Daniel Amkreutz

Helmholtz-Zentrum Berlin | HZB · Institute for Silicon Photovoltaics

Electrically detected magnetic resonance (EDMR) is a spectroscopic technique that provides information about the physical properties of materials through the detection of variations in conductivity induced by spin-dependent processes. EDMR has been widely applied to investigate thin-film semiconductor materials in which the presence of defects can...

Reflection losses and soiling of photovoltaic devices are well-known challenges that suppress their full operational potential. Multifunctional self-cleaning light management foils offer a concurrent solution to both subjects. Here we demonstrate a simple processing method to fabricate a lotus leaf textured fluoropolymer foil by nanoimprint lithogr...

The thermal stability of thick (∽4 µm) hydrogenated amorphous silicon (a‐Si:H) layers on glass upon application of a rather rapid annealing step is investigated. Such films are of interest as precursor layers for laser liquid phase crystallized silicon solar cells. However, at least half‐day annealing at T ≈ 550 °C is considered to be necessary so...

Liquid phase crystallized silicon solar cells on glass have recently demonstrated 15.1% efficiency using a heterojunction interdigitated back contact cell architecture and an absorber thickness of 14 μm. One of the key enabling developments was a new method to first passivate electron contact fingers with a-Si:H(i) and then locally laser fire them...

A bottom‐up approach to creating silicon solar cells has the potential to not only avoid kerflosses incurred in wafer slicing, but also the energy involved in kerfless slicing techniques. Liquid‐phase‐crystallized silicon (LPC‐Si) is one such approach in which amorphous/nanocrystalline silicon is deposited on glass up to a desired thickness (5‐40 μ...

Liquid phase crystallized silicon (LPC-Si) solar cells on glass have demonstrated 14.2% efficiency using a heterojunction interdigitated back contact cell architecture and an absorber thickness of 13 μm. However, losses are incurred in charge collection under the majority carrier contact regions even after reducing their width to 60−120 μm. Recentl...

Free access till 05.12.19 on the following link: https://authors.elsevier.com/a/1ZvK13In-93NjQ . This work reports a laser firing technique applied to completed silicon heterojunction interdigitated back contact solar cells in order to lower contact resistance. Previously, the implementation of a-Si:H(i) at the electron contact of polycrystalline...

The implementation of light management textures in thin-film solar cells often simultaneously causes an undesired deterioration of electronic performance. Here, we introduce a simple yet effective technique for improved light management in liquid phase crystallized silicon thin-film solar cells on glass. By imprinting pyramidal textures on the sun-...

Combining the emerging perovskite solar cell technology with existing silicon approaches in a tandem cell design offers the possibility for new low-cost high-performance devices. In this study, the potential of liquid phase crystallized silicon (LPC-Si) solar cells as a bottom cell in an all-thin-film tandem device is investigated. By optimizing th...

en Electron beam evaporation of silicon High rate electron beam evaporation of silicon is a versatile technique to deposit silicon layers with tailored properties on large areas in a cost effective manner. A unique feature of the process is the wide range of deposition rates that can be selected. This technique allows for the deposition of nanomete...

This paper reports on the electrical quality of liquid phase crystallized silicon (LPC-Si) on glass for thin-film solar cell applications. Spatially resolved methods such as light beam induced current (LBIC), microwave photoconductance decay (MWPCD) mapping, and electron backscatter diffraction were used to access the overall material quality, intr...

Silicon nitride (SiNx) and silicon oxide (SiOx) grown with plasma‐enhanced chemical vapor deposition are used to passivate the front‐side of liquid‐phase crystallized silicon (LPC‐Si). The dielectric layer/LPC‐Si interface is smooth and layers are well‐defined as demonstrated with transmission electron microscopy. Using electron energy loss spectro...

Liquid phase crystallization of silicon (LPC-Si) offers great potential for high-quality Si films and a cost effective fabrication technique for thin crystalline silicon solar cells on glass. In this work, we report on the progress on LPC-silicon at HZB in the past years. Beginning with a brief description of the fabrication process, we summarize t...

Liquid phase crystallization of silicon (LPC-Si) on glass is a promising method to produce high quality multi-crystalline Si films with macroscopic grains. In this study, we report on recent improvements of our interdigitated back-contact silicon heterojunction contact system (IBC-SHJ), which enabled open circuit voltages as high as 661 mV and effi...

Liquid-phase crystallization (LPC) of thin silicon layers on glass substrates is a technique to fabricate solar cells with low energy and material consumption and open-circuit voltages comparable to multicrystalline silicon wafer cells. We studied the impact of different passivation layers deposited with plasma-enhanced chemical vapor deposition (P...

