Screen-printed Solar Cells Research Articles

Improving the efficiency and stability of screen-printed carbon-based perovskite solar cells through passivation of electron transport compact-TiO2 layer with TiCl4

Improving the efficiency and stability of screen-printed carbon-based perovskite solar cells through passivation of electron transport compact-TiO2 layer with TiCl4

Age-induced excellence with green solvents: the impact of residual solvent and post-treatments in screen-printed carbon perovskite solar cells and modules

Screen-printed perovskite devices made using green γ-valerolactone precursors are found to improve significantly following fabrication due to slow residual solvent loss over time. This is also observed in large-scale 220 cm2 modules.

Ultra-thin silicon oxide tunnel layer passivated contacts for screen-printed n-type industry solar cells

Effects of the ultra-thin silicon oxide (SiOx) on tunnel oxide passivated contact solar cells (TOPCon) are investigated in this paper. The experiment is fabricated to study the TOPCon electrical performance with different SiOx thickness and the champion efficiency is achieved by the TOPCon with a 1.5 nm SiOx layer, with Voc 698.93 mV, Jsc 40.14 mA/cm2, FF 81.03 and efficiency 22.73 %. For futher understanding, EDNA2 and AFORS-HET are used to simulate the relationship between the SiOx thickness, rear SRV and the doping concentration in n+ layer. It indicates that the total J0 at the SiOx-(c-Si) interface (J0, interface) can be affected by the phosphorus concentration at the SiOx-(c-Si) interface. Besides, due to the variation of SRV or P-doped concentration, different recombination mechanisms, including auger recombination and surface recombination, will dominant the total J0, interface. In addition, the sensitivity of TOPCon solar cells electrical performance to SiOx thickness can be affected by rear SRV, and the sensitivity of TOPCon solar cells electrical performance to rear SRV can be affected by SiOx thickness.

Detailed investigation of electrical and optical properties of textured n-type and roughened p-type tunnel oxide passivated contacts for screen-printed double-side passivated contact silicon solar cell application

This paper presents detailed characterization and analyses of the optical, electrical, and contact properties of a 35 nm phosphorus-doped (n-type) polysilicon (poly-Si) and a 250 nm boron-doped (p-type) poly-Si deposited respectively on textured and roughed surface. These layers could be applied respectively to the front and rear sides of an n-type Si to produce back junction bifacial screen-printed double-side tunnel oxide passivated contacts (DS-TOPCon) solar cells. Optical and device modeling revealed a short circuit current density loss of 1.5 mA/cm2 and 0.5 mA/cm2 due to absorption in the front n-TOPCon and rear side p-TOPCon layers, respectively. The passivation and contact properties including metalized and unmetallized recombination current density (J0), as well as contact resistivity, were determined as a function of contact firing temperature in the range of 700∼800℃. The passivation quality of the front thin n-TOPCon was found to deteriorate with increased firing temperature while the rear thick p-TOPCon improved. The study showed that the simulated contact firing at 730℃ resulted in the best unmetallized double-side TOPCon precursor, with an excellent implied open-circuit voltage of 730 mV and implied fill factor of ∼86 %. However, the metalized J0 increased and contact resistivity decreased monotonically with the increase in the firing temperature. The 2D device simulations revealed that these layers can produce screen-printed DS-TOPCon cells with an efficiency of ∼22.5 %. Solar cell modeling also showed that the DS-TOPCon solar cell efficiency can reach 24.1 % by decreasing the n-TOPCon thickness to 20 nm and lowering the full area metalized J0 to ∼100 mA/cm2.

Charge trapping and photovoltaic characteristics in monocrystalline silicon solar cells employing molybdenum oxide and copper oxide stacked hole-selective contacts

A hole-selective contact (HSC) composed of stacked layers of molybdenum oxide (MoOx) and copper oxide (CuOx), called MOCOSL, has been proposed as passivation booster for screen-printed monocrystalline silicon solar cell (SMSC) applications. The passivation quality of MOCOSL is investigated by characterizing its charge trapping properties, including fixed oxide charge (Qf) and interface trap density (Dit). The conversion efficiency (CE) of SMSCs is improved by MOCOSL, resulting in an increase from 20.66% to 21.76%. This improvement is attributed to an increase in the negative Qf and a decrease in Dit, which result in an increase in the open circuit voltage (Voc) and short circuit current (Jsc). Specifically, the number of negative Qf is increased by MOCOSL, which helps to reduce the recombination of charge carriers.

