RESUMEN
High-purity precursor materials are vital for high-efficiency perovskite solar cells (PSCs) to reduce defect density caused by impurities in perovskite. In this study, we present aqueous synthesized perovskite microcrystals as precursor materials for PSCs. Our approach enables kilogram-scale mass production and synthesizes formamidinium lead iodide (FAPbI3) microcrystals with up to 99.996% purity, with an average value of 99.994 ± 0.0015%, from inexpensive, low-purity raw materials. The reduction in calcium ions, which made up the largest impurity in the aqueous solution, led to the greatest reduction in carrier trap states, and its deliberate introduction was shown to decrease device performance. With these purified precursors, we achieved a power conversion efficiency (PCE) of 25.6% (25.3% certified) in inverted PSCs and retained 94% of the initial PCE after 1000 hours of continuous simulated solar illumination at 50°C.
RESUMEN
Nickel oxide (NiOx ) is one of the most promising hole transport materials for inverted perovskite solar cells (PSCs). However, its application is severely restrained due to unfavorable interfacial reactions and insufficient charge carrier extraction. Herein, a multifunctional modification at the NiOx /perovskite interface is developed via introducing fluorinated ammonium salt ligand to synthetically solve the obstacles. Specifically, the interface modification can chemically convert detrimental Ni≥3+ to lower oxidation state, resulting in the elimination of interfacial redox reactions. Meanwhile, interfacial dipole is incorporated simultaneously to tune the work function of NiOx and optimize energy level alignment, which effectively promotes the charge carrier extraction. Therefore, the modified NiOx -based inverted PSCs achieve a remarkable power conversion efficiency (PCE) of 22.93%. Moreover, the unencapsulated devices obtain a significantly enhanced long-term stability, maintaining over 85% and 80% of the initial PCEs after storage in ambient air with a high relative humidity of 50-60% for 1000 h and continuous operation at maximum power point under one-sun illumination for 700 h, respectively.
RESUMEN
Post-treatment has been recognized as one of the effective methods for passivating the underlying defects in perovskite solar cells (PSCs), but little attention has been paid to how to pick suitable passivation agents with diverse isomers for efficient PSCs, particularly for the tin-lead (Sn-Pb) mixed PSCs. Here, we introduce the dependence of the power conversion efficiency (PCE) on a dipole moment for surface passivator screening, in which we chose three trifluoromethyl-phenylethylamine hydroiodide (CF3-PEAI) isomers as surface-treatment materials for hole-transport-layer-free (HTL-free) Sn-Pb mixed PSCs. The different positions of the -CF3 group for the CF3-PEAI isomer result in different dipole moments, which influences the interaction between CF3-PEAI and lead iodide. The para position CF3 with the highest dipole moment exhibits a higher PCE than the ortho-position with a lower dipole moment, which is attributed to the large dipole moment on the surface that could tune the surface polarity from p-type to n-type, facilitating electron charge transport in the HTL-free Sn-Pb mixed PSCs. An ultrathin 2D layer is formed on the perovskite surface to passivate the surface defects, which is responsible for the enhancement of the PCE and stability of the PSCs. As a result, the open-circuit voltage (VOC) of the device is improved from 0.775 to 0.824 V, yielding a champion PCE of 20.17%, which is one of the highest PCEs among the reported HTL-free Sn-Pb mixed PSCs. The device also shows improved stability with remaining 75% of its initial PCEs after storage in N2 for 700 h.
RESUMEN
A H2SO4-Ti3C2Tx ion-gel is in situ fabricated to prevent the restacking of Ti3C2Tx for high-rate micro-supercapacitors. The ion-gel pillared by an electrolyte possesses an enlarged interlayer spacing facilitating ion transport. Furthermore, a bilayer structure is designed with dry Ti3C2Tx for fast electron conduction. The bilayer Ti3C2Tx film shows improved capacitance from 49% to 73% of the initial capacitance at a high scan rate of 200 mV s-1, along with excellent cycle stability. This study opens up a concise and efficient way for high-performance micro-supercapacitors.
RESUMEN
The development of cost-effective electrocatalysts with high activity and sufficient stability for hydrogen evolution reaction (HER) is crucial for the widespread application of water electrolysis for sustainable H2 production. Transition metal oxides are desirable alternatives to replace benchmark Pt-based HER electrocatalysts because of their cost effectiveness, facile synthesis, versatile compositions, and easy electronic structure tuning. However, most available transition metal oxides show poor performance for HER catalysis. Here, it is reported that the anatase TiO2 can be efficiently developed into a superior HER electrocatalyst with comparable activity to Pt-based electrocatalysts in alkaline solution through simultaneous morphology control, proper lattice doping, and surface active sites engineering. Specifically, the obtained cobalt-doped TiO2 nanorod arrays (Co-TiO2 @Ti(H2 )) show a low overpotential of only 78 mV at 10 mA cm-2 , a small Tafel plot of 67.8 mV dec-1 , and excellent stability even at an ultralarge current density of ≈480 mA cm-2 in 1.0 m KOH solution. Theoretical calculations demonstrate that the introduction of Co with rich oxygen vacancies can efficiently lower the energy barrier for water adsorption/dissociation and H intermediate desorption. This work uncovers the potential of the low-cost transition metal oxides as alternative HER electrocatalysts in alkaline water electrolysis.
RESUMEN
Tin-lead (Sn-Pb) perovskites have shown great potential in applications of single-junction perovskite solar cells (PSCs) and tandem devices due to outstanding photoelectrical properties and low band gaps. Currently, Sn-Pb PSCs typically have a p-i-n structure, but choices of hole transport layer (HTL) materials are very limited and there are different concerns in each of them. Eliminating the HTL is a direct and promising strategy to address the concerns, but is rarely studied. In this work, we demonstrate HTL-free and MA-free based Sn-Pb PSCs and a synergistic integration strategy of simultaneously introducing a reducing agent and in situ surface passivation. With the integration strategy, Sn-Pb perovskite films with enhanced antioxidation, reduced trap density, prolonged carrier lifetime, and improved energy-level alignment are achieved. Consequently, final HTL-free PSCs exhibit a champion power conversion efficiency (PCE) of 17.4%, which is a new record for HTL-free and MA-free Sn-Pb PSCs. Meanwhile, the integration strategy-based HTL-free device maintains excellent stability with efficiency unchanged for the first 200 h, and finally retaining 81% of the efficiency after 480 h aging in the air. This study shows the potential of achieving desirable HTL-free and MA-free Sn-Pb PSCs and offers more opportunities for tandem solar cells and other photovoltaic devices.
RESUMEN
Rational design of unique pre-catalysts for highly active catalysts toward catalyzing the oxygen evolution reaction (OER) is a great challenge. Herein, a Co-derived pre-catalyst that allows gradual exposure of CoOOH that acts as the active center for OER catalysis is obtained by both phosphate ion surface functionalization and Mo inner doping. The obtained catalyst reveals an excellent OER activity with a low overpotential of 265 mV at a current density of 10 mA cm-2 and good durability in alkaline electrolyte, which is comparable to the majority of Co-based OER catalysts. Specifically, the surface functionalization produces lots of Co-PO4 species with oxygen vacancies which can trigger the surface self-reconstruction of pre-catalyst for a favorable OER reaction. Density functional theory calculations reveal that the Mo doping optimizes adsorption-free energy of *OOH formation and thus accelerates intrinsic electrocatalytic activity. Expanding on these explorations, a series of transition metal oxide pre-catalysts are obtained using this general design strategy. The work offers a fundamental understanding toward the correlation among surface-structure-activity for the pre-catalyst design.
