Interest in silicon heterojunction solar cells is growing due to their manufacturing simplicity and record efficiencies. However, a significant limitation of these devices still stems from parasitic ...light absorption in the amorphous silicon layers. This can be mitigated by replacing the traditional (p) and (n) doped amorphous silicon selective layers by other materials. While promising results have been achieved using molybdenum oxide (MoOx) as a front-side hole-selective layer, charge transport mechanisms in that contact stack have remained elusive and device efficiencies below predictions. We carefully analyze the influence of the MoOx and intrinsic a-Si:H thicknesses on current-voltage properties and discuss transport and performance-loss mechanisms. In particular, we find that thinning down the MoOx and (i)a-Si:H layers (down to 4 nm and 6 nm respectively) mitigates parasitic sub-bandgap MoOx optical absorption and drastically enhances charge transport, while still providing excellent passivation and selectivity. High-resolution transmission microscopy reveals that such thin MoOx layer remains continuous and, while slightly sub-stoechiometric, exhibits a chemistry close to MoO3. A screen-printed device reaching a certified efficiency of 23.5% and a fill factor of 81.8% is demonstrated, bridging the gap with traditional Si-based contacts and demonstrating that dopant-free selective contacts can rival traditional approaches.
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•Silicon heterojunction solar cell with ultra-thin MoOx-based contact was processed.•To better understand this contact, thickness of both MoOx and (i)a-Si:H was varied.•Current-voltage and optical properties were analyzed to discuss loss mechanisms.•Microstructural STEM and EELS analysis was carried out to check MoOx film properties.•A 23.5%-efficient device with 81.8% FF was achieved.
•Growth of methyl ammonium tin iodide (MASnI3) perovskite thin films.•Plasma enhanced chemical vapour deposition technique is used for MASnI3 thin film deposition.•Single step vacuum based approach ...for MASnI3 perovskite thin film growth.•Formation of MASnI3/Si heterojunctions.•Applications of MASnI3/silicon heterojunction as photodetector.
In the present work, lead free methyl ammonium tin iodide (CH3NH3SnI3 or MASnI3) perovskite thin films have been deposited via single step plasma enhanced chemical vapour deposition (PECVD) technique. In our earlier work, we reported lead based methyl ammonium lead iodide (CH3NH3PbI3 or MAPbI3) perovskite thin film deposition in 2-step, using sputtering technique for the PbI2 thin films and PECVD technique for CH3NH3I (MAI) thin films. Similarly, CH3NH3SnI3 perovskite thin films are deposited in this work using PECVD technique in single step. Lead is substituted with tin due to its toxic behaviour, environmental and health related issues. CH3NH3SnI3 perovskite is doped n-type via changing the molar ratio of SnI2 and CH3NH3I. SnI2/CH3NH3I ratio is changed from 0.33 to 2 to study the n-type doping of CH3NH3SnI3 perovskite. Deposited CH3NH3SnI3 perovskite thin films are deposited over p-type silicon wafer to make n-type doped n-CH3NH3SnI3/p-Si heterojunction photodiode.
The crystalline silicon heterojunction structure adopted in photovoltaic modules commercialized as Panasonic's HIT has significantly reduced recombination loss, resulting in greater conversion ...efficiency. The structure of an interdigitated back contact was adopted with our crystalline silicon heterojunction solar cells to reduce optical loss from a front grid electrode, a transparent conducting oxide (TCO) layer, and a-Si:H layers as an approach for exceeding the conversion efficiency of 25%. As a result of the improved short-circuit current (J sc ), we achieved the world's highest efficiency of 25.6% for crystalline silicon-based solar cells under 1-sun illumination (designated area: 143.7 cm 2 ).
