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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Anion and Cation Migration at 2D/3D Halide Perovskite Interfaces

Here, this study explores the ionic dynamics in 2D/3Dperovskite solar cells, which are known for their improved efficiency and stability. The focus is on the impact of halide choice in 3D perovskites treated with phenethylammonium halide salts (PEAX, X = Br and I). Our findings reveal that light and heat drive ionic migration in these structures, with PEA + species diffusing into the 3D film in PEABr-treated samples. Mixed-halide 3D perovskites show halide interdiffusion, with bromine migrating to the surface and iodine diffusing into the film. Cathodoluminescence microscopy reveals localized 2Dphases on the 3D perovskite, which become more evenly distributed after thermal treatment. Both PEAX salts enhance the performance of photovoltaic devices. This improvement is attributed to the passivation capabilities of the salts themselves and their respective Ruddlesden–Popper (RP) phases. Annealed PEAI-treated devices show a better balance between efficiency and statistical distribution of photovoltaic parameters.

25 ENERGY STORAGE↗
DOE OSTI2020

All-Inorganic Halide Perovskites as Potential Thermoelectric Materials: Dynamic Cation off-Centering Induces Ultralow Thermal Conductivity

Halide perovskites are anticipated to impact next generation high performance solar cells because of their extraordinary charge transport and optoelectronic properties. However, their thermal transport behavior has received limited attention. In this work, we studied the thermal transport and thermoelectric properties of the CsSnBr 3–x I x perovskites. We find a strong correlation between lattice dynamics and an ultralow thermal conductivity for series CsSnBr 3–x I x reaching 0.32 Wm –1 K –1 at 550 K. The CsSnBr 3–x I x also possess a decent Seebeck coefficient and controllable electrical transport properties. The crystallography data and theoretical calculations suggest the Cs atom deviates from its ideal cuboctahedral geometry imposed by the perovskite cage and behaves as a heavy atom rattling oscillator. This off-center tendency of Cs, together with the distortion of SnX 6 (X = Br or I) octahedra, produces a highly dynamic and disordered structure in CsSnBr 3–x I x , which gives rise to a very low Debye temperature and phonon velocity. Moreover, the low temperature heat capacity data suggests strong coupling between the low frequency optical phonons and heat carrying acoustical phonons. In conclusion, this induces strong phonon resonance scattering that induces the ultralow lattice thermal conductivity of CsSnBr 3–x I x .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