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Electrical and optical properties of Si microwire solar cells
Kim, Hong-Sik,Patel, Dipal B.,Kim, Hyunyub,Patel, Malkeshkumar,Chauhan, Khushbu R.,Park, Wanghee,Kim, Joondong North-Holland 2017 Solar Energy Materials and Solar Cells Vol. No.
<P><B>Abstract</B></P> <P>A record-high efficiency of 16.92% was realized by using microscale-patterned Si solar cells. Si microwire (SiMW) solar cells were designed to compare their performances with the standard flat-Si solar cell. The diameter and period of SiMWs were tuned to investigate the effects on the operation and the electrical properties of the solar cells. The highest efficiency SiMW solar cell has a width of 1.57µm to provide the significantly enhanced efficiency of 16.92% from 10.15% of the flat-Si solar cell, due to the improved values of open circuit voltage (608mV), short circuit current density (36.47mA/cm<SUP>2</SUP>) and fill factor (76.29%). Impedance spectroscopy and capacitance-voltage studies were carried out to obtain series and shunt resistances, built-in potential, acceptor carrier density, depletion width and flat band potential. Optical properties of SiMW solar cells were analyzed by external and internal quantum efficiencies. The carrier lifetime was measured by using open circuit voltage decay technique. Systematic analyses were performed to reveal the optical and electrical features of SiMW solar cells. These findings may provide efficient design schemes for high-performing solar cells using structured platforms.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Various geometries were given for Si microwire (SiMW) solar cells. </LI> <LI> The effect of minority carrier lifetime was investigated. </LI> <LI> Depletion width and recombination probability is a function of geometry. </LI> <LI> Diameter design is pivotal to collect carriers for enhanced performance. </LI> </UL> </P>
Surface-concentrated light and efficient carrier collection in microhole-patterned Si solar cells.
Kim, Joondong,Lee, Eunsongyi,Ju, Minkyu,Kim, Hyunyub,Yi, Junsin,Moon, Sang-Jin,Hyun, Moon Seop,Kim, Dong-Wook Optical Society of America 2013 Optics express Vol.21 No.4
<P>We investigate photovoltaic characteristics of crystalline Si solar cells with microhole-patterned surface. We compare patterned samples with different hole-widths and periods with a planar counterpart. From the finite-difference time-domain simulation, the patterned and planar samples are expected to have similar short circuit current density, J(sc) (difference: 1.2%). In contrast, the difference in the measured J(sc) is as large as 12.6%. The simulated optical field patterns reveal that the sample with more significantly concentrated light near the surface has higher quantum efficiency due to more efficient carrier collection. We report the highest efficiency of 15.6% among the hole-patterned solar cells.</P>
Optimization of transparent conductor-embedding front electrodes for efficient light management
Mingeon Kim,김준동,Hyunyub Kim,Jaewoo Choi,Jinjoo Park,Min Cheol Ahn,이준신 한국물리학회 2013 Current Applied Physics Vol.13 No.5
An optically and electrically optimum designed front electrode is reported by using a transparent conductive oxide (TCO) film integration. A substantial enhancement of light absorption was achieved by reduction of silver (Ag) grid shading losses while holding a similar series resistance. This obviously improves the solar cell efficiency with a significant reduction in the use of Ag shading area by one fourth. Due to the optical and electrical excellent indium-tin-oxide (ITO), the TCO benefits to widen the light transparent surface and spontaneously works as an anti-reflection coating layer. We have demonstrated that a trade-off between the optical and the electrical aspects should be considered to transfer the optical benefit by ITO supporting transparent electrode to the practical electrical advantage of current enhancement. Transmission line method was applied to profile the variation of contact resistances and specific contact resistance for optimum design of ITO-integrated front electrodes.
Routes for realizing high-performing Si solar cells by using periodic structures
Yadav, Pankaj,Patel, Malkeshkumar,Kim, Hyunyub,Cho, Yunae,Kim, Hyunki,Kim, Joondong,Yi, Junsin,Kim, Dong-Wook Elsevier 2017 Materials research bulletin Vol.94 No.-
<P><B>Abstract</B></P> <P>Theoretical suggestion indicated the substantial improvement of solar cells by using periodic structures. Yet, the promise has not been practically realized due to the lack of electrical analyses of periodical light-absorbing structure. Here, we report the record high-efficiency of 16.9% for periodically patterned silicon (Si) solar cells. Periodic Si micro-pillars were fabricated for large-scale solar cells. The Si pillars with a height of about 5μm provided significantly enlarged light-active surface, which improved the photo-generated carrier collection efficiency. From optical aspects, the pillar structures reduced light reflection and hence effectively drove more photons into the absorber layer. Additionally, the enhanced pillar-structured Si surface definitely contributed to reduce an electrical resistance of a solar cell. We demonstrated that the surficial enhanced Si design could be a promising approach for high-efficient solar cell applications. We may suggest a route for the optimum electrical designs of periodic structured solar cells.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The record high-efficiency of 16.9% for periodically patterned Si solar cells. </LI> <LI> Optical and electrical benefits of periodic microscale Si structures. </LI> <LI> Design routes for realizing high-performing periodic Si solar cells. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>