Search

Recently, the charge carrier transport mechanism of passivating contacts, which feature an ultra-thin oxide layer, has been investigated by studying temperature-dependent current-voltage ( I-V ) characteristics. The measurement revealed that tunneling is the dominant transport path for tunnel oxide passivated contact (TOPCon) with wet chemically grown oxide layer. Furthermore, higher annealing temperatures led to the deterioration of the surface passivation most likely because of excessive pinhole formation. In this contribution, we are going to extend the previous study by analyzing other interfacial oxides as well. We will show that extremely low recombination current densities and low contact resistivity values can be achieved by differently processed TOPCon structures, which are characterized by a predominant tunnel transport as well as one where current flow via pinholes likely predominates. Furthermore, an I-V ( T ) study on solar cells with passivating rear contact reveals that fill factor transitions from a nonlinear to linear behavior when the Si layer turns partially crystalline.

Hidrojenlendirilmiş nano / mikro kristal silisyum (nc-/c-Si:H) ince film malzemeler, Silisyum tabanlı ince film güneş gözeleri teknolojisinin anahtar malzemesidir. Bu filmler ince film güneş gözeleri uygulamalarında kullanılması nedeniyle yüksek oranda ilgi çekmektedir. Özellikle birbiri ardına dizilmiş çoklu Silisyum tabanlı ince film güneş gözeleri uygulamaları için silisyumun amorf fazdan nano / mikro kristal faza geçişi incelenmesi gereken önemli bir süreçtir. Böyle bir faz diyagramı oluşturmak malzemelerin ve göze yapılarının geliştirilmesinde kullanılacak fazların belirlenmesini mümkün kılacaktır. Bu çalışma kapsamında plazma ortamında kimyasal buhar biriktirme, magnetron saçtırma ve elektron demeti buharlaştırma gibi farklı yöntemlerle üretilen amorf silisyum ince film malzemesinin kristalleşme dinamikleri incelenmiştir. Bu birbirlerinden farklı yöntemlerin uygun maliyetliliği, film homojenliği, birikinti hızı ve uygulanabilirliği gibi özellikleri göz önünde bulundurularak birbirlerine göre avantajları ve dezavantajları araştırılmıştır. Her bir teknik için birikinti gücü, basıncı, kaplama süresi, alt taş sıcaklığı ve kullanılan besleme gazinin seyreltilme miktarı gibi parametreler ayrıntılı bir biçimde incelenmiştir. Büyütülen filmlerin yapısal, biçimsel, ışıksal ve elektriksel özellikleri analiz edilmiştir. Silisyum ince filmler cam, kuartz ve silisyum dilimlerin üzerine büyütülmüş olup Raman Spektroskopisi (RS), X-Işını Kırınımı (GIXRD), X-Işını Foto elektron Spektroskopisi (XPS), Ellipsometer (SE), Fourier Dönüşümlü Kızılötesi Spektroskopisi (FTIR), Taramalı Elektron Mikroskopu (SEM), Yüksek Kontrastlı Transmisyon Elektron Mikroskopu (HRTEM) gibi analiz metotlarıyla kontrol edilmiştir. Bu çalışmada Raman Spektroskopi analizinden hesaplanan kristal hacim fraksiyonu yapısal geçişi göstermede ana parametre olarak kabul edilmiştir. Bu araştırmanın sonunda, farklı fiziksel ve kimyasal buhar biriktirme metotları için kristalleşme parametreleri hakkında ayrıntılı ve güvenilir bilgi edinilmiştir. Hydrogenated nano/micro-cystalline silicon (nc-/c-Si:H) thin films are the key materials for Si-based thin film solar cell technology. These films have attracted great attention due to their applications in thin film solar cells. Silicon phase transition from amorphous to nano/micro-crystalline phase is an important phenomenon, especially in progress of Si thin film tandem structured solar cells. It is well-accepted fact that the development of deposition phase diagrams allows phase engineering for systematic improvement of materials and cell structures. In this thesis, crystallization dynamics of the amorphous silicon prepared via different deposition techniques such as magnetron sputtering, electron beam evaporation, CCP-assisted CVD and ICP-assisted CVD have been investigated. The advantages and disadvantages of these production methods have been debated by considering different aspects such as cost efficiency, film uniformity, deposition rate and applicability. For each technique, different deposition parameters such as deposition power, pressure, coating duration, substrate temperature, and source gas dilution were investigated comprehensively. Deposited films were analyzed in structural, morphological, optical and electrical features. Films are deposited on different substrate such as glass, quartz and Si-wafer and basic diagnostic tools like Raman Spectroscopy (RS), Grazing Incidence X-Ray Diffraction (GR-XRD), X-Ray Photoelectron Spectroscopy (XPS), Spectroscopic Ellipsometry (SE), Fourier Transform Infra-Red Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), High Resolution Transmission Electron Microscopy (HRTEM) are used as complementary methods. Crystalline volume fraction calculated by RS is assumed as the key parameter while defining the structural transition. At the end of this research, general knowledge about the crystallization parameters for different chemical and physical vapor deposition techniques was obtained. 117

