n-Si bifacial concentrator solar cell (original) (raw)
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Bifacial concentrator Ag-free crystalline n-type Si solar cell
Progress in Photovoltaics: Research and Applications, 2014
We report results obtained using an innovative approach for the fabrication of bifacial low-concentrator thin Ag-free n-type Cz-Si (Czochralski silicon) solar cells based on an indium tin oxide/(p + nn +)Cz-Si/indium fluorine oxide structure. The (p + nn +)Cz-Si structure was produced by boron and phosphorus diffusion from Band P-containing glasses deposited on the opposite sides of n-type Cz-Si wafers, followed by an etch-back step. Transparent conducting oxide (TCO) films, acting as antireflection electrodes, were deposited by ultrasonic spray pyrolysis on both sides. A copper wire contact pattern was attached by low-temperature (160°C) lamination simultaneously to the front and rear transparent conducting oxide layers as well as to the interconnecting ribbons located outside the structure. The shadowing from the contacts was~4%. The resulting solar cells, 25 × 25 mm 2 in dimensions, showed front/rear efficiencies of 17.6-17.9%/16.7-17.0%, respectively, at one to three suns (bifaciality of~95%). Even at one-sun front illumination and 20-50% one-sun rear illumination, such a cell will generate energy approaching that produced by a monofacial solar cell of 21-26% efficiency.
Results obtained in frame of an innovative approach for fabrication of the bifacial low concentrator Ag free Cz silicon solar cells based on Indium-Tin-Oxide(ITO)/(p + nn +)Cz-Si/Indium-Fluorine-Oxide (IFO) structure (n-type cell) as well as on IFO/(n + pp +)Cz-Si/ITO structure (p-type cell) are presented in this work. The (p + nn +)Cz-Si and (n + pp +)Cz-Si structures were produced by diffusion of boron and phosphorus from deposited Band P-containing glasses followed by an etch-back step. The n + surface of the structures was textured, whereas the p + surface remained planar. Transparent conducting oxide (TCO) films, which act as passivating and antireflection electrodes, were deposited by ultrasonic spray pyrolysis method on both sides. The contact pattern of copper wire was attached by the low-temperature (160 °C) lamination method simultaneously to the front and rear TCO layers as well as to the interconnecting ribbons arranged outside the structure. The shadowing from the contacts is in the range of ~4%. The resulting solar cells showed front/rear efficiencies
Results regarding bifacial silicon solar cells with external busbars are presented. The cells consist of [n+p(n)p+]Cz-Si structures with a current-collecting system of new design: a laminated grid of wire external busbars (LGWEB). A LGWEB consists of a transparent conducting oxide film deposited onto a Si structure, busbars adjacent to the Si structure, and a contact wire grid attached simultaneously to the oxide and busbars using the low-temperature lamination method. Bifacial LGWEB solar cells demonstrate record high efficiency for similar devices: 17.7% (n-Si)/17.3% (p-Si) with 74–82% bifaciality for the smooth back surface and 16.3% (n-Si)/16.4%(p-Si) with 89% bifaciality for the textured back surface. It is shown that the LGWEB technologycan provide an efficiency exceeding 21%.
