a perovskite thickness of only 106 nm is needed to realize the full light absorption that normally requires 300-nm-thick perovskite without TCHs. To reveal the mechanism of light absorption enhancement, the specific field distributions were studied. We demonstrated that different photonic modes and plasmonic modes collectively result in remarkable light absorption enhancement in the 500-800 nm wavelength range. The textured PSCs reported herein provide an effective method to decrease Pb-based perovskite consumption and realize angle-insensitive and ultrathin PSCs.