Today more than 90% of the global PV market is covered by c-Si solar cells which are limited by recombination losses at the metal-semiconductor interface. This recombination path can be avoided by separating the metal from the c-Si wafer by introducing a buffer layer that passivates electronically the wafer surface while still allowing the flow of one type of carrier. Such structures are called carrier selective passivating contacts. In the scope of this thesis, carrier selective passivating contacts with low and high thermal budgets are investigated with the purpose of achieving a good understanding of the junction formation, the working principle, limiting factors, and integration requirements. Silicon heterojunction (SHJ) solar cells are studied as representatives for solar cells processed with low thermal budget. Solar cells with interfacial oxide contacts are investigated as the cell concept for high thermal budgets. To be industrially relevant, contact formation of the latter is studied with p-type wafers. The carrier selective passivating contacts based on microcrystalline silicon (mc-Si:H) are studied for SHJ solar cells with low thermal budget. It is demonstrated that mc-Si:H layers improve the optical and electrical performance of the SHJ solar cells compared to cells with purely amorphous contacts. However, as the layer crystallinity increases with thickness, a trade¿off between short circuit current density and fill factor is encountered. By combining a MoOx front hole-contact and a mc-Si:H(n) rear electron-contact, this trade¿off is avoided. Applying an electrodeposited copper front metallization, a short circuit current density of 38.9 mA/cm2 and a fill factor of to 80% are obtained leading to an efficiency of 22.5%. The passivating hole contacts with high thermal budget are developed using a chemically grown oxide (SiOx) and boron doped silicon-carbide which is deposited under Si-rich conditions by plasma enhanced chemical vapour deposition. It is observed that introducing an undoped Si inter¿layer between SiOx and SiCx(p) is necessary to prevent chemical reaction between carbon atoms in the SiCx(p) and the adjacent SiOx, and consequently to obtain wellpassivated SiOx/c-Si interface. With this contact structure, an implied open circuit voltage value of 718 mV and a specific contact resistivity value of 17m­ cm2 are attained. The contact structure is tested at device level by realizing proof-of-concept hybrid solar cells that feature a high thermal budget rear hole-contact and a low thermal budget SHJ front electron-contact. With this concept, the fill factor of 81.8% is attained. In an effort to improve the hole-contact property further, in-situ incorporation of fluorine into the boron-doped hole-contact is explored. It is observed that in the as-deposited state, fluorine is evenly distributed within the contact layer of SiCx:F(p). Upon annealing, fluorine diffuses toward the c-Si wafer and accumulates at the interface where it reduces the defect states. With this contact structure, implied open circuit voltage values up to 735mV are achieved. The potential of the fluorinated hole-contact is investigated at device level by realizing both sides-contacted co-processed solar. For this purpose in-situ phosphorous doped SiCx(n) layers were developed as a front contact. Planar, both sides-contacted p-type solar cells attain an impressive fill factor value of 84% and an open circuit voltage of 727 mV.

