No abstract

E. H. (2022). Quantum-size-tuned heterostructures enable efficient and stable inverted perovskite solar cells. Nature Photonics.

E. H. (2022). Regulating surface potential maximizes voltage in all-perovskite tandems. Nature.

Lewis base molecules that bind undercoordinated lead atoms at interfaces and grain boundaries (GBs) are known to enhance the durability of metal halide perovskite solar cells (PSCs). Using density functional theory calculations, we found that phosphine-containing molecules have the strongest binding energy among members of a library of Lewis base molecules studied herein. Experimentally, we found that the best inverted PSC treated with 1,3-bis(diphenylphosphino)propane (DPPP), a diphosphine Lewis base that passivates, binds, and bridges interfaces and GBs, retained a power conversion efficiency (PCE) slightly higher than its initial PCE of ~23% after continuous operation under simulated AM1.5 illumination at the maximum power point and at ~40°C for >3500 hours. DPPP-treated devices showed a similar increase in PCE after being kept under open-circuit conditions at 85°C for >1500 hours.

The epitaxial growth of a perovskite matrix on quantum dots (QDs) has enabled the emergence of efficient red light-emitting diodes (LEDs) because it unites efficient charge transport with strong surface passivation. However, the synthesis of wide-band gap (E g) QD-in-matrix heterostructures has so far remained elusive in the case of sky-blue LEDs. Here, we developed CsPbBr3 QD-in-perovskite matrix solids that enable high luminescent efficiency and spectral stability with an optical E g of over 2.6 eV. We screened alloy candidates that modulate the perovskite E g and allow heteroepitaxy, seeking to implement lattice-matched type-I band alignment. Specifically, we introduced a CsPb1–x Sr x Br3 matrix, in which alloying with Sr2+ increased the E g of the perovskite and minimized lattice mismatch. We then developed an approach to passivation that would overcome the hygroscopic nature of Sr2+. We found that bis(4-fluorophenyl)­phenylphosphine oxide strongly coordinates with Sr2+ and provides steric hindrance to block H2O, a finding obtained by combining molecular dynamics simulations with experimental results. The resulting QD-in-matrix solids exhibit enhanced air- and photo-stability with efficient charge transport from the matrix to the QDs. LEDs made from this material exhibit an external quantum efficiency of 13.8% and a brightness exceeding 6000 cd m–2.

No abstract

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.

We report on the unique vibrational properties of 2D anisotropic orthorhombic tantalum trisulfide (o-TaS3) measured through angle-resolved Raman spectroscopy and high-pressure diamond anvil cell studies. Our broad-spectrum Raman measurements identify optical and low-frequency shear modes in pseudo-1D o-TaS3 for the first time, and introduce their polarization resolved Raman responses to understand atomic vibrations for these modes. Results show that, unlike other anisotropic systems, only the S∥ mode at 54 cm–1 can be utilized to identify the crystalline orientation of TaS3. More notably, high-pressure Raman measurements reveal previously unknown four distinct types of responses to applied pressure, including positive, negative, and nonmonotonic dω/dP behaviors which are found to be closely linked to atomic vibrations for involving these modes. Our results also reveal that the material approaches an isotropic limit under applied pressure, evidenced by a significant reduction in the degree of anisotropy. Overall, these findings significantly advance not only our understanding of their fundamental properties of pseudo-1D materials but also our interpretations of the vibrational characteristics that offer valuable insights about thermal, electrical, and optical properties of pseudo-1D material systems.