Bernd Stannowski

Helmholtz-Zentrum Berlin für Materialien und Energie | HZB · PVcomB

In perovskite/silicon tandem solar cells, the utilization of silicon heterojunction (SHJ) solar cells as bottom cells is one of the most promising concepts. Here, we present optimization strategies for the top cell processing and their integration into SHJ bottom cells based on industrial Czochralski (Cz)-Si wafers of 140 μm thickness. We show that...

Due to the unique microstructure of hydrogenated nanocrystalline silicon oxide (nc‐SiOx:H), the optoelectronic properties of this material can be tuned over a wide range, which makes it adaptable to different solar cell applications. In this work, the authors review the material properties of nc‐SiOx:H and the versatility of its applications in dif...

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...

Improved stability and efficiency of two-terminal monolithic perovskite-silicon tandem solar cells will require reductions in recombination losses. By combining a triple-halide perovskite (1.68 electron volt bandgap) with a piperazinium iodide interfacial modification, we improved the band alignment, reduced nonradiative recombination losses, and e...

Nano‐textured surfaces are an intriguing approach for optimizing the optical characteristics for monolithic perovskite/silicon tandem solar cells. Here, the development of different textures of silicon surfaces using various commercial additives is presented and their performance in silicon heterojunction (SHJ) and SHJ–perovskite tandem solar cells...

We study the outdoor operation of an up-scaled thermally integrated photovoltaic-electrolyser (PV-EC), constructed using a heat exchanger made of low-cost materials, compared to its non-integrated counterpart to quantify heat transfer and its effects. Thermal coupling of the PV and EC can reduce the difference between their temperatures, benefittin...

Perovskite–silicon tandem solar cells offer the possibility of overcoming the power conversion efficiency limit of conventional silicon solar cells. Various textured tandem devices have been presented aiming at improved optical performance, but optimizing film growth on surface-textured wafers remains challenging. Here we present perovskite–silicon...

Wide bandgap halide perovskite materials show promising potential to pair with silicon bottom cells. To date, most efficient wide bandgap perovskites layers are fabricated by spin-coating, which is difficult to scale up. Here, we report on slot-die coating for an efficient, 1.68 eV wide bandgap triple-halide (3halide) perovskite absorber, (Cs0.22FA...

The industrial mass production of heterojunction silicon solar cells has gained significant interest over the last few years as the technology offers high efficiencies of 26.7% for an interdigitated back contacted (IBC) lab cell [1] and above 25% for two-side contacted solar cells on industrial relevant processes[2]–[5]. Today a major focus in indu...

For vehicle integrated photovoltaics (VIPV) there are possibly specific requirements on the speed of maximum power point tracking. However, a certain delay in the response of solar cells to fast irradiance changes might impact those requirements on the MPPT. The subject of this work is therefore the investigation of the transient electrical behavio...

The perovskite material has been introduced as a novel type of wide-bandgap (WBG) light absorber in photovoltaics. Recently, perovskite/crystalline silicon (c-Si) tandem solar cells have achieved efficiencies beyond those of the silicon single-junction limit, which makes them very promising as a next-generation solar cell technology to further incr...

How can we reduce the Indium content in SHJ solar cells, keep high efficiency and ensure module reliability? Strategies for Indium reduction in SHJ solar cells are presented: 1. Thinner Indium TCO + SiOx cap work fine, approx. 75% less Indium with highest performance + stable cells - but still Indium needed; 2. AZO as a replacement can achieve hi...

Perovskite/silicon tandem solar cells allow to overcome the power conversion efficiency limit of market-dominating silicon solar cells. So far, various textured tandem devices were presented aiming at improved optical performance, but highest efficiencies were still realized on polished silicon wafer cells enabling superior perovskite layer propert...

Perovskite solar cells (PSCs) have shown great potential for next-generation photovoltaics. One of the main barriers to their commercial use is their poor long-term stability under ambient conditions and, in particular, their sensitivity to moisture and oxygen. Therefore, several encapsulation strategies are being developed in an attempt to improve...

LCA studies of perovskite-on-silicon tandem (PST) cells have so far been heavily reliant on laboratory data and process data from test facilities to project environmental impacts, producing results that differ...

Correction for ‘New insights into the environmental performance of perovskite-on-silicon tandem solar cells – a life cycle assessment of industrially manufactured modules’ by Martin Roffeis et al. , Sustainable Energy Fuels , 2022, 6 , 2924–2940, https://doi.org/10.1039/D2SE00096B.

