[en] Planar heterojunction perovskite solar cells have emerged as competitive photovoltaic technology, where charge transport materials play a crucial role. Here, we successfully demonstrate a systematic approach to investigate the doping effect on SnO₂ electron transport material, based on the introduction of metal chloride with different valance states. A thorough characterization by x-ray diffraction, x-ray photoelectron spectroscopy, space charge limited current, transmittance, time-resolved photoluminescence and electrochemical impedance spectroscopy measurements was performed to gain an understanding of the SnO₂-based materials and devices. It was revealed that proper doping in the electron transport layer can benefit V _OC and/or J _SC in the devices, due to improved crystallinity, conductivity and transmittance, along with faster interface transfer. Further analysis indicates that certain doping elements are increasingly beneficial to cell performance, which follows the sequence of Li, Mg and Sb. We present here the overall performance improvement from the original efficiency of 15.48% to an elevated one as 17.07% with our Sb-doped SnO₂ cell. The enhancement in conductivity also confirms that p-type doping for SnO₂ in this case can still be favorable. Furthermore, the entire device was fabricated via a solution process with the processing temperature below 200 °C, suggesting a promising way toward the further development of low-cost perovskite solar cells and commercial manufacturing. (paper)

[en] Here, we introduced acetamidine (C₂H₃N₂H₃, Aa)-based salt as an additive in the fabrication of perovskite (CH₃NH₃PbI₃) layer for perovskite solar cells. It was found that as an amidine-based salt, this additive successfully enhanced the crystallinity of CH₃NH₃PbI₃ and helped to form smooth and uniform films with comparable grain size and full coverage. Besides, perovskite film with additive showed a much longer carrier lifetime and an obviously enhanced open-circuit voltage in the corresponding devices, indicating that the acetamidine-based salt can reduce the carrier recombination in both the film and device. We further demonstrate a promising perovskite device based on acetamidine salt by using a configuration of ITO/TiO₂/Perovskite/Spiro-OMeTAD/Au under < 150 °C fabrication condition. A power conversion efficiency (PCE) of 16.54% was achieved, which is much higher than the control device without acetamidine salt. These results present a simple method for film quality optimization of perovskite to further improve photovoltaic performances of perovskite solar cells, which may also benefit the exploration of A cation in perovskite materials. (paper)

[en] The transcription factor nuclear factor E2-related factor 2 (Nrf2) is known to control the expression of antioxidant response elements and cytoprotective genes and modulate inflammatory response, helping to ameliorate damage in many diseases. Exactly how Nrf2 regulates innate inflammatory homeostasis remains unclear. In this study, we provide in vitro and in vivo evidence that Nrf2 plays a crucial role in macrophage polarization and acute respiratory distress syndrome (ARDS). We conducted in vitro experiments using a mouse alveolar macrophage cell line as well as primary cultures of macrophages in which cells were exposed to lipopolysaccharide (LPS) or interferon-γ in order to mimic ARDS, in the presence or absence of the Nrf2 activator tert-butylhydroquinone (tBHQ). Using siRNA-mediated Nrf2 knockdown, we showed that Nrf2 inhibited the inflammatory response by promoting M2 macrophage polarization and inhibiting M1 macrophage polarization. At the same time, tBHQ activated Nrf2-mediated inhibition of the p65 nuclear factor-κB pathway and activation of peroxisome proliferator-activated receptor-γ, which play important roles in regulating macrophage polarization. We also conducted in vivo experiments in which mice were given tBHQ with or without intratracheal LPS, then their survival was monitored, lung injury was assessed using histology, and levels of pro- and anti-inflammatory cytokines were assayed in the lungs and serum. Activation of Nrf2 with tBHQ dramatically reduced LPS-induced mortality and lung injury, down-regulated pro-inflammatory mediators and up-regulated anti-inflammatory mediators. These results suggest that Nrf2 can help prevent ARDS progression by promoting M2 polarization of macrophages. Interfering with Nrf2 may be an effective strategy for reprogramming macrophage polarization in order to treat ARDS.

