Publications by authors named "Nicholas Rolston"

Hybrid metal halide perovskite (MHP) materials, while being promising for photovoltaic technology, also encounter challenges related to material stability. Combining 2D MHPs with 3D MHPs offers a viable solution, yet there is a gap in the understanding of the stability among various 2D materials. The mechanical, ionic, and environmental stability of various 2D MHP ligands are reported, and an improvement with the use of a quater-thiophene-based organic cation (4TmI) that forms an organic-semiconductor incorporated MHP structure is demonstrated.

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We report on the use of 2D Ruddlesden-Popper (RP) perovskites as optoelectronic materials in building-integrated applications, addressing the challenge of balancing transparency, photoluminescence, and stability. With the addition of polyvinylpyrrolidone (PVP), the 2D RP films exhibit superior transparency compared to their 3D counterparts with an average visible transmittance (AVT) greater than 50% and photoluminescence stability under continuous illumination and 85 °C heat for up to 100 h as bare, unencapsulated films. Structural investigations show a stress relaxation in the 3D perovskite films after degradation from thermal aging that is not observed in the 2D RP films, which retain their phase after thermal and light aging.

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Inverted (pin) perovskite solar cells (PSCs) afford improved operating stability in comparison to their nip counterparts but have lagged in power conversion efficiency (PCE). The energetic losses responsible for this PCE deficit in pin PSCs occur primarily at the interfaces between the perovskite and the charge-transport layers. Additive and surface treatments that use passivating ligands usually bind to a single active binding site: This dense packing of electrically resistive passivants perpendicular to the surface may limit the fill factor in pin PSCs.

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Challenges to upscaling metal halide perovskites (MHPs) include mechanical film stresses that accelerate degradation, dominate at the module scale, and can lead to delamination or fracture. In this work, we demonstrate open-air blade coating of single-step coated perovskite as a scalable method to control residual film stress after processing and introduce beneficial compression in the thin film with the use of polymer additives such as gellan gum and corn starch. The optoelectronic properties of MHP films with compression are improved with higher photoluminescence yields.

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State-of-the-art solid-state electrolytes (SSEs) are limited in their energy density and processability based on thick, brittle pellets, which are generally hot pressed in vacuum over the course of several hours. We report on a high-throughput, open-air process for printable thin-film ceramic SSEs in a remarkable one-minute time frame using a lithium lanthanum titanium oxide (LLTO)-based SSE that we refer to as robust LLTO (R-LLTO). Powder XRD analysis revealed that the main phase of R-LLTO is polycrystalline LLTO, accompanied by selectively retained crystalline precursor phases.

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The presence of intrinsic ion migration in metal halide perovskites (MHPs) is one of the main reasons that perovskite solar cells (PSCs) are not stable under operation. In this work, we quantify the ion migration of PSCs and MHP thin films in terms of mobile ion concentration (N) and ionic mobility (µ) and demonstrate that N has a larger impact on device stability. We study the effect of small alkali metal A-site cation additives (e.

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Herein, we focus on improving the long-term chemical and thermomechanical stability of perovskite solar cells (PSCs), two major challenges currently limiting their commercial deployment. Our strategy incorporates a long-chain starch polymer into the perovskite precursor. The starch polymer confers multiple beneficial effects by forming hydrogen bonds with the methylammonium iodide precursor, templating perovskite growth that results in a compact and homogeneous film deposited in a simple one-step coating (antisolvent-free).

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Emerging moisture sensitive devices require robust encapsulation strategies to inhibit water ingress and prevent premature failure. A scalable, open-air plasma process has been developed to deposit alternating layers of conformal organosilicate and dense SiO thin-film barriers to prevent moisture ingress. The in situ low-temperature process is suitable for direct deposition on thermally sensitive devices and is compatible with flexible polymeric substrates.

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Tsai (Reports, 6 April 2018, p. 67) report a uniform light-induced lattice expansion of metal halide perovskite films under 1-sun illumination and claim to exclude heat-induced lattice expansion. We show that by controlling the temperature of the perovskite film under both dark and illuminated conditions, the mechanism for lattice expansion is in fact fully consistent with heat-induced thermal expansion during illumination.

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Despite rapid progress of hybrid organic-inorganic halide perovskite solar cells, using transmission electron microscopy to study their atomic structures has not been possible because of their extreme sensitivity to electron beam irradiation and environmental exposure. Here, we develop cryogenic-electron microscopy (cryo-EM) protocols to preserve an extremely sensitive perovskite, methylammonium lead iodide (MAPbI) under various operating conditions for atomic-resolution imaging. We discover the precipitation of lead iodide nanoparticles on MAPbI nanowire's surface after short UV illumination and surface roughening after only 10 s exposure to air, while these effects remain undetected in conventional x-ray diffraction.

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Article Synopsis
  • Scientists studied how changing the size of molecules in a special material called PTAA can make it stronger and help solar panels work better.
  • They tested different sizes to see how well the solar panels convert sunlight into power and how well they hold up in humid conditions.
  • They found that bigger molecules make the PTAA films stronger and that adding certain small chemicals helps make them even more stable.
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Phenyl-C-butyric acid methyl ester (PCBM) is universally used as the electron-transport layer (ETL) in the low-cost inverted planar structure of perovskite solar cells (PeSCs). PCBM brings tremendous challenges in upscaling of PeSCs using industry-relevant methods due to its aggregation behavior, which undermines the power conversion efficiency and stability. Herein, we highlight these, seldom reported, challenges with PCBM.

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The active layers of perovskite solar cells are also structural layers and are central to ensuring that the structural integrity of the device is maintained over its operational lifetime. Our work evaluating the fracture energies of conventional and inverted solution-processed MAPbI perovskite solar cells has revealed that the MAPbI perovskite exhibits a fracture resistance of only ∼0.5 J/m, while solar cells containing fullerene electron transport layers fracture at even lower values, below ∼0.

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