We present results on perovskite/silicon tandem solar cells with almost 30% power conversion efficiency. They comprise sinusoidal nanotextures between top and bottom cells and optically advanced rear reflectors with a dielectric buffer layer.

To increase the efficiency in p–type wafer–based SHJ technology, one of the most crucial challenges is the achievement of excellent surface passivation. In this work, chemical passivation techniques known for n–type technology are successfully applied on p–type Float–Zone (FZ) wafers, and wafer surface passivation quality is correlated with paramet...

Silicon Heterojunction has become a promising technology to substitute passivated emitter and rear contact (PERC) solar cells in pursuance of lower levelized cost of electricity through high efficiency devices. While high open circuit voltages and fill factors are reached, current loss related to the front and rear contacts, such as the transparent...

We report on the setting up of a practical demonstration vehicle with integrated photovoltaics based on the Streetscooter WORK L electrically‐driven light commercial vehicle. Our demonstrator vehicle is equipped with 15 modules based on the crystalline Si/amorphous Si heterojunction technology. The nominal total peak power under standard testing co...

Formamidinium iodide (FAI) based perovskite absorbers have been shown to be ideal candidates for highly efficient and operationally stable perovskite solar cells (PSC). A major challenge for formamidinium lead iodide (FAPbI3) is to suppress the phase transition from the photoactive black phase into yellow nonperovskite δ‐phase. Several approaches t...

Monolithic perovskite/silicon tandem solar cells recently surpassed the efficiency of silicon single‐junction solar cells. Most tandem cells utilize >250 µm thick, planarized float‐zone (FZ) silicon, which is not compatible with commercial production using <200 µm thick Czochralski (CZ) silicon. We demonstrate perovskite/silicon tandem cells based...

We present enhanced optical performance in perovskite/silicon tandem solar cells with smooth periodic nanotextures. Reflection losses in experimental devices are reduced by 1 mA/cm², enabling a power conversion efficiency >26%.

Efficiency from hole-selective contacts Perovskite/silicon tandem solar cells must stabilize a perovskite material with a wide bandgap and also maintain efficient charge carrier transport. Al-Ashouri et al. stabilized a perovskite with a 1.68–electron volt bandgap with a self-assembled monolayer that acted as an efficient hole-selective contact tha...

Efficient light management is key for optimal performance of silicon solar cells. For monocrystalline single‐junction devices, there is an established industrially viable technology using pyramidal micro‐structured silicon wafers. As the efficiencies of market‐dominating silicon single‐junction solar cells are approaching their physical limit, inno...

Silicon heterojunction (SHJ) solar cells represent a promising technological approach towards higher photovoltaics efficiencies and lower fabrication cost. While the device physics of SHJ solar cells have been studied extensively in the past, the ways in which nanoscopic electronic processes such as charge-carrier generation, recombination, trappin...

Doped hydrogenated nanocrystalline (nc-Si:H) and silicon oxide (nc-SiOx:H) materials grown by plasma-enhanced chemical vapor deposition have favourable optoelectronic properties originated from their two-phase structure. This unique combination of qualities, initially, led to the development of thin-film Si solar cells allowing the fabrication of m...

An integrated photovoltaic-electrolyser with a solar collection area of 294 cm² was constructed and its performance, represented by the solar to hydrogen (STH) conversion efficiency and hydrogen production rate mH2 in various outdoor and indoor conditions, was investigated by measurements of the product gas streams. The device was composed of silic...

Stable perovskites with ionic salts Ionic liquids have been shown to stabilize organic-inorganic perovskite solar cells with metal oxide carrier-transport layers, but they are incompatible with more readily processible organic analogs. Lin et al. found that an ionic solid, a piperidinium salt, enhanced the efficiency of positive-intrinsic-negative...

Monolithic [Cs0.05(MA0.17FA0.83)0.95]Pb(I0.83Br0.17)3/Cu(In,Ga)Se2 (perovskite/CIGS) tandem solar cells promise high performance and can be processed on flexible substrates, enabling cost-efficient and ultra-lightweight space photovoltaics with power-to-weight and power-to-cost ratios surpassing those of state-of-the-art III-V semiconductor-based m...

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...

We demonstrate shallow nanotextures for light management in solution-processed perovskite and in silicon heterojunction solar cells. Reduced reflectance losses enable increased efficiencies of nanotextured perovskite-silicon tandem solar cells.

