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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.

Effect of impurities on performance of hydrogenated nanocrystalline silicon solar cells

A semiconductor device of p-i-n type configuration includes a p layer which is comprised of a p-doped semiconductor material, an n layer comprised of an n-doped semiconductor material and an i layer comprised of a substantially intrinsic, nanocrystalline semiconductor material interposed therebetween. The crystalline volume in the i layer decreases as the thickness of said layer increases from its interface with the n layer to its interface with the p layer. The grain size of the substantially intrinsic nanocrystalline semiconductor material may also decrease as the thickness of the i layer increases from its interface with the n layer to its interface with the p layer. The volume of regions of intermediate range order in a portion of the i layer commencing at the interface of the i layer and the p layer, and comprising no more than 50% of the thickness thereof, is greater than is the volume of regions of intermediate range order in the remainder of the i layer. Devices of this type may be used as photovoltaic devices, and may be fabricated by a plasma deposition process.

Stabilized photovoltaic device and methods for its manufacture

We present a systematic analysis of the correlation of current mismatch in a-Si:H/nc-Si:H double-junction solar cell fill factor (FF) measured under colored lights. First, we propose a diagnostic method to evaluate the FFs of component cells in multi-junction solar cells using current-voltage measurements under colored lights. The analysis reveals that the over-estimated FF when a colored light is illuminated results from a significant current mismatch. A mathematical calculation demonstrates that the diagnostic method can be used to estimate the FFs of single-junction component cells in a multi-junction structure. Second, we present our recent progress in the optimization of a-Si:H and nc-Si:H based solar cells. We emphasize the importance of improving the compactness of nc-Si:H materials and controlling the nanocrystalline evolution. Finally, we report our new record initial active-area efficiency of 15.4% achieved using an a-Si:H/a-SiGe:H/nc-Si:H triple-junction structure.

Correlation of current mismatch and fill factor in amorphous and nanocrystalline silicon based high efficiency multi-junction solar cells

For semi-transparent perovskite solar cells (PSCs), the bombardment during the deposition of a transparent conductive oxide would inevitably damage the underlying soft materials, thereby inducing a high density of defects and creating an unfavorable band mismatch at the interface. Although interfacial buffer layers can be adopted to alleviate this bombardment damage, the device performance is still limited by the inferior fill factor (FF) due to the increased series resistance and the decreased carrier collection. In this work, a charge transfer induced 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP):Ag complex is employed to mediate the electrical contact between a C60 electron-transport layer and sputtered indium-zinc oxide (IZO) top electrode. We demonstrate that the multifunctional BCP:Ag complex can (1) reduce the electron extraction barrier by pulling up the Fermi level of BCP, (2) create beneficial gap states for electron transport, (3) serve as a hole blocking layer to suppress charge recombination, and (4) protect the C60 underlayer from the sputtering damage. As a result, the optimized electrical contact at the C60/BCP:Ag/IZO interface significantly recovered the FF of the inverted semi-transparent perovskite solar cell from 71.8% to 80.1%, yielding a device efficiency of 18.19%. By using a 23.19% efficient silicon solar cell, we also demonstrate a four-terminal tandem configuration with a total efficiency of 27.59%.

Charge-transfer induced multifunctional BCP:Ag complexes for semi-transparent perovskite solar cells with a record fill factor of 80.1%

Amorphous and nanocrystalline thin-film silicon solar cells have been receiving a great deal of attention because of low material cost and compatibility with large-area deposition. There has been an announcement of addition of more than 2000 MW of new photovoltaic manufacturing capacity to be completed in the next 5 years using this technology. Significant progress is also being made in our understanding of these materials and devices. In this review, we discuss the methods for depositing the thin films, the material, and device properties and describe the various manufacturing methods. The products and market trends are also discussed.

Baojie Yan

Papers

Effect of impurities on performance of hydrogenated nanocrystalline silicon solar cells

Stabilized photovoltaic device and methods for its manufacture

Correlation of current mismatch and fill factor in amorphous and nanocrystalline silicon based high efficiency multi-junction solar cells

Charge-transfer induced multifunctional BCP:Ag complexes for semi-transparent perovskite solar cells with a record fill factor of 80.1%

Amorphous and Nanocrystalline Silicon Solar Cells and Modules