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23.6%-efficient monolithic perovskite/silicon tandem solar cells with improved stability
Abstract and Figures
As the record single-junction efficiencies of perovskite solar cells now rival those of copper indium gallium selenide, cadmium telluride and multicrystalline silicon, they are becoming increasingly attractive for use in tandem solar cells due to their wide, tunable bandgap and solution processability. Previously, perovskite/silicon tandems were limited by significant parasitic absorption and poor environmental stability. Here, we improve the efficiency of monolithic, two-terminal, 1-cm2 perovskite/silicon tandems to 23.6% by combining an infrared-tuned silicon heterojunction bottom cell with the recently developed caesium formamidinium lead halide perovskite. This more-stable perovskite tolerates deposition of a tin oxide buffer layer via atomic layer deposition that prevents shunts, has negligible parasitic absorption, and allows for the sputter deposition of a transparent top electrode. Furthermore, the window layer doubles as a diffusion barrier, increasing the thermal and environmental stability to enable perovskite devices that withstand a 1,000-hour damp heat test at 85 ∘C and 85% relative humidity.
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... However, these silicon cells can be adapted to the particular context of tandem and also undergo special treatment to achieve better performance in this configuration. For example, with an additional layer of MgF 2 or LiF as an anti-reflection coating on the front surface, reflection losses can be reduced to less than 2%, see Fig. 1.10a [66][67][68]. Another optical loss results from the escape of long wavelength photons from the backside (due to back reflection). ...
... This results in periodic nanostructures that are carefully tailored to efficiently trap weakly absorbing infrared photons as shown in Fig. 1.10b [70]. Bush et al. also demonstrated that the SiNP layer on the backside could improve the collection of infrared light [68]. Finally, the bottom silicon cell experiences higher long-wave optical loss (as a percentage of total incident light) than in conventional single-junction cells. ...
... The MAPbI 3 is now replaced by double, triple or even quadruple cation compositions, with at least 2 different halogens. These structures are indeed more stable and have higher UV and heat resistance [68,83,85,86]. Thus all the latest record single-junction perovskite cells since 2016 use a composition with at least two cations, most often MA/FA, see Table A.1 in Appendix A. Nevertheless, there are many other compositions, with now more than 400 different families of perovskites in the photovoltaic field. ...
The current photovoltaic market is dominated by silicon-based solar cells, whose laboratory performance is getting closer and closer to the theoretical limit. To overcome this limit, the most promising approach is the use of a tandem architecture combining a wide bandgap solar cell with a silicon cell. The objective of the thesis is to fabricate a high efficiency, stable and large-size semi-transparent perovskite cell for the realization of a 4-terminal silicon-based tandem cell. The optical losses due to material absorption and reflection at the various interfaces were analyzed in detail by coupling optical modelling and characterization, in order to guide the development of efficient semi-transparent solar cells. In particular, the work focused on replacing the metallic back contact of conventional perovskite cells with a transparent electrode made of ITO, IZO or IO :H, and introducing selective PTAA and SnO₂ contacts. The stacks and processes were optimized to minimize optical and electrical losses, and improve the stability of the devices. Experimental studies on small area perovskite cells and filtered silicon cells have shown a potential efficiency of up to 25%. They also allowed a better understanding of the temporal evolution of the electrical properties, marked by a temporary electrical barrier observed in the first days after the synthesis, and then fading. In addition, the development of an encapsulation process has made it possible to maintain a semi-transparent perovskite cell at more than 90% of its initial efficiency for more than 2 months. Finally, an increase in the size of the devices up to 16 cm² was achieved by the series connection of several cells to form a mini-module with an active surface efficiency of 14.2%, and a perovskite-silicon tandem with the same surface area of 20.8%.
... In recent years, the perovskite material system has gained considerable research attention because of its excellent electronic and optical properties, particularly, its ability to tailor the bandgap and low deposition cost. (Bush et al., 2017a;Chung et al., 2017; Y. C. Kim et al., 2017;M. Liu, Johnston, & Snaith, 2013a Green, Jiang, Soufiani, & Ho-Baillie, 2015;Jang et al., 2016;Jiang, Green, Sheng, & Ho-Baillie, 2015;Li et al., 2015;Shi et al., 2015;L. ...
