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 management (LM) foil on the front-side of a tandem solar cell processed on a wafer with a planar front-side and textured back-side. This way the PCE of monolithic, 2-terminal perovskite/silicon-heterojunction tandem solar cells is significantly improved from 23.4% to 25.5%. Furthermore, we validate an advanced numerical model for our fabricated device and use it to optically optimize a number of device designs with textures at different interfaces with respect to the PCE and energy yield. These simulations predict a slightly lower optimal bandgap of the perovskite top cell in a textured device as compared to a flat one and demonstrate strong interdependency between the bandgap and the texture position in the monolithic stack. We estimate the PCE potential for the best performing both-side textured device to be 32.5% for a perovskite bandgap of 1.66 eV. Furthermore, the results show that under perpendicular illumination conditions, for optimized designs, the LM foil on top of the cell performs only slightly better than a flat anti-reflective coating. However, under diffuse illumination, the benefits of the LM foil are much greater. Finally, we calculate the energy yield for the different device designs, based on true weather data for three different locations throughout the year, taking direct as well as diffuse illumination fully into account. The results further confirm the benefits of front-side texture, even more for BIPV applications. Overall, devices built on a both-side textured silicon wafer perform best. However, we show that devices with textured LM foils on the cell's front-side are a highly efficient alternative.
Tandem solar cells combining silicon and perovskite absorbers have the potential to outperform state-of-the-art high efficiency silicon single junction devices. However, the practical fabrication of ...monolithic silicon/perovskite tandem solar cells is challenging as material properties and processing requirements such as temperature restrict the device design. Here, we fabricate an 18% efficient monolithic tandem cell formed by a silicon heterojunction bottom- and a perovskite top-cell enabling a very high open circuit voltage of 1.78 V. The monolithic integration was realized vialow temperature processing of the semitransparent perovskite sub-cell where an energetically aligned electron selective contact was fabricated by atomic layer deposition of tin oxide. The hole selective, transparent top contact was formed by a stack of the organic hole transport material spiro-OMeTAD, molybdenum oxide and sputtered indium tin oxide. The tandem cell design is currently limited by the photocurrent generated in the silicon bottom cell that is reduced due to reflectance losses. Based on optical modelling and first experiments, we show that these losses can be significantly reduced by combining optical optimization of the device architecture including light trapping approaches.
Terawatt-scale photovoltaics: Transform global energy Haegel, Nancy M; Atwater, Jr, Harry; Barnes, Teresa ...
Science (American Association for the Advancement of Science),
05/2019, Letnik:
364, Številka:
6443
Journal Article
Recenzirano
Odprti dostop
Improving costs and scale reflect looming opportunities
Solar energy has the potential to play a central role in the future global energy system because of the scale of the solar resource, its ...predictability, and its ubiquitous nature. Global installed solar photovoltaic (PV) capacity exceeded 500 GW at the end of 2018, and an estimated additional 500 GW of PV capacity is projected to be installed by 2022–2023, bringing us into the era of TW-scale PV. Given the speed of change in the PV industry, both in terms of continued dramatic cost decreases and manufacturing-scale increases, the growth toward TW-scale PV has caught many observers, including many of us (
1
), by surprise. Two years ago, we focused on the challenges of achieving 3 to 10 TW of PV by 2030. Here, we envision a future with ∼10 TW of PV by 2030 and 30 to 70 TW by 2050, providing a majority of global energy. PV would be not just a key contributor to electricity generation but also a central contributor to all segments of the global energy system. We discuss ramifications and challenges for complementary technologies (e.g., energy storage, power to gas/liquid fuels/chemicals, grid integration, and multiple sector electrification) and summarize what is needed in research in PV performance, reliability, manufacturing, and recycling.
While perovskite solar cells have reached competitive efficiency values during the last decade, stability issues remain a critical challenge to be addressed for pushing this technology towards ...commercialisation. In this study, we analyse a large homogeneous dataset of Maximum Power Point Tracking (MPPT) operational ageing data that we collected with a custom-built High-throughput Ageing System in the past 3 years. In total, 2,245 MPPT ageing curves are analysed which were obtained under controlled conditions (continuous illumination, controlled temperature and atmosphere) from devices comprising various lead-halide perovskite absorbers, charge selective layers, contact layers, and architectures. In a high-level statistical analysis, we find a correlation between the maximum reached power conversion efficiency (PCE) and the relative PCE loss observed after 150-hours of ageing, with more efficient cells statistically also showing higher stability. Additionally, using the unsupervised machine learning method self-organising map, we cluster this dataset based on the degradation curve shapes. We find a correlation between the frequency of particular shapes of degradation curves and the maximum reached PCE.
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%. Further improvements are reached by reducing the current mismatch of the certified device. The top contact and perovskite thickness optimization allowed increasing the
J
SC
above 19.5 mA cm
−2
, enabling a remarkable tandem PCE of 26.0%, however with a slightly limited fill factor (FF). To test the dependency of the FF on the current mismatch between the sub-cells, the tandems'
J
-
V
curves are measured under various illumination spectra. Interestingly, the reduced
J
SC
in unmatched conditions is partially compensated by an enhancement of the FF. This finding is confirmed by electrical simulations based on input parameters from reference single junction devices. The simulations reveal that especially the FF in the experiment is below the expected value and show that with improved design we could reach 29% PCE for our monolithic perovskite/silicon tandem device and 31% PCE if record perovskite and silicon cell single junctions could be combined in tandem solar cells.