15th International Conference on Concentrator Photovoltaic Systems (CPV-15), 2019
We present Ag-free low-concentrator bifacial indium-fluorine-oxide (IFO)/(n + pp +)Cz-Si/indium-tin-oxide (ITO) solar cells based on: (i) a shallow phosphorus-doped n +-emitter; (ii) an easy-to-fabricate screen-printed Al-alloyed Al-p + back-surface-field (BSF); (iii) transparent conductive IFO and ITO layers grown by ultrasonic spray pyrolysis, which act as passivating and antireflection electrode; (iv) Ag-free multi-wire metallization of copper wire attached by the low-temperature lamination method simultaneously to the front IFO layer, rear ITO layer as well as to the interconnecting ribbons arranged outside the structure using transparent conductive polymer films. For the manufacture of solar cells, we used standard commercially available SiNx/(n + pp +)Cz-Si/Al structures. After removal of the residual Al paste, the Al-p + layer was thinned by one-sided etchback process. A number of solar cells were prepared differing in the sheet resistance of the Al-p + layer (Rp+), which ranged from 14 Ω/sq (original, non-etched Al-p + layer) to 123 Ω/sq. It was found that thinning of the Al-p + layer (increase in Rp+) greatly improved all the parameters of solar cells. The cell with Rp+ = 81 Ω/sq showed the best combination of conversion parameters. Under 1-sun front/rear illumination, the conversion efficiency of this cell is 17.5%/11.2% (against 16.0%/7.5% for the cell with Rp+ = 14 Ω/sq). At 1-sun front illumination and 20/50% albedo of 1-sun illumination, the equivalent efficiency is equal to 19.9%/23.5% (against 17.7%/20.1% for the cell with Rp+ = 14 Ω/sq). At a sunlight concentration ratio (kC) of 2.3-2.7 suns, the cells with Rp+ in the range 45-123 Ω/sq showed approximately similar maximum front-side efficiency, 17.5-17.9%. However, the operating range of sunlight concentration ratio (kC,OR) determined as η(kC,OR) = η(kC = 1) showed a tendency to decrease from 5.8 ± 0.6 suns to 4 ± 0.5 suns with an increase in Rp+ from 14-45 Ω/sq to 63-123 Ω/sq.
AIP Conference Proceedings, 2017
Replacing expensive silver with inexpensive copper for the metallization of silicon wafer solar cells can lead to substantial reductions in material costs associated with cell production. A promising approach is the use of multi-wire design. This technology uses many wires in the place of busbars, and the copper wires are "soldered" during the lowtemperature lamination process to the fingers (printed or plated) or to the transparent conductive oxide (TCO) layer, e.g. in the case of the-Si/c-Si heterojunction cells. Here we describe a solar cell design in which wires are attached to TCO layers using transparent conductive polymer (TCP) films. To this end, we have synthesized a number of thermoplastics, poly(arylene ether ketone) copolymers (co-PAEKs), containing phthalide in their main chain. The fraction of phthalidecontaining units in the copolymers was p = 3, 5, 15, and 50 mol %. With increasing p, the peak strain temperature of the co-PAEKs rises from 205 to 290 C and their optical band gap and refractive index increase from 3.12 to 3.15 eV and from 1.6 to 1.614, respectively. The copolymers have a negligible absorption coefficient in the wavelength range 400-1100 nm. When exposed to an excess pressure of 1 atm or above, co-PAEK films less than 30 μm in thickness undergo a transition from a dielectric to a conductive state. The resistivity () of wire/TCP/TCO (ITO = In 2 O 3 :Sn and IFO = In 2 O 3 :F) contacts ranges from 0.37 to 1.43 m cm 2. The polymer with the highest phthalide content (p = 50 mol %) has the lowest. The average work of adhesion per unit area determined by pulling off the wires from the polymer surface depends on both the phthalide content of the co-PAEKs and their reduced viscosity, ranging from 14.3 to 43.5 N/cm. The highest value was obtained for the co-PAEK with p = 50 mol %. We have fabricated low-concentration bifacial IFO/(n + pp +)Cz-Si/ITO solar cells with a wire contact grid attached to IFO and ITO using a co-PAEK film. The efficiency of the best cell under 1× to 7× front/rear illumination was determined to be 18.3-18.9%/15.0-15.6%.
Towards bifacial silicon heterojunction solar cells with reduced TCO use
Progress in Photovoltaics: Research and Applications, 2022
Reducing indium consumption, which is related to the transparent conductive oxide (TCO) use, is a key challenge for scaling up silicon heterojunction (SHJ) solar cell technology to terawatt level. In this work, we developed bifacial SHJ solar cells with reduced TCO thickness. We present three types of In 2 O 3-based TCOs, tin-, fluorine-, and tungsten-doped In 2 O 3 (ITO, IFO, and IWO), whose thickness has been optimally minimized. These are promising TCOs, respectively, from post-transition metal doping, anionic doping, and transition metal doping and exhibit different opto-electrical properties. We performed optical simulations and electrical investigations with varied TCO thicknesses. The results indicate that (i) reducing TCO thickness could yield larger current in both monofacial and bifacial SHJ devices; (ii) our IWO and IFO are favorable for n-contact and p-contact, respectively; and (iii) our ITO could serve well for both ncontact and p-contact. Interestingly, for the p-contact, with the ITO thickness reducing from 75 nm to 25 nm, the average contact resistivity values show a decreasing trend from 390 mΩ cm 2 to 114 mΩ cm 2. With applying 25-nm-thick front IWO in n-contact, and 25-nm-thick rear ITO use in p-contact, we obtained front side efficiencies above 22% in bifacial SHJ solar cells. This represents a 67% TCO reduction with respect to a reference bifacial solar cell with 75-nm-thick TCO on both sides.