Due to their high efficiencies combined with simple and cost-effective device fabrication, perovskite solar cells are promising candidates as top cells in tandem devices. For this application, the ...perovskite solar cell must be highly transparent at near-infrared wavelengths such that sufficient light is transmitted to the narrow-bandgap bottom cell. We demonstrate perovskite solar cells featuring a sputtered amorphous indium zinc oxide (IZO) layer as broadband transparent rear electrode. This electrode absorbs less than 3% in the 400–1200nm wavelength range, while having a sheet resistance of 35Ω/sq. We show over 9% efficient semitransparent perovskite solar cells with IZO sputtered directly on the sensitive organic charge transport layer. The efficiency can be raised up to 10.3% by inserting a thin molybdenum oxide buffer layer, mitigating sputter damage to the underlying organic layer. These cells show more than 60% average transmittance in the 800–1200nm wavelength range, which makes them suitable top-cell candidates for tandem devices. Finally, we discuss the performance potential of this highly transparent rear electrode for four-terminal tandem devices.
•We show semitransparent perovskite cell with above 10% efficiency.•We use sputtering to make a broadband transparent rear electrode.•Low carrier density/high mobility amorphous IZO without post-deposition treatment.•We study sputter damage and side-illumination effect on cell performance.•Four-terminal tandem application on silicon heterojunction solar cell.
Improving power conversion efficiency (PCE) in photovoltaics has driven innovative approaches in solar cell design and technology. Silicon heterojunction (SHJ) solar cells exhibit advantages in PCE ...due to their effective passivating contact structures. SHJ–interdigitated back contact (SHJ–IBC) solar cells have the potential to surpass traditional SHJ cells, attributed to their advantage in short‐circuit current (JSC). Herein, Silvaco Atlas technology computer‐aided design is used to create digital twins of high‐efficiency SHJ solar cells with amorphous silicon and nanocrystalline silicon hole selective contact (HSC) layers. Using parameters from digital twins of SHJ solar cells, the practical efficiency limit of SHJ–IBC solar cells is assessed. The results show that SHJ–IBC cells can achieve potential efficiencies of 27.01% with amorphous HSC and 27.38% with nanocrystalline HSC. Further efficiency augmentation to 27.51% can be achieved by narrowing the gap from 80 to 20 μm. This study not only advances comprehension of SHJ–IBC solar cells but also provides insights into optimizing geometrical configurations for improved performance. The utilization of digital twins provides a valuable tool for predicting and evaluating the performance of SHJ–IBC solar cells, contributing substantively to the ongoing development of high‐efficiency photovoltaic technology.
A digital twin is a virtual version of a physical object in its digital environment. It benefits from having real‐time data, which make it considerably richer for study. Herein, the practical efficiency limit of silicon heterojunction–interdigitated back contact solar cells is evaluated through the creation of digital twins.
Here we report a certified efficiency of up to 25.11% for silicon heterojunction (SHJ) solar cells on a full size n-type M2 monocrystalline-silicon (c-Si) wafer (total area, 244.5 cm2). An ultra-thin ...intrinsic a-Si:H buffer layer was introduced on the c-Si wafer surface using a 13.56 MHz home-made RF-PECVD with low deposition rate showing superior surface passivation. The ultra-thin i-a-Si:H film with both higher microstructure factor (R*) and H content evidently increases the SHJ solar cell open-circuit voltage (VOC) by 2 mV, and moreover, short-circuit current (ISC) and fill factor (FF) are also notably improved, resulting in a 0.52% absolute cell efficiency enhancement, in which FF is the main cause. In order to explore high conversion efficiency SHJ solar cells, both home-made RF-PECVD and commercial VHF-PECVD (40.68 MHz) are employed for deposition of the i-a-Si:H passivation layer. As a result, the efficiency of RF-PECVD-prepared SHJ cell is 0.21% higher than that of VHF-PECVD-prepared, mainly driven by VOC and ISC boost. This work offers a useful tool for fabrication of high performance SHJ solar cells which could be employed in mass production.
•25.11% high efficiency silicon heterojunction solar cells on a full size n-type M2 c-Si wafer is obtained.•An ultra-thin intrinsic a-Si:H buffer layer with low deposition rate shows superior surface passivation.•The ultra-thin i-a-Si:H film has both a higher microstructure factor (R*) and H content.•The efficiency of RF-PECVD-prepared SHJ cell is 0.21% higher than that of VHF-PECVD-prepared.