... of the metal oxide films.4.1.1 Perovskite Solar Cell StructureMost research on PSCs is still focused on single-junction solar cells. However, perovskite and silicon as part of a perovskite/silicon tandem solar cell (TSC) exhibits the largest economic potential, because this combination allows reaching high ECEs, while the manufacturing cost is low.(Bush et al., 2017a;Mohammad I. Hossain et al., 2018a;Jošt et al., 2018;Sahli et al., 2018b;Werner et al., 2018) In this case, the PSC must be integrated on crystalline silicon (c-Si) wafer-based bottom solar cell. Hence, we will focus on device structures in substrate configuration, opposite to solar cells on glass substrates, commonly referred to as solar ...
Metal-halide perovskites are considered as one of the most exciting material systems
due to their excellent optoelectronic properties. Notably, the multi-bandgap properties
of perovskites have opened an emerging prospect for highly efficient tandem solar cell
and color vision applications. So far, only perovskite-based tandem solar cells allow
reaching energy conversion efficiencies exceeding 30% at low manufacturing cost. In
this thesis, efficient solar cells and color sensors are studied based on metal-halide
perovskite materials.
Charge transport/contact layers have a significant impact on the electrical and optical
properties of perovskite solar cells. Particularly, the front contact, which is a part of the
junction of the solar cell, has to be efficient for realizing high energy conversion
efficiency. The front contact must provide a lateral charge transport to the terminals
and should allow efficient light incoupling while maintaining low optical losses. Hence,
In the first part of the thesis, metal-oxides, such as titanium oxide (TiO2), nickel-oxide
(NiO), zinc oxide (ZnO), etc., are investigated as potential front contacts for realizing
efficient perovskite solar cells. High-quality metal oxide films are prepared by spray
pyrolysis deposition (SPD), electron-beam physical vapor deposition (EBPVD), metalorganic
chemical vapor deposition (MOCVD), and atomic layer deposition (ALD)
techniques. As a first step, the study is carried out to investigate the planar perovskite
solar cell performance with different front contacts, which is also used as a reference
device structure for future investigations. Subsequently, the study is progressed to the
textured perovskite solar cells, which combines the benefit of reaching high shortcircuit
current densities and energy conversion efficiencies due to efficient photon
management. Efficient photon management allows enhancing photon absorptions in
perovskite solar cells through light incoupling and/or light trapping. Herein, light
incoupling and light trapping are investigated with the integration of surface textures
(e.g. moth-eye, pyramid, optical metasurfaces, etc.) on top of planar perovskite solar
cells. A non-resonant optical metasurface is additionally studied as an alternative light-trapping
structure for realizing efficient perovskite solar cells, where an array of ZnO
nanowires is realized by the templated electrodeposition through a mask of resist. The
complex requirements of perovskite solar front contacts and the effect of the front
contact on the optics of perovskite solar cells are described in this part of the study.
The optics of solar cells is investigated by 3D finite-difference time-domain (FDTD)
optical simulations and the electrical effects of solar cells are inspected by the 3D finite
element method (FEM). Detailed discussions for the realization of metal oxide films
and the influence of photon management on the photovoltaic performance are
provided.
The second part of this thesis deals with detailed balance calculations and photon
management of perovskite-based tandem solar cells. An extended Shockley–
Queisser model is used to identify fundamental loss mechanisms and link the losses
to the optics of solar cells. The influence of free-carrier absorption of metal oxide films
on the optics of low bandgap and/or tandem solar cells is investigated. Herein, an
optimized design is proposed for the perovskite/silicon tandem solar cell, which has the
potential to reach energy conversion efficiency beyond 30% with a short-circuit current
density exceeding 20 mA cm−2 while using realistic device geometry. A hybrid approach is
used to investigate the optics of perovskite/silicon tandem solar cells by combining 3D
finite-difference time-domain simulations with experimental measurements. Furthermore,
multi-bandgap perovskites are employed as absorbers for investigating high-efficiency
perovskite/perovskite tandem solar cells at low cost. Details on the nanophotonic design
of perovskite-based tandem solar cells are provided.
