Atomic-Scale Imaging and Nano-Scale Mapping of Cubic α-CsPbI3 Perovskite Nanocrystals for Inverted Perovskite Solar Cells

Scaling Up Purcell-Enhanced Self-Assembled Nanoplasmonic Perovskite Scintillators into the Bulk Regime

Scintillators convert high-energy radiation into detectable photons and play a crucial role in medical imaging and security applications. The enhancement of scintillator performance through nanophotonics and nanoplasmonics, specifically using the Purcell effect, has shown promise but has so far been limited to ultrathin scintillator films because of the localized nature of this effect. This study introduces a method to expand the application of nanoplasmonic scintillators to the bulk regime. By integrating 100-nm-sized plasmonic spheroid and cuboid nanoparticles with perovskite scintillator nanocrystals, nanoplasmonic scintillators are enabled to function effectively within bulk-scale devices. Power and decay rate enhancements of up to (3.20 ± 0.20) and (4.20 ± 0.31) folds are experimentally demonstrated for plasmonic spheroid and cuboid nanoparticles, respectively, in a 5-mm thick CsPbBr3 nanocrystal-polymer scintillator at RT. Theoretical modeling also predicts similar enhancements of up to (2.26 ± 0.31) and (3.02 ± 0.69) folds for the same nanoparticle shapes and dimensions. Moreover, a (2.07 ± 0.39) fold increase in light yield under 241Am γ-excitation is demonstrated. These findings provide a viable pathway for utilizing nanoplasmonics to enhance bulk scintillator devices, advancing radiation detection technology.

Superior photoconversion efficiency of nanocrystal sensitized solar cells based on all-inorganic CsPbX3 (X = Br, I) perovskites

Nanocrystal-sensitized solar cells have emerged as potential alternatives to traditional photovoltaic technology due to their unique light absorption and emission characteristics and size-dependent bandgap. In this work, we report the successful synthesis of cubic-phase CsPbI3 and CsPbBr3 nanocrystals for their use as photosensitizers in solar cells, referred to as perovskite nanocrystal-sensitized solar cells (PNCSSCs). Among the two systems, CsPbI3 is found to be superior for PNCSSCs because of its high absorption efficiency, lower bandgap, and higher photoluminescence yield, as compared to CsPbBr3. Our study examines the structural, compositional, optical, and electrical properties of these perovskite nanocrystals, focusing on their contributions to photoconversion efficiency. CsPbBr3 nanocrystals exhibit a band gap of ∼2.4 eV along with defect states-induced short carrier lifetime of around 18 ns. In contrast, CsPbI3 demonstrates a band gap of ∼1.8 eV closer to the peak of the solar spectrum with a much longer carrier lifetime of ∼130 ns, which facilitates better separation and collection of photogenerated charge carriers. Consequently, CsPbI3 nanocrystal-sensitized solar cells fabricated with mesoporous TiO2 reveal a photoconversion efficiency of ∼12.5%, as compared to 3.8% for CsPbBr3 nanocrystal solar cells. To the best of our knowledge, this is the highest reported photoconversion efficiency in solution-processed perovskite nanocrystal-sensitized solar cells.

Revival of Degraded CsPbI3 Nanocrystals by Diselenide Ligand and Nanocrystal Self-Assembly on Nanofibrilar Ligand Template

Among the lead halide perovskite (LHP) family, CsPbI3 is known to be significantly vulnerable to moisture, which hinders its use in real device applications. It is reported that chalcogen-based ligands can better stabilize CsPbI3 and revive nanocrystals (NCs). Here, diphenyl diselenide (DPhDSe) ligand is used to revive the degraded CsPbI3 NCs through a post-synthetic treatment of adding a small amount of DPhDSe in the degraded NC dispersion. DPhDSe in the dispersion formed nanofibrillar crystals at a low temperature through the π-π stacking of the phenyl ring. The nanofibrils played as a template on which the NCs self-assembled and they are attached side-by-side to form microfibers. The microfiber powder containing the NCs is optically stable at ambient conditions and morphologically self-healable by mild thermal annealing due to the dynamic Se─Se bond. The mechanism of the structural changes, optical transitions, and chemical changes has been systematically characterized through electron microscopy, diffraction, spectroscopy, and elemental analysis.

Phase stabilization of cesium lead iodide perovskites for use in efficient optoelectronic devices

All-inorganic lead halide perovskites (LHPs) and their use in optoelectronic devices have been widely explored because they are more thermally stable than their hybrid organic‒inorganic counterparts. However, the active perovskite phases of some inorganic LHPs are metastable at room temperature due to the critical structural tolerance factor. For example, black phase CsPbI3 is easily transformed back to the nonperovskite yellow phase at ambient temperature. Much attention has been paid to improving the phase stabilities of inorganic LHPs, especially those with high solar cell efficiencies. Herein, we discussed the origin of phase stability for CsPbI3 and the strategies used to stabilize the cubic (α) phase. We also assessed the CsPbI3 black β/γ phases that are relatively stable at nearly room temperature. Furthermore, we determined the relationship between phase stabilization and defect passivation and reviewed the growing trend in solar cell efficiency based on black phase CsPbI3. Finally, we provide perspectives for future research related to the quest for optimum device efficiency and green energy.