A Review of Different Types of Solar Cell Materials Employed in Bifacial Solar Photovoltaic Panel

Conventionally accessible silicon solar cells experience two major drawbacks, such as reduced efficiency and increased fabrication costs. The prospects for the reduction in the cost of the photovoltaic form of energy conversion are bifacial solar cells. Bifacial solar cells show potential opportunity in reducing the cost of solar energy conversion when analyzed with respect to monofacial cells. The bifacial solar cells exploit sunlight occurrence on both sides of the cell more efficiently. Bifacial-based solar photovoltaic (PV) is a technology that increases the generation of electrical energy per square meter of PV module through the utilization of light absorption from the albedo. This technology can generally be categorized based on the type of solar cell material and the fabrication technique. PV devices are classified as a silicon-based, thin film, organic, and advanced nano PV. This paper takes a second look at some recent initiatives and significant issues in enhancing the efficiency of bifacial solar cells from material sciences and chemical composition aspects. From this review, it is concluded that screen-printed solar cells have produced a maximum efficiency of 22%. Additionally, triode structure single-crystalline cells produced a maximum front side efficiency of 21.3% and rear side efficiency of 19.8%. Considering the recycling of solar panels, organic solar panels can be developed.

Photovoltaic and interface characteristics of mono-crystalline silicon solar cells with molybdenum oxide hole-selective layers by ammonium hydroxide reconstructed nanostructure

Ammonium hydroxide reconstructed nanostructure (AHRN) is proposed as an attachment enhancer between molybdenum oxide (MoOx) hole-selective layers (HSLs) and silicon interface for screen-printed mono-crystalline silicon solar cell (SMSC) applications. The conversion efficiency (CE) is demonstrated from 20.6% to 21.6% for SMSCs with MoO2 HSL and attachment enhancer. The betterment mechanism is attributed to a suitable nanostructure, resulting in the increase of the fill factor and peeling force. Moreover, the interface trap density (Dit) is hardly degraded by MoO2 formed on the Si surface at a specific AHRN.

Bottom-Up and Top-Down Approaches for Identifying and Mitigating Electrical Losses in Silicon Heterojunction Solar Cells

Electrical losses in silicon heterojunction (SHJ) solar cells are difficult to identify and to control as multiple material layers and several entangled physical phenomena are involved. In this context, this contribution aims to accurately investigate and characterize the electrical losses affecting the collection of photogenerated carriers in SHJ solar cells and to provide means to mitigate them. In particular, the material properties controlling the physical coupling between the n-type hydrogenated silicon and the transparent conductive oxide (TCO) layers are studied. To this aim, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">top-down</i> and the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">bottom-up</i> approaches are introduced and applied to develop different material layers and to study the final device performance once these layers are integrated inside actual solar cells. First, the bulk and interface layer properties required for an efficient carrier transport within the n-type carrier selective passivating contacts of SHJ devices are decoupled by using multilayers which combine thin n-type hydrogenated amorphous and nanocrystalline silicon layers. The multilayer characteristics yielding efficient transport are investigated for two different TCOs, which are indium-tin-oxide (ITO) and aluminium-zinc-oxide (AZO). Second, the passivation quality is studied at various process steps and the contact resistivity is investigated. Finally, these multilayers are further optimized to obtain low series resistance and high final passivation once coupled with both TCOs. As major outcomes, a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$2\times 2$</tex-math></inline-formula> -cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> screen-printed SHJ solar cell with 82.33% fill factor and 24.24% efficiency was reached using AZO as rear TCO and the best certified <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$2\times 2$</tex-math></inline-formula> -cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> solar cell integrating ITO demonstrated a fill factor of 82.28% along with an efficiency of 24.21%.