In the final part of this thesis, multi-bandgap perovskite materials are considered for the
realization of efficient vertically stacked color sensors. The vertically stacked color sensor
consists of three different energy bandgap perovskite diodes (channels), which allows
exhibiting excellent color separation without having any color aliasing or color moiré
error. The complex material properties of multi-bandgap perovskites are determined
by the energy shift modeling. The quantum efficiency of the proposed vertically
stacked color sensor is 3 times higher than the conventional filter-based color sensors.
The current study focuses on the perovskite color sensor for achieving the quantum
efficiency approaching 100%. The quantum efficiency of the investigated sensor is
calculated by 3D finite-difference time-domain simulations. The study is further
advanced to the realization of the multi-channel color sensor for detecting multispectral
imaging, where six individual perovskite diodes are used for the sensor construction.
The six-channel sensor outperforms all other characterized sensors. It enables the
reconstruction of incident spectra that can be applied to a wide range of areas, such
as health, communications, safety, and securities. The colorimetric characterization is
performed based on the calculated spectral responsivities of the investigated color
sensors. Details on the used materials, the device design, and the colorimetric
analysis are provided.
... In the two terminal tandem solar cells, the currents of the two cells must match because they are connected in series [17]. Therefore, the appropriate band gap value of the cell is more limited, with the best value for the bottom cell being 0.94 eV and the best value for the top cell being 1.60 eV [18]. ...
In this paper, three-stage co-evaporation method was used to prepare narrow bandgap CuInSe 2 (CIS) thin-film absorber. The effect of the substrate temperature on the performance of CIS solar cells was investigated. The substrate temperatures of the CIS films varied from 420 • C to 580 • C. The microstructure structure, crystallinity, morphology, and optoelectrical performances of the CIS solar cell were investigated by various characterization methods. We found that the substrate temperature played a great role in the properties of the CIS thin films and solar cell devices: that was the CIS solar cell deposited at low temperature showed poor crystallinity, fine grain size and low efficiency, while CIS solar cell deposited very high temperature also showed high efficiency. However, high substrate temperature can lead to the Indium loss at the surface of the CIS films, although the bulk composition of CIS films did vary much at different substrate, resulting in FF (fill factor) reduce.
... Examples of thermo-curable adhesives include ethylene-vinyl acetate (EVA) (Bush et al. 2017), surlyn ionomer , and polyisobutylene (PIB) (Shi et al. 2017 ...
... Examples of thermo-curable adhesives include ethylene-vinyl acetate (EVA) (Bush et al. 2017), surlyn ionomer , and polyisobutylene (PIB) (Shi et al. 2017 ...
The forest industry is an energy-intensive sector that emits approximately 2% of industrial fossil CO2 emissions worldwide. In Finland, the forest industry is a major contributor to wellbeing and has constantly worked on sustainability issues for several decades. The intensity of fossil fuel use has been continuously decreasing within the sector; however, there is still a lot of potential to contribute to the mitigation of environmental change. Considering the ambitious Finnish climate target to reach carbon-neutrality by 2035, the forest industry is aiming for net-zero emissions by switching fossil fuels to bio-based alternatives and reducing energy demand by improving energy efficiency. Modern pulp mills are expanding the traditional concept of pulp mills by introducing the effective combination of multifunctional biorefineries and energy plants. Sustainably sourced wood resources are used to produce not only pulp and paper products but also electricity and heat as well as different types of novel high-value products, such as biofuels, textile fibres, biocomposites, fertilizers, and various cellulose and lignin derivatives. Thus, the forest industry provides a platform to tackle global challenges and substitute greenhouse-gas-intensive materials and fossil fuels with renewable alternatives.
The performance of perovskite solar cells with inverted polarity ( p-i-n ) is still limited by recombination at their electron extraction interface, which also lowers the power conversion efficiency (PCE) of p-i-n perovskite-silicon tandem solar cells. A ~1 nm thick MgF x interlayer at the perovskite/C 60 interface through thermal evaporation favorably adjusts the surface energy of the perovskite layer, facilitating efficient electron extraction, and displaces C 60 from the perovskite surface to mitigate nonradiative recombination. These effects enable a champion V oc of 1.92 volts, an improved fill factor of 80.7%, and an independently certified stabilized PCE of 29.3% for a ~1 cm ² monolithic perovskite-silicon tandem solar cell. The tandem retained ~95% of its initial performance following damp-heat testing (85 Celsius at 85% relative humidity) for > 1000 hours.
