Perovskite solar cells (PSCs) consisting of interfacial two- and three-dimensional heterostructures that incorporate ammonium ligand intercalation have enabled rapid progress toward the goal of uniting performance with stability. However, as the field continues to seek ever-higher durability, additional tools that avoid progressive ligand intercalation are needed to minimize degradation at high temperatures. We used ammonium ligands that are nonreactive with the bulk of perovskites and investigated a library that varies ligand molecular structure systematically. We found that fluorinated aniliniums offer interfacial passivation and simultaneously minimize reactivity with perovskites. Using this approach, we report a certified quasi–steady-state power-conversion efficiency of 24.09% for inverted-structure PSCs. In an encapsulated device operating at 85°C and 50% relative humidity, we document a 1560-hour
T
85
at maximum power point under 1-sun illumination.
Further improvements in the photovoltaic performance of B-site alloyed organic−inorganic halide perovskites (OIHPs) will rely on accurate modeling of defect properties and passivation strategies. Herein, we report that B-site alloying results in defect behaviors distinct from those of pure OIHPs, a finding obtained by uniting first-principles calculations with experimental measurements. We identify from computational studies a defect-tolerant region spanning a Sn content of 30−70% in mixed Pb-Sn perovskites and experimentally observe notably longer carrier lifetimes in 50% Sn mixed perovskite films than at other Sn contents. We discuss a strategy of applying defect-tolerant 50% Pb-Sn perovskites in ideal-bandgap (1.3−1.4 eV) active layer materials which conventionally rely on 25−30% Sn compositions. The composition (FA 0.75 Cs 0.25 Pb 0.5 Sn 0.5 (I 0.9 Br 0.1 ) 3 ) achieves increased carrier lifetimes of >1 μs. This work reveals a general trend in defect tolerance for B-site alloying: a higher valence band maximum (lower conduction band minimum), along with strengthened ionic bonding, can potentially contribute to improved photovoltaic performance.
methyl resonance (not shown) is a doublet at 1.37 ppm vs. DSS and has a spacing of 6.0 Hz. Of the three protons remaining on the propylenediamine backbone, it appears that Ha produces the triplet-like resonance at highest field, and that Hb and Hc are almost coincident at lowest field. The triplet-like resonance of Ha results from spin coupling to Hb and Hc with nearly equal magnitudes (/ab « -12.5 and /ac 11.0 Hz).6•7Simultaneous irradiation of cobalt-59 and the methyl doublet leads to changes in the low-field portion of Figure 2B which are consistent with the assignment of Hc. The approximate chemical shifts are ¿a ~2.48, ¿b ~2.93, and ¿c ~3.05 ppm vs. DSS. Use of solvent shifts and a higher spectrometer frequency spreads out the spectrum sufficiently for a complete analysis, now in progress.The sharpness of the Ha lines compared to the Hb lines tends to indicate that the Co-N-C-H coupling constant is greater for equatorial protons than for axial protons. A similar result is evident for Co(en)31 23+ in Figure 1C.21 This finding, in addition to the fact that ¿b > Sa in L-[Co(( -)pn)3]3+ supports the assignment of ¿axia¡ <~2.75 ppm and ¿equatorial ~2.93 ppm in Co(en)33+.
Phytoglycogen (PG) is a polysaccharide produced in the kernels of sweet corn as soft, highly branched, compact nanoparticles. Its tree-like or dendritic architecture, combined with a high-safety profile, makes PG nanoparticles attractive for use in biological applications, many of which rely on the association or binding of small biomolecules. We have developed a methodology to functionalize surface plasmon resonance (SPR) sensor surfaces with PG nanoparticles, and we demonstrate the utility of the PG-functionalized SPR sensor by measuring the binding affinity of the tetrameric concanavalin A (ConA) protein to both native PG nanoparticles and smaller, softer acid-hydrolyzed PG nanoparticles. We measure comparable values of the equilibrium association constant K for native and acid-hydrolyzed PG, with a slightly smaller value for the acid-hydrolyzed particles that we attribute to unfavorable lateral interactions between the tetrameric subunits of ConA due to the increase in surface curvature of the smaller acid-hydrolyzed PG particles. We also use infrared reflection-absorption spectroscopy (IRRAS) to show that ConA maintains a large fraction of its native conformation, and thus its bioactivity, upon binding to PG, representing an important step toward the realization of PG as a novel bioactive delivery vehicle.
Band gap tuning in mixed-halide perovskites enables efficient
multijunction
solar cells and LEDs. However, these wide band gap perovskites, which
contain a mixture of iodide and bromide ions, are known to phase segregate
under illumination, introducing voltage losses that limit stability.
Previous studies have employed inorganic perovskites, halide alloys,
and grain/interface passivation to minimize halide segregation, yet
photostability can be further advanced. By focusing on the role of
halide vacancies in anion migration, one expects to be able to erect
local barriers to ion migration. To achieve this, we employ a 3D “hollow”
perovskite structure, wherein a molecule that is otherwise too large
for the perovskite lattice is incorporated. The amount of hollowing
agent, ethane-1,2-diammonium dihydroiodide (EDA), varies the density
of the hollow sites. Photoluminescence measurements reveal that 1%
EDA in the perovskite bulk can stabilize a 40% bromine mixed-halide
perovskite at 1 sun illumination intensity. These, along with capacitance–frequency
measurements, suggest that hollow sites limit the mobility of the
halide vacancies.
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