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Mallem, Kumar,Kim, Yong Jun,Hussain, Shahzada Qamar,Dutta, Subhajit,Le, Anh Huy Tuan,Ju, Minkyu,Park, Jinjoo,Cho, Young Hyun,Kim, Youngkuk,Cho, Eun-Chel,Yi, Junsin Elsevier 2019 Materials research bulletin Vol.110 No.-
<P><B>Abstract</B></P> <P>Transition metal oxides (TMO) are extensively applied as a surface passivation and carrier-selective contact layer through replacing boron/phosphorus doped emitter layers in silicon heterojunction (SHJ) solar cell applications. In this regard, molybdenum oxide (MoO<SUB>3</SUB>) has drawn a significant attention as a hole extraction layer owing properties such as wide bandgap (∼3 eV), high work function (>6 eV) and low temperature deposition. Thus, we fabricated SHJ solar cells with a dopant-free MoO<SUB>x</SUB> applied at the front surface contact layer. Thermally evaporated MoO<SUB>x</SUB> films were exhibited optical characteristics such as high transmittance, high bandgap and low absorption coefficient as compared to a-Si:H(p) and μc-SiO<SUB>x</SUB>:H (p) layers. X-ray photoelectron spectroscopy (XPS) analysis confirmed the stoichiometric and oxidation deficiency states of the of the MoO<SUB>x</SUB> layers. Whereas, MoO<SUB>x</SUB> films undergoing long-term air exposure showed an increase in Mo<SUP>5+</SUP> cations due to the increased oxygen vacancy. The fabricated MoO<SUB>x</SUB>/c-Si heterojunction solar cells achieved a significant power conversion efficiency (η) of 20%, best open circuit voltage (V<SUB>oc</SUB>) of 695 mV, high short circuit current density (J<SUB>sc</SUB>) of 38.88 mA/cm<SUP>2</SUP> and a fill factor (FF) of 74.0%. These results implying that MoO<SUB>x</SUB> is as an excellent dopant-free material for alternate p-doped a-Si:H emitter layers in SHJ solar cell applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> MoO<SUB>x</SUB> layer was used to fabricate high efficiency of Si heterojunction solar cells. </LI> <LI> MoO<SUB>x</SUB> layers exhibited high transmittance, bandgap and low absorption coefficient. </LI> <LI> XPS analysis confirmed the stoichiometric analysis of MoO<SUB>x</SUB> films. </LI> <LI> Thickness and ambient annealing effect on the MoO<SUB>x</SUB>/Si was strictly investigated. </LI> <LI> 20.0% improved cell efficiency was achieved for MoO<SUB>x</SUB>/Si heterojunction solar cells. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
High-efficiency Crystalline Silicon Solar Cells: A Review
Sanchari Chowdhury,Mallem Kumar,DUTTA SUBHAJIT,박진수,김재민,김세현,주민규,김영국,조영현,조은철,이준신 한국신·재생에너지학회 2019 신재생에너지 Vol.15 No.3
Solar energy is a clean renewable energy resource that can be converted to electricity with photovoltaic (PV) technology without environmental damage. Solar energy can be transformed to electricity using a range of technologies, but crystalline silicon (c-Si)-based PV technology dominates in the PV market due to the high efficiency, long-term stability, reliability, and second most abundant (27%) material. Recently, c-Si solar cells achieved an outstanding efficiency of 26.7% through silicon heterojunction technology combined with an interdigitated back contact structure. Most industries and researchers are attempting to improve the efficiency further to reach the silicon limit. The dominant position of crystalline silicon solar cell in large-area electricity production and industrialization motivated us to write this review paper. This review paper covers the key factors that affect the efficiency, such as structure, process optimization, cost reduction strategies. In addition, some promising cell structures, such as Passivated Emitter Rear Contact (PERC) solar cell, Interdigitated Back Contact (IBC) solar cell, Heterojunction Intrinsic Thin Layer (HIT) solar cell, and Heterojunction Back Contact (HBC) solar cell, and their efficiencies are reported. Overall, this study provides a detailed idea to the new photovoltaic researchers regarding the solar cell structure, their efficiencies, and future potential of solar cells.