In this article, we report on the properties of indium tin oxide (ITO) deposited on thin-film silicon layers designed for the application as carrier selective contacts for silicon heterojunction (SHJ) solar cells. We find that ITO deposited on hydrogenated nanocrystalline silicon (nc-Si:H) layers presents a significant drop on electron mobility µ...

Silicon heterojunction (SHJ) solar cells rely on excellent surface passivation of the crystalline wafer. This article reports on the development of wet chemical processes varying the texturing and optimizations of the final clean processes for Czochralski–silicon wafers used in SHJ solar cells. Three different additives are used to modify both the...

Silicon heterojunction (SHJ) solar cell technology has the potential to be the next mainstream industrial solar cell design due to its high efficiency and lean production process with only four main process steps. While two-side contacted SHJ cells have very high open circuit voltages (Voc) >740 mV, they tend to be lower in short circuit current de...

In this paper, we demonstrate a new benchmark for a large area photoelectrochemical-photovoltaic (PEC-PV) solar water splitting device with a metal oxide-based top absorber. The stand-alone 50 cm² device consists of cobalt phosphate-coated tungsten-doped BiVO4 (CoPi/W:BiVO4) photoanodes combined with series-connected silicon heterojunction (SHJ) so...

Metal halide perovskites show great promise to enable highly efficient and low cost tandem solar cells when being combined with silicon. Here, we combine rear junction silicon heterojunction bottom cells with p-i-n perovskite top cells into highly efficient monolithic tandem solar cells with a certified power conversion efficiency (PCE) of 25.0 %....

In this study we make a detailed comparison between indium tin oxide (ITO), aluminum-doped zinc oxide (ZnO:Al) and hydrogenated indium oxide (IO:H) when applied on the illuminated side of rear-junction silicon heterojunction (SHJ) solar cells. ITO being the state of the art material for this application, ZnO:Al being an attractive substitute due to...

To make the concept of building-integrated solar cells viable, the latter should possess an increased tolerance towards light incident angle and intensity that naturally change along the day, among other required properties. In this work, three solar cell technologies as candidates for building-integrated applications are compared regarding their n...

Transparent conductive oxide (TCO) layers of aluminum-doped zinc oxide (ZnO:Al) were investigated as a potential replacement of indium tin oxide (ITO) for the front contact in silicon heterojunction (SHJ) solar cells in the rear emitter configuration. It was found that ZnO:Al can be tuned to yield cell performance almost at the same level as ITO wi...

Perovskite/silicon tandem solar cells are attractive for their potential for boosting cell efficiency beyond the crystalline silicon (Si) single‐junction limit. However, the relatively large optical refractive index of Si, in comparison to that of transparent conducting oxides and perovskite absorber layers, results in significant reflection losses...

Efficient light management in monolithic perovskite/silicon tandem solar cells is one of the prerequisites for achieving high power conversion efficiencies (PCEs). Textured silicon wafers can be utilized for light management, however, this is typically not compatible with perovskite solution processing. Here, we instead employ a textured light mana...

When designing silicon heterojunction (SHJ) solar cells with a rear-emitter (RE) configuration the requirements of the conductivity of the transparent conducting oxide (TCO) at the front side are relaxed due to the contribution of lateral current flow within the silicon wafer. In this study, we analyze two approaches that can be implemented to bene...

Encapsulation materials are of critical importance for long-term reliability and safety of PV modules. Only months in the field may lead to drastic power output degradation for example due to PID and also in the longer run adhesion and discoloration issues (Hot Spot) can reduce power output or even may lead to critical electrical safety issues. The...

Silicon heterojunction (SHJ) solar cells have been increasingly attracting attention to the photovoltaic community in the last years due to their high efficiency potential and the lean production process. We report on the development of a stable baseline process for SHJ cells with focus on the optical improvement of the solar cells’ front side. An...

Sputtered indium tin oxide (ITO) is a widespread used material for application as transparent conducting oxide as the front contact of rear-junction silicon heterojunction solar cells. Standard ITO films suffer from too high parasitic absorption in both the short-and the long-wavelength range. The aim of this contribution is to investigate lower ab...

We report on the investigation and comparison of two different processing approaches for interdigitated back contacted silicon heterojunction solar cells: our photolithography-based reference procedure and our newly developed shadow mask process. To this end, we analyse fill factor losses in different stages of the fabrication process. We find that...