Liquid phase crystallized silicon on glass with a thickness of (10-40) μm has the potential to reduce material costs and the environmental impact of crystalline silicon solar cells. Recently, wafer quality open circuit voltages of over 650 mV and remarkable photocurrent densities of over 30 mA/cm² have been demonstrated on this material, however, a...

Liquid phase crystallization using line-shaped energy sources such as CW-diode lasers or electron beams has proven to form mc-Si layers on borosilicate or borosilicate/aluminosilicate glass that exhibit wafer equivalent grain sizes and electronic quality. In this work, we characterize the impact of the employed dielectric interlayer stack sandwiche...

In this paper, we report on the current status of absorber attributes in Liquid Phase Crystallized Silicon (LPC-Si) cells. To this end, an absorber doping series (N D = 2·10¹⁶/cm³ to 7·10¹⁷/cm³) and an absorber thickness variation (14 and 33μm) are evaluated. Best cells from the batches for these series showed open circuit voltages up to 640mV and...

Recently, liquid phase crystallization of thin silicon films has emerged as a candidate for thin-film photovoltaics. On 10 μm thin absorbers, wafer-equivalent morphologies and open-circuit voltages were reached, leading to 13.2% record efficiency. However, short-circuit current densities are still limited, mainly due to optical losses at the glass-...

Liquid-phase crystallization (LPC) of silicon is a suitable method to grow large grained poly-crystalline silicon with wafer equivalent electronic quality on cheap glass substrates. Dielectric layers between glass and silicon (called interlayer) are not only crucial for the solar cell performance, but, they also provide wetting of the silicon durin...

Crystalline silicon (c-Si) thin film technology is one technology that offers a significant potential with regards to material and energy and, therefore, cost-cutting and is in line with predicted industry trends. This chapter focuses on the preparation and the properties of solar cells based on thin liquid-phase crystallized Si absorbers. In the p...

The passivation quality at the interface between liquid-phase crystallized silicon (LPC-Si) and a dielectric interlayer (IL) was investigated in terms of the defect state density at the IL/LPC-Si interface (Dit) as well as the effective fixed charge density in the IL (QIL,eff). Both parameters were obtained via high-frequency capacitance–voltage me...

A major limitation in current liquid-phase crystallized (LPC) silicon thin-film record solar cells is optical losses caused by their planar glass-silicon interface. In this study, silicon is grown on nanoimprinted periodically, as well as randomly textured glass substrates, and successfully implemented into state-of-the-art LPC silicon thin-film so...

We develop a method to quantify the local minority carrier diffusion lengths in interdigitated back-contact solar cells having a 10-µm-thick liquid-phase crystallized (LPC) Si absorber by light-beam induced current (LBIC) measurements. The method is verified by 2-D simulations of the LBIC signals using ASPIN3. The effective minority carrier diffusi...

Liquid phase crystallization has emerged as a novel approach to grow large grained polycrystalline silicon films on glass with high electronic quality. In recent years a lot of effort was conducted by different groups to determine and optimize suitable interlayer materials, enhance the crystallographic quality or to improve post crystallization tre...

The charge carrier lifetime and accordingly the diffusion length in polycrystalline semiconductor materials is known to be detrimentally influenced by disordered interfaces like grain boundaries (GBs). The GB light beam induced current (GB-LBIC) technique is suitable for the extraction of the minority charge carrier diffusion length in unprocessed...

Liquid phase crystallization of silicon is a promising technology to grow crystalline silicon thin films on glass. It has already been demonstrated that open circuit voltages of up to 656 mV and efficiencies of up to 11.8% can be achieved by this technique. Nevertheless further improvements are required to become competitive with wafer based silico...

Liquid-phase crystallization (LPC) has proven to be a suitable method to grow large-grained silicon films on commercially well-available glass substrates. Zone-melting crystallization with high-energy-density line sources such as lasers or electron beams enabled polycrystalline grain growth with wafer equivalent morphology. However, the electronic...

Only recently, the quality of liquid phase crystallized silicon directly on glass substrates made a huge leap towards the quality of multi-crystalline wafers with open circuit voltages well above 600 mV. In this paper, we investigate the material quality in order to identify the factors limiting further performance improvements. We employ photolumi...

We fabricated interdigitated back-contact silicon hetero-junction solar cells based on thin-film absorbers on glass. The Si absorbers were directly deposited on the glass and crystallized using liquid phase crystallization. To compare whether our contact system is applicable to a wide range of initial absorber conditions two different types of prec...

We investigate the influence of the barrier type and the absorber doping on the open-circuit voltage of liquid phase-crystallized silicon solar cells on glass. It was found that the use of n-type instead of p-type substrates is the major reason for the recently reported boost of the open-circuit voltage ( ) up to values of 656 mV, which is by far e...