Ju, Minkyu,Mallem, Kumar,Dutta, Subhajit,Balaji, Nagarajan,Oh, Donghyun,Cho, Eun-Chel,Cho, Young Hyun,Kim, Youngkuk,Yi, Junsin Elsevier 2018 Materials science in semiconductor processing Vol.85 No.-
<P><B>Abstract</B></P> <P>Front side textured random pyramids are widely utilized in major industries for the performance enhancement of crystalline silicon (c-Si) solar cells. Random pyramids not only reduce the surface reflectance but also improve the light trapping effect. Therefore, it is necessary to understand the pyramid height affecting the cell performance, further improving cell efficiency. In this work, we present an experimental study to investigate the influence of pyramids size on the contact shading loss mechanism of silver (Ag) screen-printed p-type c-Si solar cells. Three alkaline texture solutions with sodium silicate additives were optimized to develop the small pyramid (0.5–2.0 µm) size, middle pyramid (5.0–9.0 µm) size and large pyramid (10–15 µm) size on the c-Si surface, respectively. It was noticed that screen-printed finger width strongly depends on pyramid size. Even though, same mesh patterns and screen printing conditions resulted in 20 µm widening of metal finger width on the large pyramids as compared to the small pyramids. This was attributed to the increase in the size of cell surface pyramids that not only varied the gap between the screen mesh and cell surface while screen-printing but also hindered the contraction of metal electrodes during the firing process. The c-Si solar cells with large pyramids suffered from an extra shading loss during fabrication, thus, led to the reduction of the short circuit current density (~0.7 mA/cm<SUP>2</SUP>) resulting in lower efficiency (~17.72%) as compared to efficiency (~18.60%) of small pyramid based cells.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Random textured pyramid size effect on the Ag-printed Si solar cells is investigated. </LI> <LI> Anisotropic etching and pyramid size was controlled with NaOH-IPA additive of Na<SUB>2</SUB>SiO<SUB>3</SUB>. </LI> <LI> Improved performance of small pyramid archived of ~0.7 mA/cm<SUP>2</SUP> higher than large pyramid. </LI> <LI> Textured pyramid height and figure contact roughness was confirmed by SEM images. </LI> <LI> Contact widening and shading loss analysis of small to large pyramid cells are studied. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Electrical Loss Reduction in Crystalline Silicon Photovoltaic Module Assembly: A Review
Sanchari Chowdhury,Mallem Kumar,Minkyu Ju,Youngkuk Kim,Chang-Soon Han,Jinshu Park,Jaimin Kim,Young Hyun Cho,Eun-Chel Cho,Junsin Yi 한국태양광발전학회 2019 Current Photovoltaic Research Vol.7 No.4
The output power of a crystalline silicon (c-Si) photovoltaic (PV) module is not directly the sum of the powers of its unit cells. There are several losses and gain mechanisms that reduce the total output power when solar cells are encapsulated into solar modules. Theses factors are getting high attention as the high cell efficiency achievement become more complex and expensive. More research works are involved to minimize the “cell-to-module” (CTM) loss. Our paper is aimed to focus on electrical losses due to interconnection and mismatch loss at PV modules. Research study shows that among all reasons of PV module failure 40.7% fails at interconnection. The mismatch loss in modern PV modules is very low (nearly 0.1%) but still lacks in the approach that determines all the contributing factors in mismatch loss. This review paper is related to study of interconnection loss technologies and key factors contributing to mismatch loss during module fabrication. Also, the improved interconnection technologies, understanding the approaches to mitigate the mismatch loss factors are precisely described here. This research study will give the approach of mitigating the loss and enable improvement in reliability of PV modules.