Daily temperature variations induce phase transitions and lattice strains in halide perovskites, challenging their stability in solar cells. We stabilized the perovskite black phase and improved solar cell performance using the ordered dipolar structure of β-poly(1,1-difluoroethylene) to control perovskite film crystallization and energy alignment. We demonstrated p-i-n perovskite solar cells with a record power conversion efficiency of 24.6% over 18 square millimeters and 23.1% over 1 square centimeter, which retained 96 and 88% of the efficiency after 1000 hours of 1-sun maximum power point tracking at 25° and 75°C, respectively. Devices under rapid thermal cycling between −60° and +80°C showed no sign of fatigue, demonstrating the impact of the ordered dipolar structure on the operational stability of perovskite solar cells.
Single NV centers in HPHT IIa diamond are fabricated by helium implantation through lithographic masks. The concentrations of created NV centers in different growth sectors of HPHT are compared quantitatively. It is shown that the purest {001} growth sector (GS) of HPHT diamond allows to create groups of single NV centers in predetermined locations. The {001} GS HPHT diamond is thus considered a good material for applications that involve single NV centers.
Abstract— The effect of the formation of a periodic surface microrelief while stretching the polymeric substrates with thin hard coatings under specified conditions (a processing temperature lower than the glassing temperature, an elongation magnitude up to 250%, an elongation velocity <5 mm/min) is described. The microrelief period varies in the range from 0.5 μm up to hundreds of micrometers, the height up to 1 μm. The polar and azimuthal orientation of a liquid crystal on the surface of such substrates was studied. Methods are proposed to measure low values of the optical path length in media Δn ∼ λ and components of LC anchoring energy on microreliefed surfaces. The simulation description of the light diffraction in optical anisotropic materials is proposed on the basis of the Rokushima‐Yamakita approach for periodical media. An opportunity for the creation of various optical components on the basis of this effect was considered, namely, diffraction gratings, optical compensators, and various types of light‐scattering elements.
Nitrogen-vacancy (NV) color centers in diamond are excellent quantum sensors possessing high sensitivity and nano-scale spatial resolution. Their integration in photonic structures is often desired, since it leads to an increased photon emission and also allows the realization of solid-state quantum technology architectures. Here, we report the fabrication of diamond nano-pillars with diameters up to 1000 nm by electron beam lithography and inductively coupled plasma reactive ion etching in nitrogen-rich diamonds (type Ib) with [100] and [111] crystal orientations. The NV centers were created by keV-He ion bombardment and subsequent annealing, and we estimate an average number of NVs per pillar to be 4300 ± 300 and 520 ± 120 for the [100] and [111] samples, respectively. Lifetime measurements of the NVs’ excited state showed two time constants with average values of τ1 ≈ 2 ns and τ2 ≈ 8 ns, which are shorter as compared to a single color center in a bulk crystal (τ ≈ 10 ns). This is probably due to a coupling between the NVs as well as due to interaction with bombardment-induced defects and substitutional nitrogen (P1 centers). Optically detected magnetic resonance measurements revealed a contrast of about 5% and average coherence and relaxation times of T2 [100] = 420 ± 40 ns, T2 [111] = 560 ± 50 ns, and T1 [100] = 162 ± 11 μs, T1 [111] = 174 ± 24 μs. These pillars could find an application for scanning probe magnetic field imaging.
The effect of formation of a periodic surface microrelief upon tension of polymeric substrates with thin hard coatings under specified conditions (the processing temperature below the glassing temperature, elongation up to 250%, elongation rate <5mm∕min) is described. The microrelief period ranges from 0.5μm up to hundreds of micrometers, its height up to 1μm. Methods are proposed to measure low values of the optical path length in media Δn∼λ and azimuthal anchoring energy of a liquid crystal on microreliefed surfaces.
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