We present electron- and hole-selective passivating contacts based on wet-chemically grown interfacial SiOx and overlying in-situ doped silicon carbide (SiCx) deposited by plasma-enhanced chemical vapor deposition. After annealing at 850 degrees C, excellent surface passivation on the p-type planar crystalline silicon wafer is obtained for both electron- and hole-selective contacts. Their potential is demonstrated at the device level by employing a simple process flow, in which the junction formation of the two polarities is achieved with a single coannealing step. Both-side-contacted patterning-free planar p-type cells with an area of 4 cm(2) and screen-printed metallization reach a fill factor of 83.4% and a open-circuit voltage of 726 mV. Zirconium-doped indium oxide with excellent optoelectrical properties is used as a front electrode. The decrease in the parasitic absorption in the front electrode results in higher photogenerated current. By realizing front-side-textured and rear-side-planar p-type cells, an efficiency of up to 22.6% is achieved.

The present invention relates to a solar cell comprising a heterojunction photoelectric device comprising, a front electrode layer, a back electrode layer comprising a metallic contact layer (300), a light-absorbing silicon layer (1 ) arranged between said front electrode and said back electrode layers and a doped silicon-based layer (6) arranged between said light-absorbing silicon layer (1 ) and said back electrode layer, characterized in that said heterojunction photoelectric device further comprises a wide band gap material layer (10) having an electronic band gap greater than 1.4eV, said wide band gap material layer being applied on a surface of the light- absorbing silicon layer (1 ) between said light-absorbing silicon layer and said doped silicon-based layer (6). The present heterojunction layer or stack of layers is compatible with thermal annealing and firing processes at T above 600 °C.

We present a p-type passivating rear contact that complies with integration into standard solar cell manufacturing with phosphorus-diffused front side. Our contact structure consists of a thin SiOx tunneling layer grown by wet chemistry and a stack of layers deposited in one single run by plasma-enhanced chemical vapor deposition. The layers of the stack were tailored to protect the interfacial oxide layer, to act as a source for boron diffusion into the wafer and to connect to the external metallisation with low contact resistivity. We found that this stack tolerated annealing at 900 degrees C over a wide range of dwell times: for 15 min anneals we obtained dark saturation current densities (J(o)) as low as 10 fA center dot cm(-2) (after hydrogenation) and after 12-fold increase of the annealing time to 180 min, J(0) was only increased to 12 fA center dot cm(-2). These values corresponded to implied open circuit voltages (iV(oc)) of 718 and 715 mV, respectively. To test passivating rear contacts under realistic operation conditions, we combined them with an n-type heterojunction into hybrid solar cells. With conversion efficiencies abovementioned 22% and V-oc > 705 mV, these devices demonstrated high level of rear surface passivation. Finally, we demonstrated the integration of the hole selective rear contact with a POCl3 diffusion process. To this end, we added a phosphorus diffusion barrier to our layer stack by depositing one additional layer of amorphous SiOx on top of the stack. For symmetric samples with this layer structure on both sides, we observed iV(oc) values of 714 and 712 mV on n- and p-type silicon wafers after hydrogenation, respectively. Co-diffused cells with POCl3 front diffused emitter and rear passivating contact resulted so far in efficiencies of 20.4% and 20.1% for n- and p-type wafers, respectively.

Intrinsic amorphous silicon provides excellent surface passivation on crystalline silicon. It has previously been shown, that carriers that are photo generated in the amorphous silicon can be efficiently electronically injected into the crystalline silicon. A method to quantify the efficiency of such carrier injection using the spectral response of photoluminescence has recently been demonstrated. This is a contactless method and it can be applied to incomplete device structures. Here we use this technique to measure partially processed hetero-junction devices with different capping layers to quantify their impact on the carrier injection efficiency. Silicon nitride capping on amorphous silicon is shown to have minimum impact on the high carrier injection efficiency of the amorphous layer but doped amorphous capping layer on the other hand were seen to have a strong effect on the carrier injection efficiency. A model was developed to understand the material properties of the amorphous layer. The reduction in carrier injection efficiency with doped amorphous silicon capping layers were attributed to the large defects in the doped layer.