Liquid phase crystallized Si thin-film solar cells on nanoimprint textured glass substrates exhibiting two characteristic, but distinct different surface structures are presented. The impact of the substrate texture on light absorption, the structural Si material properties, and the resulting solar cell performance is analyzed. A pronounced periodi...

Emerging liquid phase crystallization (LPC) techniques recently rendered a possible substantial progress in the fabrication of high quality crystalline silicon thin-film solar cells on glass. The implementation of an efficient light trapping texture into such LPC silicon devices is still challenging as an excellent bulk material quality and well-pa...

We present grazing incidence X-ray fluorescence (GIXRF) experiments on 3D periodically textured interfaces of liquid phase crystallized silicon thin-film solar cells on glass. The influence of functional layers (SiOx or SiOx/SiCx) – placed between glass substrate and silicon during crystallization – on the final carbon and oxygen contaminations ins...

Liquid phase crystallization of 10 μm thin silicon layers on glass substrates was performed with a line-shaped continuous wave laser beam. The process window was investigated in terms of the scanning velocity of the laser, pre-heating of the specimens and the applied laser intensity. We have identified the entire process window, in which large-scal...

Thin crystalline silicon solar cells prepared directly on glass substrates by means of liquid-phase crystallization of the absorber utilize only a small fraction of the silicon material used by standard wafer-based silicon solar cells. The material consists of large crystal grains of up to square centimeter area and results in solar cells with open...

We present a back-contact silicon heterojunction system for liquid-phase crystallized absorbers on glass. For structuring interdigitating p-type and n-type contact areas, etch selectivity of alkaline solutions for n-doped and p-doped amorphous Si was used. The cells feature Al or ITO/Ag electrodes. Electrical and optical properties were compared. I...

Nanoarchitectures for solar energy conversion are developed, characterized and integrated in device concepts. In particular thin film solar cells based on silicon nanostructures are proposed which have the potential for >15% efficiencies.

Liquid-phase crystallization (LPC) using line-shaped energy sources such as laser or electron beam has proven to be a suitable method to grow large grained high-quality silicon films onto commercially well-available glass substrates. In this study, we compare cw-diode laser-crystallized absorbers with electron beam-crystallized material using back...

This paper presents the progress made at HZB in material and solar cells prepared by liquid phase crystallization of silicon on glass (LPCSG). Silicon layers, deposited by Plasma enhanced Chemical Vapor Deposition (PECVD) and Electron Beam Physical Vapor Deposition (EB-PVD), are compared after being crystallized with a laser and processed into sola...

Liquid-phase crystallized silicon absorber layers have been applied in heterojunction solar cells on glass substrates with 10.8 % conversion efficiency and an open-circuit voltage of 600 mV. Intermediate layers of SiOx, SiNx, and SiOxNy, as well as the a-Si:H precursor layer, were deposited on 30 cm × 30 cm glass substrates using industrial-type pl...

In this paper we present our latest progress in fabricating high quality crystalline silicon thin film solar cells on glass. Large silicon grains are directly formed via electron-beam induced liquid phase crystallization (LPC) from a nanocrystalline precursor film. The LPC process is carried out on an amorphous SiO2 layer, and both a high quality s...

A wide variety of liquid and solid phase crystallized silicon films are investigated in order to determine the performance limiting defect types in crystalline silicon thin-film solar cells. Complementary characterization methods, such as electron spin resonance, photoluminescence, and electron microscopy, yield the densities of dangling bond defec...

Silicon carbide (SiC) is a promising material for the fabrication of optoelectronic devices. In the amorphous state physical-vapor-deposited SiC is already an essential part of the production of electron beam liquid phase crystallized silicon absorbers, because of its good wettability for the silicon melt. The resulting polycrystalline thin film ab...

Tailored crystalline Si thin films are prepared in a slot die- or spin-coating process with Si precursor solutions based on neopantasilane and a subsequent crystallization process. These solution-processed films with a thickness from a few nanometers to 4 μm exhibit excellent key characteristics for the development of high-quality solution-based cr...

We fabricate thin epitaxial crystal silicon solar cells on display glass and fused silica substrates overcoated with a silicon seed layer. To confirm the quality of hot-wire chemical vapor deposition epitaxy, we grow a 2-µm-thick absorber on a (100) monocrystalline Si layer transfer seed on display glass and achieve 6.5% efficiency with an open cir...

Liquid phase crystallization (LPC) using e-beam or CW-laser line sources of amorphous or nanocrystalline silicon films has emerged as new method to form high quality absorbers on cheap substrates. A disadvantage of electron beam crystallization was the necessity to use amorphous SiCxSiCx layers in contact with the silicon to maintain a stable cryst...