Advancements in Perovskite Nanocrystal Stability Enhancement: A Comprehensive Review

Over the past decade, perovskite technology has been increasingly applied in solar cells, nanocrystals, and light-emitting diodes (LEDs). Perovskite nanocrystals (PNCs) have attracted significant interest in the field of optoelectronics owing to their exceptional optoelectronic properties. Compared with other common nanocrystal materials, perovskite nanomaterials have many advantages, such as high absorption coefficients and tunable bandgaps. Owing to their rapid development in efficiency and huge potential, perovskite materials are considered the future of photovoltaics. Among different types of PNCs, CsPbBr₃ perovskites exhibit several advantages. CsPbBr₃ nanocrystals offer a combination of enhanced stability, high photoluminescence quantum yield, narrow emission bandwidth, tunable bandgap, and ease of synthesis, which distinguish them from other PNCs, and make them suitable for various applications in optoelectronics and photonics. However, PNCs also have some shortcomings: they are highly susceptible to degradation caused by environmental factors, such as moisture, oxygen, and light, which limits their long-term performance and hinders their practical applications. Recently, researchers have focused on improving the stability of PNCs, starting with the synthesis of nanocrystals and optimizing (i) the external encapsulation of crystals, (ii) ligands used for the separation and purification of nanocrystals, and (iii) initial synthesis methods or material doping. In this review, we discuss in detail the factors leading to instability in PNCs, introduce stability enhancement methods for mainly inorganic PNCs mentioned above, and provide a summary of these approaches.

Tiny spots to light the future: advances in synthesis, properties, and application of perovskite nanocrystals in solar cells

Perovskites are in the hotspot of material science and technology. Outstanding properties have been discovered, fundamental mechanisms of defect formation and degradation elucidated, and applications in a wide variety of optoelectronic devices demonstrated. Advances through adjusting the bulk-perovskite composition, as well as the integration of layered and nanostructured perovskites in the devices, allowed improvement in performance and stability. Recently, efforts have been devoted to investigating the effects of quantum confinement in perovskite nanocrystals (PNCs) aiming to fabricate optoelectronic devices based solely on these nanoparticles. In general, the applications are focused on light-emitting diodes, especially because of the high color purity and high fluorescence quantum yield obtained in PNCs. Likewise, they present important characteristics featured for photovoltaic applications, highlighting the possibility of stabilizing photoactive phases that are unstable in their bulk analog, the fine control of the bandgap through size change, low defect density, and compatibility with large-scale deposition techniques. Despite the progress made in the last years towards the improvement in the performance and stability of PNCs-based solar cells, their efficiency is still much lower than that obtained with bulk perovskite, and discussions about upscaling of this technology are scarce. In light of this, we address in this review recent routes towards efficiency improvement and the up-scaling of PNC solar cells, emphasizing synthesis management and strategies for solar cell fabrication.

Hybrid Block Copolymer/Perovskite Heterointerfaces for Efficient Solar Cells

Solution processable semiconductors like organics and emerging lead halide perovskites (LHPs) are ideal candidates for photovoltaics combining high performance and flexibility with reduced manufacturing cost. Moreover, the study of hybrid semiconductors would lead to advanced structures and deep understanding that will propel this field even further. Herein, a novel device architecture involving block copolymer/perovskite hybrid bulk heterointerfaces is investigated, such a modification could enhance light absorption, create an energy level cascade, and provides a thin hydrophobic layer, thus enabling enhanced carrier generation, promoting energy transfer and preventing moisture invasion, respectively. The resulting hybrid block copolymer/perovskite solar cell exhibits a champion efficiency of 24.07% for 0.0725 cm² -sized devices and 21.44% for 1 cm² -sized devices, respectively, together with enhanced stability, which is among the highest reports of organic/perovskite hybrid devices. More importantly, this approach has been effectively extended to other LHPs with different chemical compositions like MAPbI₃ and CsPbI₃ , which may shed light on the design of highly efficient block copolymer/perovskite hybrid materials and architectures that would overcome current limitations for realistic application exploration.

Low-Temperature-Processed Monolayer Inverse Opal SnO2 Scaffold for Efficient Perovskite Solar Cells

Organic-inorganic halide perovskite solar cells (PSCs) have attracted tremendous attention in the photovoltaic field due to their excellent optical properties and simple fabrication process. However, the recombination of photogenerated electron-hole pairs at the interface severely affects the power conversion efficiency (PCE) of the PSCs. Herein, a monolayer of inverse opal SnO₂ (IO-SnO₂ ) is synthesized via a template-assisted method and used as a scaffold for perovskite layer (PSK). The porous IO-SnO₂ scaffold increases the contact area and shortens the transport distance between the electron transport layer (ETL) and PSK. Ultraviolet photoelectron spectroscopy and Kelvin probe force microscopy results indicate that the built-in electric field is enhanced with IO-SnO₂ scaffold, strengthening the driving force for charge separation. Femtosecond transient absorption spectroscopy measurements reveal that the IO-SnO₂ scaffold facilitates interfacial electron transfer from PSK to ETL. Based on the above superiorities, the IO-SnO₂ -based PSCs exhibit boosted PCE and device stability compared with the pristine PSCs. This work provides insights into the development of novel scaffold layers for high-performance PSCs.