The EU crystalline silicon (c-Si) PV manufacturing industry has faced strong foreign competition in the last decade. To strive in this competitive environment and differentiate itself from the competition, the EU c-Si PV manufacturing industry needs to (1) focus on highly performing c-Si PV technologies, (2) include sustainability by design, and (3) develop differentiated PV module designs for a broad range of PV applications to tap into rapidly growing existing and new markets. This is precisely the aim of the 3.5 years long H2020 funded HighLite project, which started in October 2019 under the work program LC-SC3-RES-15-2019: Increase the competitiveness of the EU PV manufacturing industry. To achieve this goal, the HighLite project focuses on bringing two advanced PV module designs and the related manufacturing solutions to higher technology readiness levels (TRL). The first module design aims to combine the benefits of n-type silicon heterojunction (SHJ) cells (high efficiency and bifaciality potential, improved sustainability, rapidly growing supply chain in the EU) with the ones of shingle assembly (higher packing density, improved modularity, and excellent aesthetics). The second module design is based on the assembly of low-cost industrial interdigitated back-contact (IBC) cells cut in half or smaller, which is interesting to improve module efficiencies and increase modularity (key for application in buildings, vehicles, etc.). This contribution provides an overview of the key results achieved so far by the HighLite project partners and discusses their relevance to help raise the EU PV industries' competitiveness. We report on promising high-efficiency industrial cell results (24.1% SHJ cell with a shingle layout and 23.9% IBC cell with passivated contacts), novel approaches for high-throughput laser cutting and edge re-passivation, module designs for BAPV, BIPV, and VIPV applications passing extended testing, and first 1-year outdoor monitoring results compared with benchmark products. This project has received funding from the European Union's Horizon 2020 Programme for research, technological development, and demonstration under Grant Agreement no. 857793.

Passivating contacts consisting of heavily doped polycrystalline silicon (poly-Si) and ultrathin interfacial silicon oxide (SiOx) films enable the fabrication of high-efficiency Si solar cells. The electrical properties and working mechanism of such poly-Si passivating contacts depend on the distribution of dopants at their interface with the underlying Si substrate of solar cells. Therefore, this distribution, particularly in the vicinity of pinholes in the SiOx film, is investigated in this work. Technology computer-aided design (TCAD) simulations were performed to study the diffusion of dopants, both phosphorus (P) and boron (B), from the poly-Si film into the Si substrate during the annealing process typically applied to poly-Si passivating contacts. The simulated 2D doping profiles indicate enhanced diffusion under pinholes, yielding deeper semicircular regions of increased doping compared to regions far removed from the pinholes. Such regions with locally enhanced doping were also experimentally demonstrated using high-resolution (5-10 nm/pixel) scanning spreading resistance microscopy (SSRM) for the first time. The SSRM measurements were performed on a variety of poly-Si passivating contacts, fabricated using different approaches by multiple research institutes, and the regions of doping enhancement were detected on samples where the presence of pinholes had been reported in the related literature. These findings can contribute to a better understanding, more accurate modeling, and optimization of poly-Si passivating contacts, which are increasingly being introduced in the mass production of Si solar cells. This work was supported by the European Union’s Horizon2020 Programme for research, technological development, and demonstration [Grant 857793] and by the Kuwait Foundation for the Advancement of Sciences [Grant CN18- 15EE-01].

Multiscale self-assembly is ubiquitous in nature but its deliberate use to synthesize multifunctional three-dimensional materials remains rare, partly due to the notoriously difficult problem of controlling topology from atomic to macroscopic scales to obtain intended material properties. Here, we propose a simple, modular, noncolloidal methodology that is based on exploiting universality in stochastic growth dynamics and driving the growth process under far-from-equilibrium conditions toward a preplanned structure. As proof of principle, we demonstrate a confined-but-connected solid structure, comprising an anisotropic random network of silicon quantum-dots that hierarchically self-assembles from the atomic to the microscopic scales. First, quantum-dots form to subsequently interconnect without inflating their diameters to form a random network, and this network then grows in a preferential direction to form undulated and branching nanowire-like structures. This specific topology simultaneously achieves two scale-dependent features, which were previously thought to be mutually exclusive: good electrical conduction on the microscale and a bandgap tunable over a range of energies on the nanoscale. © 2016 American Chemical Society.