We present a highly efficient monolithic perovskite/silicon tandem solar cell and analyze the tandem performance as a function of photocurrent mismatch with important implications for future device and energy yield optimizations.
In this contribution, the effectiveness of an RbF post deposition treatment (PDT) is evaluated in dependence on the Cu content of the absorber layer of Cu(In,Ga)Se 2 solar cells. It is shown that the ...PDT only acts beneficially on the open-circuit voltage and fill factor (FF) on samples with rather high Cu content, while it deteriorates all parameters of the solar cells in samples with low Cu content. In order to clarify the behavior of the open-circuit voltage, the well-known exchange mechanism of Rb and Na during the PDT is analyzed as a function of the Cu content of the absorber layers and discussed in regard to theoretical publications. Furthermore, a model explaining the observed effect on the FF based on the formation of an RbInSe 2 (RIS) layer during the RbF-PDT is proposed. The model supposes that the RIS layer acts as a barrier for the photocurrent and therefore lowers the FF. It is evaluated theoretically in dependence of the properties of the RIS layer using one-dimensional solar cell capacitance simulator (SCAPS) simulations. Finally, the proposed model is also tested and confirmed experimentally by directly depositing RIS onto untreated Cu(In,Ga)Se 2 layers.
Hybrid multijunction solar cells comprising hydrogenated amorphous silicon and an organic bulk heterojunction are presented, reaching 11.7% power conversion efficiency. The benefits of merging ...inorganic and organic subcells are pointed out, the optimization of the cells, including optical modeling predictions and tuning of the recombination contact are described, and an outlook of this technique is given.
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 indexes (n) in the range 2.1-2.7 and conductivity of 10 -4 -10 -1 S/cm were applied. Both optical simulations and experimental results suggest different optimizing approaches for short-circuit current (JSC) enhancement depending on the surface morphology of the silicon wafer. While planar wafers benefit from an improved antireflection effect using less transparent (n ~ 2.7) and thicker films, textured wafers require thinner highly transparent layers (n <; 2.7) with less parasitic absorption, since the reflectance losses are already low due to the texture. Finally, a thickness optimization of the (n)nc-SiO x :H leads to a conversion efficiency of 21.6%, a fill factor of 80.0%, an open-circuit voltage of 729 mV, and J SC-EQE = 40.0 mA/cm 2 .
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/cm
have been demonstrated on this material, however, a low fill factor was limiting the performance. In this work we present our latest cell progress on 13 μm thin poly-crystalline silicon fabricated by the liquid phase crystallization directly on glass. The contact system uses passivated back-side silicon hetero-junctions, back-side KOH texture for light-trapping and interdigitated ITO/Ag contacts. The fill factors are up to 74% and efficiencies are 13.2% under AM1.5 g for two different doping densities of 1 · 10
/cm
and 2 · 10
/cm
. The former is limited by bulk and interface recombination, leading to a reduced saturation current density, the latter by series resistance causing a lower fill factor. Both are additionally limited by electrical shading and losses at grain boundaries and dislocations. A small 1 × 0.1 cm
test structure circumvents limitations of the contact design reaching an efficiency of 15.9% clearly showing the potential of the technology.
We present a detailed analysis of the photo-current potentials and losses in thin film crystalline silicon solar cells on glass. The effects of texturing the silicon backside, applying a diffuse back ...reflector and a textured anti-reflection foil were analysed. Light beam induced current measurements were used to determine the losses due to local effects like the absorber contact, cracks in the absorber and grain boundaries. Detailed loss analysis in combination with ray-tracing simulations showed that the maximum light trapping potential imposed by geometrical optics has nearly been achieved. The photocurrent losses due to incomplete carrier collection and parasitic absorption were accounted for using a theoretical model. For the investigated, textured, n-doped cell with reflector and anti-reflection foil, the short circuit current density (JSC) was 28.9mA/cm2 and the main loss factors were direct reflection (3.4mA/cm2), electrical shading effects due to the absorber contact (3.1mA/cm2) and incomplete carrier collection due to surface/bulk recombination (1.6mA/cm2). Using the presented light trapping scheme we obtained the following efficiencies: 11.8% for a p-doped and 12.1% for an n-doped crystalline silicon absorber. Finally, the potentials for efficiencies beyond 14% are discussed.
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•12 % efficiency was obtained for 11 µm thick, liquid-phase crystalized Si on glass.•Using KOH texturing and anti-reflection foil, a JSC of 28.9 mA/cm2 was achieved.•Current density losses were characterized using LBIC, optics, EQE and simulations.•Main loss factors were direct reflection, the absorber contact and recombination.•Max. light trapping potential was almost reached, using a backside pyramid texture.
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