[en] Perovskite solar cells (PSCs) have rapidly developed in recent years with the advantages of high efficiency and low cost. Although PSCs are the fastest-advancing solar technology to date, bottlenecks such as J–V hysteresis have limited the further development significantly. In this work, we have investigated the in-depth mechanism of hysteresis in both three-dimensional (3D) and quasi-2D (Q-2D) planar p-i-n PSCs. We conducted scanning-rate-dependent and temperature-dependent measurements to distinguish the ion migration and the capacitive charging. The coefficient for capacitance and pseudocapacitance from the J–V curves are further employed to analysis the hysteresis. It is found that both capacitance and ion migration contribute to the J–V hysteresis, but play different roles in 3D and Q-2D perovskite devices. In 3D PSCs, the ion migration has substantial impacts on the J–V hysteresis, wherein ions are tending to move. While in the Q-2D PSCs, the capacitance extends the characteristic charging time, which is mainly responsible for J–V hysteresis. These findings will help to effectively suppress the hysteresis for 3D and Q-2D PSCs, eventually benefiting device performance and long term stability. (paper)

[en] Highlights: • A simple solution process was exploited to obtain perovskite nanostructure assembly. • The perovskite solar cell with nanostructure assembly yields a PCE of 19.16%. • The adoption of perovskite nanostructure assembly leads to photon management. • The photon management is due to the localized gratings and fluorescence effect. • The presentation of fluorescence resonance energy transfer in perovskite solar cell. Organic-inorganic perovskite solar cells have been highlighted as one of the most competitive thin film photovoltaics recently. It is promising to further raise the power conversion efficiency if high quality absorber is coupled with rational optical design for effective photon management. Here we demonstrate the implementation of perovskite nanostructure assembly by simple solution process to interfere the propagation of light inside the adjacent absorber. It enhances light harvesting to obtain higher attainable photocurrents and photovoltage in the resultant devices, achieving a decent power conversion efficiency (PCE) over 19% consequently. The presented nanostructure assembly integrates perovskite materials with desirable processibility and chemical compatibility by chemical synthesis and interface modification. For the first time, a synergetic localized “gratings” and enhanced fluorescence effect was demonstrated to govern photon management in perovskite solar cells. These findings may serve as a general guide to design and construct perovskite thin solar cells with efficiency approaching Shockley-Queisser limit.

[en] Highlights: • The CdTe-QD-in-perovskite solids were synthesized and used as modifier in perovskite solar cells. • The CdTe-QD-in-perovskite solids modified solar cells exhibited high efficiency (averaged 19.3%) and negligible hysteresis. • The influence of surface ligands of CdTe QDs on device performance are studied. Solar cells employing lead halide perovskites as light absorbers have been one hot topic in recent years due to their amazing device performance and commercialization potential. Yet, there exist challenges on the way to their practical use, including long-term stability, and J-V hysteresis. Herein, we demonstrate an improved contact between perovskite and hole transporting layer (HTL) by using CdTe quantum dots, wherein the capping ligands on quantum dots are systematically investigated. The devices with the CdTe quantum-dot-in-perovskite solids interlayer achieve a high efficiency (~ 19.3%, averaged), and more importantly, a significantly reduced hysteresis, which is superior to devices with CdTe QDs capped by other ligands (PbI₂, CH₃NH₃I, oleic acid). We attribute this superior device performance to the congeneric junction contact between perovskite and CdTe quantum-dot-in-perovskite layer. Furthermore, we reveal that the reduced hysteresis is partially contributed from faster hole extraction at the interface thanks to the high hole mobility in CdTe. These findings shed lights on the future design of quantum dots for perovskite optoelectronics in the perspective of ligand engineering.

