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[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Diamond-like carbon (DLC) is a metastable form of amorphous carbon with significant sp3 bonding. DLC is a semiconductor with a high mechanical hardness, chemical inertness, and optical transparency. This review will describe the deposition methods, deposition mechanisms, characterisation methods, electronic structure, gap states, defects, doping, luminescence, field emission, mechanical properties and some applications of DLCs. The films have widespread applications as protective coatings in areas, such as magnetic storage disks, optical windows and micro-electromechanical devices (MEMs).

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Diamond-like amorphous carbon

The ionic defects at the surfaces and grain boundaries of organic–inorganic halide perovskite films are detrimental to both the efficiency and stability of perovskite solar cells. Here, we show that quaternary ammonium halides can effectively passivate ionic defects in several different types of hybrid perovskite with their negative- and positive-charged components. The efficient defect passivation reduces the charge trap density and elongates the carrier recombination lifetime, which is supported by density-function-theory calculation. The defect passivation reduces the open-circuit-voltage deficit of the p–i–n-structured device to 0.39 V, and boosts the efficiency to a certified value of 20.59 ± 0.45%. Moreover, the defect healing also significantly enhances the stability of films in ambient conditions. Our findings provide an avenue for defect passivation to further improve both the efficiency and stability of solar cells. Losses in solar cells can be caused by material defects in the bulk or at interfaces. Here, Zheng et al. use quaternary ammonium halides to passivate various perovskite absorbers and prepare solar cells with certified efficiency above 20%, suggesting that both anionic and cation defects are affected.

https://par.nsf.gov/servlets/purl/10056130

Defect passivation in hybrid perovskite solar cells using quaternary ammonium halide anions and cations

Organic photovoltaics (OPVs) evolve in an exponential manner in the two key areas of efficiency and stability. The power conversion efficiency (PCE) has in the last decade been increased by almost a factor of ten approaching 10%. A main concern has been the stability that was previously measured in minutes, but can now, in favorable circumstances, exceed many thousands of hours. This astonishing achievement is the subject of this article, which reviews the developments in stability/degradation of OPVs in the last five years. This progress has been gained by several developments, such as inverted device structures of the bulk heterojunction geometry device, which allows for more stable metal electrodes, the choice of more photostable active materials, the introduction of interfacial layers, and roll-to-roll fabrication, which promises fast and cheap production methods while creating its own challenges in terms of stability.

Stability of polymer solar cells.

Hydrogenated microcrystalline silicon (μc-Si:H) solar cells are made using modified veryhigh-frequency (MVHF) glow discharge at deposition rates ∼3-5 A/s. We find that the solar cells made under certain conditions show degradation in air without intentional light soaking. The short-circuit current drops significantly within a few days after deposition, and then stabilizes. We believe that post-deposition oxygen diffusion along the grain boundaries or cracks is the origin of the ambient degradation. By optimizing the deposition conditions, we have found a plasma regime in which the μc-Si:H solar cells do not show such ambient degradation. The best a-Si:H/μc-Si:H double-junction solar cell has an initial active-area efficiency of 10.9% and is stable against the ambient degradation. The stability data of the solar cells after light soaking are also presented.

Hydrogenated Microcrystalline Silicon Solar Cells Made with Modified Very-High-Frequency Glow Discharge

Temperature-dependent distributions of activation energies in amorphous semiconductors

Small-angle neutron scattering (SANS) is used to search for nonuniform H distributions in hydrogenated amorphous silicon, a-Si:H. Thin films about 2-\ensuremath{\mu}m-thick grown with and without D substitution for H by plasma-enhanced chemical vapor deposition show both large (g20 nm) and small (8 nm) heterogeneous features. The absolute SANS intensities, however, are small and place stringent upper limits on the degree of H heterogeneity present. These results do not support a recently proposed two-domain, amorphous/paracrystalline model. The presence of a small amount of microcrystallinity yields much stronger SANS intensities, consistent with H accumulation in grain boundary regions and/or enhanced microvoid formation. A clear correlation of the larger scattering features with film surface roughness is found.

Nonuniform H distribution in thin-film hydrogenated amorphous Si by small-angle neutron scattering

Amorphous silicon/crystal silicon heterojunction double-junction tandem solar cell with open-circuit voltage above 1.5 V and high short-circuit current density

Amorphous and nanocrystalline Zinc Oxynitride (nc-ZnON) has been found to be one kind of potential materials for thin film transistors in the application of advanced display because of their high carrier mobility and low persistent photocurrent. We report a systematic study of ZnON properties and their correlation to the deposition conditions in a reactive sputtering process using a metallic Zn target in a gas mixture of Ar, N2 and O2. The most sensitive parameter to the material properties is O2 and N2 flow rates. At given N2 and Ar flow rates, the ZnON materials show polycrystalline ZnO properties when a relatively high O2 flow rate is used; become a mixture of ZnO and Zn3N2 with a nanocrystalline structure when a medium O2 flow rate is used; and finally show polycrystalline Zn3N2 properties when a small or no O2 flow rate is used. The RF power also shows a strong influence on the material properties. At a given gas mixture, a low RF power produces polycrystalline ZnO-like materials and a high power pro...

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Baojie Yan

Papers

Hydrogenated Microcrystalline Silicon Solar Cells Made with Modified Very-High-Frequency Glow Discharge

Temperature-dependent distributions of activation energies in amorphous semiconductors

Nonuniform H distribution in thin-film hydrogenated amorphous Si by small-angle neutron scattering

Amorphous silicon/crystal silicon heterojunction double-junction tandem solar cell with open-circuit voltage above 1.5 V and high short-circuit current density

The correlation of material properties and deposition condition of ZnON thin films