Baojie Yan

Bio: Baojie Yan is an academic researcher from Chinese Academy of Sciences. The author has contributed to research in topics: Nanocrystalline silicon & Silicon. The author has an hindex of 28, co-authored 227 publications receiving 3067 citations. Previous affiliations of Baojie Yan include University of Utah & Nankai University.

Innovative dual function nc-SiOx:H layer leading to a >16% efficient multi-junction thin-film silicon solar cell

Abstract: We present our development of n-type nano-structured hydrogenated silicon oxide (nc-SiOx:H) as a dual-function layer in multi-junction solar cells. We optimized nc-SiOx:H and attained a conductivity suitable for a doped layer and optical property suitable for an inter-reflection layer. We tested the effectiveness of the dual-function nc-SiOx:H layer by replacing the normal n layer between the middle and the bottom cells in an a-Si:H/a-SiGe:H/nc-Si:H triple-junction structure. A significant gain in the middle cell current density of ∼1.0 mA/cm2 is achieved. We further optimized the component cells and the triple-junction structures and attained an initial active-area cell efficiency of 16.3%.

Optimization of back reflector for high efficiency hydrogenated nanocrystalline silicon solar cells

Abstract: We have studied the effect of texture in Ag/ZnO back reflectors (BRs) on the performance of hydrogenated nanocrystalline silicon (nc-Si:H) solar cells. While a larger texture provides superior light trapping, it also deteriorates the nc-Si:H quality. We have used total and diffused reflection and atomic force microscopy to evaluate the BR texture. A BR with textured Ag and thin ZnO layers has been found to give the best cell performance. Using the optimized BR, we have achieved an initial active-area efficiency of 10.2% in a nc-Si:H single-junction cell and a stable total-area efficiency of 12.5% in a hydrogenated amorphous silicon/nc-Si:H/nc-Si:H triple-junction cell.

Hydrogen dilution profiling for hydrogenated microcrystalline silicon solar cells

Abstract: The structural properties of hydrogenated microcrystalline silicon solar cells are investigated using Raman, x-ray diffraction, and atomic force microscopy. The experimental results showed a significant increase of microcrystalline volume fraction and grain size with increasing film thickness. The correlation between the cell performance and the microstructure suggests that the increase of grain size and microcrystalline volume fraction with thickness is the main reason for the deterioration of cell performance as the intrinsic layer thickness increases. By varying the hydrogen dilution in the gas mixture during deposition, microstructure evolution has been controlled and cell performance significantly improved.

Light-induced metastability in hydrogenated nanocrystalline silicon solar cells

Abstract: Light-induced metastability in hydrogenated nanocrystalline silicon (nc-Si:H) single-junction solar cells has been studied under different light spectra. The nc-Si:H studied contains a certain fraction of hydrogenated amorphous silicon (a-Si:H). We observe no light-induced degradation when the photon energy used is lower than the bandgap of a-Si:H, while degradation occurs when the photon energy is higher than the bandgap. We conclude that the light-induced defect generation occurs mainly in the amorphous phase. Light soaking experiments on a-Si:H∕a-SiGe:H∕nc-Si:H triple-junction solar cells show no light-induced degradation in the bottom cell, because the a-Si:H top and a a-SiGe:H middle cells absorb most of the high-energy photons.

Diamond-like amorphous carbon

Abstract: 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).

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

Abstract: 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.

Stability of polymer solar cells.

Abstract: 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.