[en] Uniform Ce_1-xZr_xO₂ (x=0.2-0.8) nanocrystals with ultra-small size were synthesized through a thermolysis process, facilitated by the initial formation of precursor (hydrated (Ce,Zr)-hydroxides) at low temperature. TEM, XRD, EDAX, and Raman spectra were employed to study the formation of the solid solutions with various Ce/Zr ratios. Ultraviolet-visible (UV-vis) spectra showed that the ratios of Ce³⁺ to Ce⁴⁺ in both surface and bulk for the as-prepared Ce_1-xZr_xO₂ nanocrystals increased with the zirconium content x. The well-distributed Zr and Ce in the hydrated (Ce,Zr)-hydroxides before their thermolysis became the crucial factor for the structural homogeneity of the products. In addition, this strategy was extended to the synthesis of Ce_1-xGd_xO_1-x/2, Ce_1-xSm_xO_1-x/2, and Ce_1-xSn_xO₂ solid solutions. Catalytic measurements indicated that the ceria-based catalysts were active for CO oxidation at temperatures beyond 250 deg. C and the sequence of catalytic activity was Ce_0.5Zr_0.5O₂>Ce_0.8Zr_0.2O₂>Ce_0.2Zr_0.8O₂>Ce_0.5Sm_0.5O_1.75. - Abstract: Uniform ultra-small nanostructured Ce_1-xZr_xO₂, Ce_1-xGd_xO_1-x/2, Ce_1-xSm_xO_1-x/2, and Ce_1-xSn_xO₂ solid solutions with homogeneous textures were synthesized through a thermolysis process, facilitated by the initial formation of precursors (hydrated (Ce,M)-hydroxides). Display Omitted

[en] Perovskite solar cells (PSCs) have become a promising candidate for the next-generation photovoltaic technologies. As an essential element for high-efficiency PSCs however, the heavy metal Pb is soluble in water, causing a serious threat to the environment and human health. Due to the weak ionic bonding in three-dimensional (3D) perovskites, drastic structure decomposition occurs when immersing the perovskite film in water, which accelerates the Pb leakage. By introducing the chemically stable Dion-Jacobson (DJ) 2D perovskite at the 3D perovskite surface, the film dissolution is significantly slowed down, which retards lead leakage. As a result, the Pb contamination is dramatically reduced under various extreme conditions. In addition, the PSCs device deliver a power conversion efficiency (PCE) of 23.6 % and retain over 95 % of their initial PCE after the maximum power point tracking for over 1100 h. (© 2022 Wiley‐VCH GmbH)

[en] Lead halide perovskites with mixed cations/anions often suffer from phase segregation, which is detrimental to device efficiency and their long-term stability. During perovskite film growth, the gel stage (in between liquid and crystalline) correlates to phase segregation, which has been rarely explored. Herein, cation diffusion kinetics are systematically investigated at the gel stage to develop a diffusion model obeying Fick's second law. Taking 2D layered perovskite as an example, theoretical and experimental results reveal the impact of diffusion coefficient, temperature, and gel duration on the film growth and phase formation. A homogenous 2D perovskite thin film was then fabricated without significant phase segregation. This in-depth understanding of gel stage and relevant cation diffusion kinetics would further guide the design and processing of halide perovskites with mixed composition to meet requirements for optoelectronic applications. (© 2020 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

[en] Possessed with advantageous optoelectronic properties, perovskites have boosted the rapid development of solution-processed solar cells. The performance of perovskite solar cells (PSCs) is significantly weakened by the carrier loss at grain boundary grooves (GBGs); however, it receives limited attention and there lacks effective approach to solve this issue. Herein, for the first time, we constructed the tungstate/perovskite heterointerface via a "two step" in situ reaction approach that provides effective defect passivation and ensures efficient carrier dynamics at the GBGs. The exposed perovskite at grain boundaries is converted to wide-band-gap PbWO${}_4$ via an in-situ reaction between Pb${}^{2+}$ and tungstate ions, which passivate defects due to the strong ionic bonding. Moreover, recombination loss is further suppressed via the heterointerface energetics modification based on an additional transformation from PbWO${}_4$ to CaWO${}_4$. PSCs based on this groove modification strategy showed good universality in both normal and inverted structure, with an improved efficiency of 23.25 % in the n-i-p device and 23.33 % in the p-i-n device. Stable power output of the modified device could maintain 91.7 % after around 1100 h, and the device efficiency could retain 92.5 % after aging in air for around 2110 h, and 93.1 % after aging at 85 °C in N${}_2$ for 972 h. (© 2023 Wiley‐VCH GmbH)