Screen-printed Hole Transport Material-free perovskite solar cell for water splitting incorporating Cu-NiCo2O4 catalyst

Water splitting has gained significant attention in recent years as a greener alternative for harvesting energy. In this report, we utilize screen-printed Hole Transport Material (HTM) free single junction perovskite solar cell with an open circuit voltage (Voc) of 0.9 V for direct water splitting. Further, we extend this concept to incorporate three different earth-abundant materials: copper, copper-nickel, and copper-nickel–cobalt oxide, as catalysts in a 1 M Potassium hydroxide (KOH) electrolyte solution, along with a perovskite solar cell for water splitting. Among these, the perovskite solar cell with a copper-nickel–cobalt oxide catalyst shows the best performance with 0.98 mA/cm2 photocurrent density and 1.2% solar to hydrogen efficiency at no applied bias, i.e., 0 V vs Reverse Hydrogen Electrode (RHE).

Physical and photovoltaic characteristics of copper oxide thin films as hole-selective layers for screen-printed mono-crystalline silicon solar cell applications

Copper oxide (CuO4.8) is proposed as a hole-selective layer (HSL) for screen-printed mono-crystalline silicon solar cell (SMSC) applications. The bandgap, work function, and valance band offset (VBO) of the CuO4.8 HSL are presented. The energy band diagram of the P-Si(100)/SiOx/CuO4.8/Ag stacked film is shown. The results indicate an improvement of the conversion efficiency of more than 1.4% absolute from 17.2% to 18.6% for SMSCs with CuO4.8 as the HSL. The promotion mechanism is attributed to the low VBO of the CuO4.8 HSL. Moreover, the surface recombination is reduced by tunneling SiOx formed on the Si surface during CuO4.8 evaporation at a specific ambient oxygen level.

Detailed loss analysis of 24.8% large-area screen-printed n-type solar cell with polysilicon passivating contact

Doped polysilicon-based passivating contacts are expected to be a key technology to enable higher efficiency in mass-produced silicon solar cells in coming years, with the world market share expected to increase almost 9-fold to 35% in 2031. The excellent carrier selectivity of passivated contacts enables low-resistance extraction of carriers without compromising surface passivation and has been instrumental in recent advances in high-efficiency solar cells. Here, we report on the application of phosphorus-doped polysilicon passivating contacts on large-area screen-printed n-type silicon solar cells, using industrially viable fabrication processes. A champion cell efficiency of 24.79% is reported, as independently measured by ISFH-CalTeC on a 163.75 × 163.75-mm solar cell. Detailed characterization and simulation are applied to investigate the primary losses and pathways for further improvement of the state-of-the-art industrial high-efficiency solar cell, revealing that the front-side boron-diffused region accounts for around 63% of the electrical losses.

Screen-printed n-type Si solar cells with laser-doped selective back surface field

The primary challenge to the industrial application of n-type silicon solar cells is relatively complicated process flow compared to producing p-type silicon solar cells. This paper demonstrates a simple processing sequence to fabricate n-type silicon solar cells in which the boron-doped emitter and phosphorus-doped back surface field (BSF) are formed in one high-temperature step. By introducing a selective BSF structure that is formed by laser doping, the conversion efficiency of the solar cells can be further improved. The averaged conversion efficiency of 21.7% is obtained in batches with relatively large quantity of cells with tight efficiency distribution.

Pathway towards 24% efficiency for fully screen-printed passivated emitter and rear contact solar cells

In this work, the efficiency potential of the fully screen-printed passivated emitter and rear contact (PERC) solar cell structure is investigated via numerical simulations. A series of improvements and optimizations are performed on bulk quality, emitter properties and metallization of screen-printed PERC solar cells based on experimental results obtained in both industry and laboratory environments. With significantly improved bulk and surface passivation quality, we find that carrier recombination losses at the metal/silicon interface will impose a substantial limitation on efficiencies, highlighting the need for developing new screen-printing technologies to overcome the limitation from contact recombination. By improving the effectiveness of the back-surface field, reducing coverage area of laser-doped selective emitters and the front metal/silicon interface contact area, a 15 mV improvement in open-circuit voltage (V OC) was achieved in our modelled cells, due to greatly reduced contact recombination losses. With the further implementation of a multi-busbar and fine-line printing technologies, efficiency above 24% was obtained from simulations. Subsequently, a comprehensive pathway towards 24% efficiency for screen-printed PERC solar cells is proposed, without the need to implement passivated contacts or transition to a plated metallisation scheme. Key target requirements for future developments are also identified.