Polycrystalline-silicon-on-oxide (POLO) junctions and related contacting schemes have shown their capability to facilitate high efficiencies for solar cells with passivating selective contacts [1-3]. In this work the front contacting of two-side contacted POLO cells with sputtered aluminum-doped zinc oxide (ZnO:Al) has been investigated. Different...

We performed optical simulations using hydrogenated nanocrystalline silicon oxide (nc-SiOx:H) as n-doped interlayer in monolithic perovskite/c-Si heterojunction tandem solar cells. Depending on the adjustable value of its refractive index (2.0 – 2.7) and thickness, nc-SiOx:H allows to optically manage the infrared light absorption in the c-Si botto...

Hydrogenated nanocrystalline silicon oxide (nc-SiOx:H) films have demonstrated a unique combination of low parasitic absorption and high conductivity. Here, we report on the use of n-type nc-SiOx:H as front surface field (FSF) in rear-emitter silicon heterojunction (SHJ) solar cells exhibiting excellent electrical cell parameters at a thickness dow...

In photovoltaics, light concentration increases device efficiency and enables the possibility of large material savings, which reduces production costs significantly and circumvents the potential scarcity of raw materials. Convex-planar cylindrical lenses can be used for one-dimensional concentration of light, reducing the illuminated area to a nar...

The conversion efficiency of silicon heterojunction solar cells is limited by current losses mainly in the front layer stack. In order to minimize these losses, we implemented n-doped nanocrystalline silicon oxide (nc-SiOx:H) as front surface field to enhance both transparency and conductivity, thus improving the fill factor. Layers with refractive...

We report on two different approaches to fabricate interdigitated back contact silicon heterojunction solar cells without using indium tin oxide (ITO). The standard ITO/Ag backend is either modified by replacing ITO with aluminum-doped zinc oxide (AZO) or completely replaced by a sole aluminum (Al) layer. The very transparent AZO enhances the optic...

Plasmon imaging using energy filtered transmission electron microscopy (EFTEM) has been a well‐established technique for investigating mixed phase silicon systems for more than a decade [1]. To image the silicon distribution typically an energy window of 4 eV centered at 17 eV is used. With this approach the signal contains significant contribution...

We investigated hydrogenated nanocrystalline silicon (nc-Si:H) films as doped emitter layers for silicon heterojunction solar cells. Firstly, we focused on the effect of the nc-Si:H deposition conditions and film growth on the intrinsic hydrogenated amorphous silicon passivation layer ((i)a-Si:H) underneath. Three different p-doped emitters were co...

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...

Amorphous/microcrystalline/crystalline silicon (a-Si:H/μc-Si:H/c-Si) triple junction solar cells have been developed to directly split water, for which operating voltages (Voc) >1.5 V (depending on the catalysts) are needed. These cells are an inexpensive alternative to high efficiency, high voltage multi junction solar cells based on scarce elemen...

Nanocrystalline silicon suboxides (nc-SiOx) have attracted attention during the past years for the use in thin-film silicon solar cells. We investigated the relationships between the nanostructure as well as the chemical, electrical, and optical properties of phosphorous, doped, nc-SiO0.8:H fabricated by plasma-enhanced chemical vapor deposition....

Architectures with various degrees of integration are investigated for water splitting devices using the energy of light for fuel production. The many approaches presented in literature for such ‘photo driven catalytic (PDC) devices’ are reviewed and discussed in perspective of their scalability to large area. Then, back-of-the-envelope type techno...

A novel emitter patterning method for back-contacted Si heterojunction solar cells is presented, which combines laser processing and wet etching of a mask layer stack with self-aligned repassivation, thus reducing the process complexity, as compared with the commonly used emitter patterning methods. Lifetime samples demonstrate that with a suitable...

The passivation quality at the interface between dielectric interlayer (IL) stacks and liquid-phase crystallized silicon (LPC-Si) was investigated by means of high-frequency capacitance–voltage (C–V) measurements. The developed device structure was based on a molybdenum layer sandwiched between the glass substrate and the IL/LPC-Si stack. C–V curve...

An integrated water-splitting device based on a triple-junction silicon-based solar cell (a-Si:H/a-Si:H/μc-Si:H; a-Si=amorphous silicon, μc-Si=microcrystalline) in superstrate configuration modified with catalysts at the back and front contacts is described. In this configuration, the solar cell is illuminated by the glass substrate, while the back...