In order to compensate the insufficient conductance of heterojunction thin films, transparent conductive oxides (TCO) have been used for decades in both-sides contacted crystalline silicon heterojunction (SHJ) solar cells to provide lateral conduction for efficient carrier collection. In this work, we substitute the TCO layers by utilizing the lateral conduction of c-Si absorber, thereby enabling a TCO-free design. A series resistance of 0.32 Ωcm2 and a fill factor of 80.7% were measured for a TCO-free back-junction SHJ solar cell with a conventional finger pitch of 1.8 mm, thereby proving that relying on lateral conduction in the c-Si bulk is compatible with low series resistances. Achieving high efficiencies in SHJ solar cells with TCO-free front contacts requires suppressing deterioration of the passivation quality induced by direct metal-a-Si:H contacts and in-diffusion of metal into the a-Si:H layer. We show that an ozone treatment at the a-Si:H/metal interface suppresses the m...
Silicon nitride passivated bifacial Cz-silicon solar cells
Solar Energy Materials and Solar Cells, 2009
A new process for all silicon nitride passivated silicon solar cells with screen printed contacts is analysed in detail. Since the contacts are fired through the silicon nitride layers on both sides, the process is easy to adapt to industrial production. The potential and limits of the presented bifacial design are simulated and discussed. The effectiveness of the presented process depends strongly on the base doping of the substrate, but only the open circuit voltage is affected. The current is mainly determined by the rear surface passivation properties. Thus, using a low resistivity ðo1:5 O cmÞ base material higher efficiencies compared to an aluminium back surface field can be achieved.
Highly Efficient Bifacial Silicon/Silicon Tandem Solar Cells
IEEE Access
Silicon-based tandem solar cells with efficient use of the solar spectrum are desirable for a next generation-commercial photovoltaic system. It has been widely investigated elsewhere using perovskites or III-V cells as top cell materials for high efficiency and stability. However, perovskite and III-V top cells are still unsuitable for mass production as well as expansion and integration with silicon solar cell production processes so far. Two-terminal bifacial Si/Si tandem cell by bonding with transparent conductive adhesive (TCA) is reported here. The current matching can maximize the efficiency by controlling the opening area of the top cell, which makes the bottom cell also able to absorb sunlight in the short wavelength region that is absorbed by the top cell as well, without being limited to the thickness or bandgap of the top cell. The Si/Si tandem solar cell achieved short circuit current density of 25.195 mA/cm 2 after current matching by 36% opening ratio of top cell. INDEX TERMS Tandem solar cell, two-terminal, silicon solar cell, transparent conductive adhesive (TCA), current matching.
Solar Energy Materials and Solar Cells, 2013
The front transparent conductive oxide layer is a source of significant optical and electrical losses in silicon heterojunction solar cells because of the trade-off between free-carrier absorption and sheet resistance. We demonstrate that hydrogen-doped indium oxide (IO:H), which has an electron mobility of over 100 cm 2 /V s, reduces these losses compared to traditional, low-mobility transparent conductive oxides, but suffers from high contact resistance at the interface of the IO:H layer and the silver front electrode grid. This problem is avoided by inserting a thin indium tin oxide (ITO) layer at the IO:H/silver interface. Such IO:H/ITO bilayers have low contact resistance, sheet resistance, and free-carrier absorption, and outperform IO:H-only or ITO-only layers in solar cells. We report a certified efficiency of 22.1% for a 4-cm 2 screen-printed silicon heterojunction solar cell employing an IO:H/ITO bilayer as the front transparent conductive oxide.