The crystallization of thin silicon films directly on glass with a material quality comparable to commercially available multi-crystalline silicon wafers is one of the major goals in thin film technology. In the past the resulting poly-crystalline silicon layers fabricated using the solid phase crystallization (SPC) method suffered from a number of...

The present article gives a summary of recent technological and scientific developments in the field of polycrystalline silicon (poly-Si) thin-film solar cells on foreign substrates. Cost-effective fabrication methods and cheap substrate materials make poly-Si thin-film solar cells promising candidates for photovoltaics. However, it is still the ch...

We investigate the characteristics of intra-grain and grain boundary defects in polycrystalline Si films, by employing quantitative electron paramagnetic resonance measurements on liquid phase crystallized layers with an average grain size of 200 mu m and tailored solid phase crystallized Si layers with similar intra-grain morphology but systematic...

Large grained polycrystalline silicon (poly-Si) absorbers were realized by electron beam induced liquid phase crystallization on 2 μm periodically patterned glass substrates and processed into a-Si:H/poly-Si heterojunction thin-film solar cells. The substrates were structured by nanoimprint lithography using a UV curable hybrid polymer sol-gel resi...

Macroscopic graphene films buried below amorphous and crystalline silicon capping layers are studied by Raman backscattering spectroscopy and Hall-effect measurements. The graphene films are grown by chemical vapor deposition on copper foil and transferred to glass substrates. Uncapped films possess charge-carrier mobilities of 2030 cm2/Vs at hole...

In this paper we present silicon heterojunction solar cells based on polycrystalline silicon (poly-Si) prepared by electron-beam induced liquid phase crystallisation. A single sided contact system has been developed to tap the full potential of the heterojunction concept. Open-circuit voltages as high as 582 mV demonstrate the high potential of pol...

Polycrystalline silicon thin films were prepared by depositing amorphous or microcrystalline silicon layers onto glass substrates and subsequent crystallization via solid or liquid phase crystallization approaches. Differences in layer morphology and quality were characterized using low temperature photoluminescence (PL) spectroscopy and electron b...

Liquid phase crystallization (LPC) is a promising technique to fabricate high-quality polycrystalline silicon absorber layers on cheap glass substrates. Recently, we achieved open-circuit voltages above 580mV using a silicon heterojunction and a newly developed single-sided contact system. However, the still moderate efficiency of 5.7% can be attri...

We report progress made at the National Renewable Energy Laboratory (NREL) on crystal silicon solar cells fabricated by epitaxially thickening thin silicon seed layers on glass using hot-wire chemical vapor deposition. Four micron thick devices grown on single-crystal silicon layer transfer seeds on glass achieved open circuit voltages (Voc) over 6...

Silicon nanowires (SiNW) were formed on large grained, electron-beam crystallized silicon (Si) thin films of only ∼6 μm thickness on glass using nanosphere lithography (NSL) in combination with reactive ion etching (RIE). Electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) studies revealed outstanding structural prope...

In polycrystalline thin film solar cells on glass with an electron beam crystallized absorber (ERA) of 10 μm thickness and an amorphous silicon hetero-emitter an open circuit voltage of 545 mV [1] has been achieved which proves the high electronic quality of the absorber material. However, efficiencies are currently at moderate 4.7%, mainly due to...

Thin film hetero-emitter solar cells with large-grained poly-silicon absorbers of around 10 µm thickness have been prepared on glass. The basis of the cell concept is electron-beam-crystallization of an amorphous or nanocrystalline silicon layer deposited onto a SiC:B layer. The SiC:B layer covers a commercially well available glass substrate, serv...

The properties of electron-beam crystallized, large-grained silicon layers of about 10 mu m thickness on glass have been studied by combining EBIC, EBSD and photoluminescence. It is found that most grains are free of dislocations. From a detailed analysis based on the dependence of EBIC collection efficiency on beam energy we conclude that the reco...

Polycrystalline silicon on glass has been prepared by zone melting crystallization of 7 15 m thick amorphous nano crystalline silicon layers with a line shaped electron beam. Silicon was deposited onto glass substrates, covered by SiC SiC B layers, which act as adhesive layer and barrier against impurity diffusion. Si crystallites are grown ranging...

Sufficient optical thickness and a minimum of recombination losses are the requirements for efficient silicon thin film solar cells with efficiencies above 15 . A capable solution would be a 5 10 m thick polycrystalline Si absorber [1] grown on a low cost substrate and completed to a solar cell by an amorphous a Si H heteroemitter [2]. This article...