Effects of surface morphology on Ag crystallite formation in screen-printed multi-crystalline Si solar cells

The electrode collects electrons produced by a solar cell. Ag crystallites generated during front electrode formation play an important role in transferring electrons from the emitter to the Ag finger. Previously, the formation mechanism of Ag crystallites and the various factors influencing Ag crystallite formation have been studied, including the effect of surface morphology on Ag crystallite formation. The glass coverage varies with the texture of the Si surface, and thus the degree of exposure of the Si surface varies correspondingly. When the Si surface is exposed, direct contact is achieved, and contact resistance is improved. However, the effect of surface morphology on the Ag crystallites formed on the Si surface under the glass layer has not yet been studied. The effect of surface morphology on Ag crystallite formation is presented in this work. Two multi-crystalline Si wafers with different surface morphologies were compared. The first multi-crystalline Si wafer was textured using metal-catalyzed chem ical etching (MCCE). The second multi-crystalline Si wafer was textured by MCCE followed by reactive ion etching. Wafers with sharper textures had lower series resistances, higher fill factors, and a large amount of Ag crystallites. Ag crystallites primarily formed at the tips of the texture. To analyze the effect of surface morphology, the surface electron concentration was confirmed by simulation. Electron concentration at the tip was proportional to the sharpness of the tip. Therefore, when the firing process is performed at the same temperature, wafers with sharper tips are expected to exhibit better electrode characteristics.

Direct Contact Electroplating Sequence Without Initial Seed Layer for Bifacial TOPCon Solar Cell Metallization

The metallization of bifacial tunneling oxide and passivating contacts (TOPCon) solar cells without initial metal seed layer by electroplating of Ni/Cu/Ag is demonstrated. The presented approach allows a lead-free metallization with narrow contact geometries and low contact resistivity. A metal plate provides electrical contact to the silicon via micrometer size laser contact openings and allows electroplating of bifacial TOPCon solar cells using industrial type inline plating tools without the need of a previously applied seed layer. Challenges such as direct contacting of silicon and dissolution of contacts are identified, and potential solutions are discussed. An optimized process sequence is developed and with this approach a solar cell efficiency of 22.5% is demonstrated on industrial bifacial TOPCon solar cells reaching the same level as the screen-printed reference solar cells.

Hole-Selective Front Contact Stack Enabling 24.1%-Efficient Silicon Heterojunction Solar Cells

The window-layer stack limits the efficiency of both-side-contacted silicon heterojunction solar cells. We discuss here the combination of several modifications to this stack to improve its optoelectronic performance. These include the introduction of a nanocrystalline silicon-oxide p-type layer in lieu of the amorphous silicon p-type layer, replacing indium tin oxide with a zirconium-doped indium oxide for the front transparent electrode, capping this layer with a silicon-oxide film and applying a postfabrication electrical biasing treatment. The influence of each of these alterations is discussed as well as their interactions. Combining all of them finally enables the fabrication of a highly transparent and electrically well-performing window-layer stack, leading to a screen-printed silicon heterojunction solar cell with 24.1% efficiency. Paths toward industrialization and further improvements are finally discussed.

Screen-printed n-type industry solar cells with tunnel oxide passivated contact doped by phosphorus diffusion

