Journal: Nature materials

Article Title: Intrinsic quantum confinement in formamidinium lead triiodide perovskite.

doi: 10.1038/s41563-020-0774-9

Figure Lengend Snippet: Fig. 1 | Temperature-dependent absorption coefficient and peak features. a,b, Absorption spectra (a) and peaks (b) for a 297-nm-thick FAPbI3 film measured by FTIR spectroscopy at roughly 70 K temperature intervals from 4 K to 295 K (the legend in a also applies to b). Spectra for further temperatures and film thicknesses are shown in Supplementary Figure 5. For clarity, spectra and peaks at successively decreasing temperatures are offset vertically by 1.5 × 103 cm−1 and 1 × 102 cm−1 respectively. The inset in a depicts the reflectance and transmittance of the film at 4 K. The inset in b shows the absorption coefficient (α) at 4 K with its absorption onset fitted by a function based on Elliott’s theory (dotted black line) and the oscillatory region fitted with a spline baseline fit (solid black line), which is subtracted from the absorption coefficient to give the peaks shown in b.

Article Snippet: X-ray diffraction patterns of FAPbI3 films were measured in air using a Panalytical X’pert powder diffractometer with a copper X-ray source.

Techniques: Spectroscopy

Journal: Nature materials

Article Title: Intrinsic quantum confinement in formamidinium lead triiodide perovskite.

doi: 10.1038/s41563-020-0774-9

Figure Lengend Snippet: Fig. 2 | Temperature dependence of the optoelectronic and lattice properties of FAPbI3. a, Eg extracted from Elliott fits to the absorption spectra for films of six thicknesses (see the legend). b, Linewidth (full-width at half-maximum, FHWM) of the excitonic peak extracted from the Elliott fits (red squares) and the most prominent peaks (blue triangles), averaged across the six film thicknesses. The dark solid lines are fits that account for Fröhlich coupling with LO phonons, excluding temperatures near the phase transition (dotted lines). Error bars show the standard error. c, Epeak relative to Eg. Boxed numbers show the peak indices. d, Variation of Epeak − Eg (magenta dots) at 4 K in the 297-nm-thick film as a function of the peak index. The solid blue line is a fit based on a quadratic function whereas the black squares represent Eg values derived from a Krönig–Penney potential (see Supplementary Note 7). The offset of the lowest-energy peaks from Eg may be attributed to a slightly higher bandgap within the nanostructures, shifted by ∼70 meV due to lattice strain within the nanostructure9,23. e, Integral (area) under the main peaks (black squares) as a percentage of the total area under the spectrum, averaged across the six thicknesses. Error bars show the standard error. f, Temperature dependence of 1/p2 for p defined in the legend. The inset shows Q, which is given by the ratio of the temperature gradients in Epeak − Eg to those in 1/p2 for the 297-nm-thick film (see Supplementary Note 8). Panel f adapted with permission from ref. 34, American Chemical Society.

Article Snippet: X-ray diffraction patterns of FAPbI3 films were measured in air using a Panalytical X’pert powder diffractometer with a copper X-ray source.

Techniques: Sublimation, Derivative Assay

Journal: Energy & Environmental Science

Article Title: Triple-junction perovskite–perovskite–silicon solar cells with power conversion efficiency of 24.4% †

doi: 10.1039/d3ee03687a

Figure Lengend Snippet: Characteristics of non-radiative recombination for middle sub-cell. (a) TRPLs and (b) PLQYs for ITO/2PACz/FAPbI 3 and ITO/2PACz/FAPbI 3 /C 60 /SnO x stacks. (c) EL imaging of opaque and semitransparent single-junction FAPbI3-based devices. (d) Trap density obtained from the SCLC method, (e) light intensity dependence of the V OC , and (f) normalized transient photovoltage decay of semitransparent FAPbI 3 -based devices.

Article Snippet: XRD was performed on the layer stack of ITO/2PACz/FAPbI 3 using a Bruker D2Phaser system with Cu-Kα radiation ( λ = 1.5405 Å) in Bragg–Brentano configuration using a LynxEye detector.

Techniques: Imaging