This work reports on a comparative study comprising three transition metal oxides, MoO3, WO3 and V2O5, acting as front p-type contacts for n-type crystalline silicon heterojunction solar cells. Owing ...to their high work functions (>5eV) and wide energy band gaps, these oxides act as transparent hole-selective contacts with semiconductive properties that are determined by oxygen-vacancy defects (MoO3−x), as confirmed by X-ray photoelectron spectroscopy. In the fabricated hybrid structures, 15nm thick transition metal oxide layers were deposited by vacuum thermal evaporation. Of all three devices, the V2O5/n-silicon heterojunction performed the best with a conversion efficiency of 15.7% and an open-circuit voltage of 606mV, followed by MoO3 (13.6%) and WO3 (12.5%). These results bring into view a new silicon heterojunction solar cell concept with advantages such as the absence of toxic dopant gases and a simplified low-temperature fabrication process.
•Transition metal oxide/n-crystalline silicon solar cells were fabricated.•V2Ox, MoOx and WOx were obtained after thermal evaporation under vacuum.•XPS analyses revealed the presence of oxygen vacancies and/or gap states.•Highest efficiency (open-circuit voltage) was 15.7% (606mV) for V2Ox/silicon.•Current-voltage response is limited by diffusion of injected minority carriers.
•H3PO4 is used to modify the ITO surface for obtaining better wettability and higher work function.•The gird on the H3PO4-treated ITO is pinhole-free and more uniform.•After H3PO4 treatment, the ...contact resistivity between the electroplated grid and ITO is significantly reduced from 1.5 mΩ·cm2 to 0.4 mΩ·cm2.•The proof-of-concept SCs with H3PO4-treated ITO receives a champion power conversion efficiency of 23.19%.
Electroplating technology is considered as a promising alternative to low-temperature sintered silver pastes for the purpose of significantly reducing the cost of silicon heterojunction (SHJ) solar cells (SCs). However, achieving excellent contact quality between the plated grid and indium tin oxide (ITO) remains a big challenge to satisfy the requirements for fabrication and high performance. In this work, phosphoric acid (H3PO4) is used to modify the ITO surface to improve the contact quality of the plated grid/ITO and enhance the performance of SHJ SCs. It is found that the phosphate groups are adsorbed on the ITO surface to form a dipole layer after H3PO4 treatment. The wettability of H3PO4-treated ITO is substantially improved, resulting in a pinhole-free electroplated nickel (Ni) seed layer. Moreover, the work function of ITO rises by approximately 0.2 eV, which reduces the contact potential barrier between the ITO and the metal electrode. The contact resistivity (ρc) between the plated grid and H3PO4-treated ITO is reduced to approximately 0.4 mΩ·cm2, compared to 1.5 mΩ·cm2 of the control sample. In addition, the metal grid formed on the H3PO4-treated ITO exhibits a better uniformity. Finally, the SHJ cell with H3PO4 treatment process receives a remarkable power conversion efficiency (PCE) of 23.19%, which is approximately 1% (absolute) higher than that of the control device. Therefore, we demonstrate that modifying ITO by H3PO4 is a promising way to improve the contact quality for the electroplating metallization in SHJ SCs.
We review the recent progress of silicon heterojunction (SHJ) solar cells. Recently, a new efficiency world record for silicon solar cells of 26.7% has been set by Kaneka Corp. using this technology. ...This was mainly achieved by remarkably increasing the fill-factor (FF) to 84.9% - the highest FF published for a silicon solar cell to date. High FF have for long been a challenge for SHJ technology. We emphasize with the help of simulations the importance of minimised recombination, not only to reach high open-circuit voltages, but also high FF, and discuss the most important loss mechanisms. We review the different cell-to-module loss and gain mechanisms putting focus on those that impact FF. With respect to industrialization of SHJ technology, we discuss the current hindrances and possible solutions, of which many are already present in industry. With the intrinsic bifacial nature of SHJ technology as well as its low temperature coefficient record high energy production per rated power is achievable in many climate regions.
•Review of recent progress in SHJ technology.•Simulations of bulk and surface recombination underline importance of passivation for high FF.•Discussion of module & industrial aspects of SHJ technology.
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