Abstract Tunnel oxide passivated contact (TOPCon) industrial (244.32 cm2) c-Si solar cell is fabricated in this paper. Both the ultra-thin silicon oxide layer and intrinsic polycrystalline silicon layer are deposited by low-pressure chemical vapor deposited (LPCVD). Then intrinsic polycrystalline silicon layers are doped by thermal diffusion of POCl3 in an industrial-scale quartz tube furnace. Experiment conditions like polycrystalline silicon thickness, diffusion temperature, diffusion time and POCL3 flow rate on the passivation quality of TOPCon structure are investigated in detail and low recombination current density ~8 fA/m2 has been achieved for c-Si/SiOx/poly-Si(70 nm)/SiNx structure at diffusion temperature 850 °C. A variation about 30–40 mV has been observed between the iVoc and Voc for 70 nm samples, which should be attributed to the metallization-induced degration. Not consistent with the result obtained from symmetric samples, both an improvement to the solar cell efficiency has been found for 70 nm thick poly-Si and 170 nm thick poly-Si at the diffusion temperature above the optimal diffusion temperature. Finally, by optimizing the polysilion thickness and phosphorus diffusion, the champion solar cell efficiency of 22.81% is achieved, with Voc of 702.6 mV, Jsc of 39.78 mA/cm2, FF of 81.62%.

Improving surface passivation on very thin substrates for high efficiency silicon heterojunction solar cells

Silicon solar cells are now less than 3% absolute from the theoretical efficiency limit. Advanced passivated contact architectures have demonstrated surface saturation current densities close to 1 fA/cm2. We have optimized the thin intrinsic hydrogenated amorphous silicon layer by controlling the deposition temperature and the silane-to-hydrogen dilution ratio. Thin wafers were used as a testbed to increase the sensitivity to surface passivation. By optimizing the intrinsic layer, we reduced the surface saturation current densities from 1.7 fA/cm2 to 0.6 fA/cm2 on textured wafers with thicknesses ranging between 40 and 180 μm. Implied open-circuit voltages over 760 mV were accomplished on p-i/c-Si/i-n structures deposited on n-type CZ wafers with wafer thicknesses below 50 μm. Further, we demonstrated experimentally the potential of using very thin wafers by manufacturing screen-printed silicon heterojunction solar cells on 40 μm thick standalone wafers while achieving an efficiency of 20.48%.

Finger Metallization Using Pattern Transfer Printing Technology for c-Si Solar Cell

Front metallization of crystalline silicon solar cells requires smaller finger lines in order to collect the generated current from the active area efficiently. Pattern transfer printing (PTP) technology enables finger widths down to 20 μm and aspect ratios above 0.6 using thick film silver paste. This work investigates the influence of PTP process parameters, i.e., laser power and trench geometry, on the finger geometry and the print quality. Silver fingers obtained from four different trench geometries were analyzed and the electrical parameters of corresponding printed solar cells were compared with standard screen-printed solar cells. We observed a strong dependence of the finger aspect ratio and the amount of debris on the laser power that was used during the transfer process. Each trench geometry requires a different laser power, which is related to the ratio between the circumference and the horizontal interface of the trench. Despite a modest FF loss due to higher series resistance, a significant gain in Jsc and a smaller gain in Voc increased the cell efficiency by 0.12%abs for the best group of PTP-printed cells compared with the reference screen-printed cells. Importantly, the amount of silver required was reduced by 54% compared with the screen-printed reference.

Fully screen-printed bifacial large area 22.6% N-type Si solar cell with lightly doped ion-implanted boron emitter and tunnel oxide passivated rear contact

We report on the fabrication of fully screen-printed bifacial large area (239 cm2) high-efficiency n-type Si solar cells with ion-implanted homogeneous boron emitter on the front side and carrier-selective tunnel oxide passivated contact (TOPCon) on the rear. Our phosphorus-doped poly-Si/SiOx passivated contact with SiNx capping layer gave excellent surface passivation with a very low recombination current density (J0_TOPCon) of ~1 fA/cm2 after a simulated firing treatment at ~770 °C without metallization. After screen-printed and fire-through metallization on n-TOPCon with ~13% metal coverage, metallized J0_TOPCon value increased to only ~5 fA/cm2. In addition, homogenous boron implanted emitter (~180 Ω/) passivated with ALD Al2O3 layer capped with PECVD SiNx/SiOx double-layer antireflection (DLAR) coating gave excellent passivation with emitter recombination current density of ~12 fA/cm2 prior to metallization. The industrial screen-printed, fire-through contacts with floating busbars on this boron emitter gave metallized emitter recombination current density of ~31 fA/cm2. This resulted in a low-cost industrial screen-printed n-type bifacial Si solar cell with 22.6% efficiency and 702 mV open-circuit voltage (Voc).