Perovskite/silicon tandem solar cells are a rapidly emerging class of high-efficiency photovoltaic (PV) devices that have demonstrated excellent power conversion efficiencies (PCEs) while promising low-cost manufacturing. In recent years, this technology has been pushed increasingly closer to market entrance. Yet, for true commercial success, PCEs also need to be stable, in line with the warranty certificates of commercial crystalline-silicon (c-Si) PV modules. Bifacial tandem solar cells that collect light at both their sunward and rear side by exploiting the albedo—the scattered and reflected photons from the ground—offer a promising pathway toward a greater stability and energy yield. Thanks to the additional photons arising from the albedo, bifacial solar cells may generate a current larger than their conventional monofacial counterparts, enabling a higher performance. For bifacial monolithic tandems, exploiting such current enhancement requires current matching between top and bottom cells, which mandates the use of a bromide-lean, narrow-band-gap perovskite that is known to suppress halide segregation, thereby significantly improving device stability. In this perspective, we discuss bifacial perovskite/silicon tandem technology in depth, highlighting its great appeal, thanks to its combination of enhanced performance and improved stability with promising low costs, thereby representing a key future technology at the utility scale that can contribute to the formation of a carbon-neutral sustainable economy.
Tandem solar cells (TSCs) represent a promising route to break the Shockley–Queisser limit of single‐junction solar cells. Organic–inorganic hybrid perovskite is an ideal candidate for fabricating TSCs with the superiority of excellent photoelectric properties, bandgap tunability, and low‐temperature solution processability. In this chapter, we summarize the recent progress of perovskite‐based TSCs, including perovskite/crystalline silicon (PVSK/c‐Si), perovskite/organic (PVSK/OPV), and perovskite/perovskite (PVSK/PVSK) solar cells. Then, we introduce the emergence of multi‐junction perovskite‐based tandems. Subsequently, the challenges and potential strategies toward high‐efficiency perovskite‐based TSCs are discussed. Lastly, the conclusions and perspectives on the promising perovskite‐based TSCs are provided.
In recent years, lead mixed halide perovskite materials have been highly efficient in solar cells and other semiconductor technology. Presently, Perovskites solar cells combined with Cesium formamidinium lead mixed halide (FA0.83Cs0.17PbI3-xBrx) are the most widely discussed subject for third-generation solar cells studied among third-generation solar cells in light of their tunable broad bandgap, strong charge carrier mobility, and high efficiency. The perovskite active layers with the hybrid perovskite composition of FA0.83Cs0.17PbI3-xBrx can change bandgap by adjusting the I/Br ratio ranging (x = 0.5, 1.0, 1.5, 2.0, 2.5). We have utilized SCAPS-1D to simulate an n-i-p planer heterojunction PSC by changing the I/Br ratio of FA0.83Cs0.17PbI3-xBrx as an active layer in this paper. It has been demonstrated that when halogen ratios increase, power conversion efficiency (PCE), short-circuit current density (JSC), and fill factor (FF) decrease while open-circuit voltage (VOC) increases. We have discovered that, among all the combinations, FA0.83Cs0.17PbI2.5Br0.5 has the highest efficiency of 23.57% after considering perovskite thickness, defect density, series resistance, and shunt resistance. Finally, we can say that FA0.83Cs0.17PbI2.5Br0.5 as an absorbing perovskite material may generate a high-efficiency solar cell while also performing the role of the top cell in a perovskite-perovskite tandem arrangement.
We demonstrate four and two-terminal perovskite-perovskite tandem solar cells with ideally matched bandgaps. We develop an infrared absorbing 1.2eV bandgap perovskite, FA0.75Cs0.25Sn0.5Pb0.5I3, that can deliver 14.8% efficiency. By combining this material with a wider bandgap FA0.83Cs0.17Pb(I0.5Br0.5)3 material, we reach monolithic two terminal tandem efficiencies of 17.0% with over 1.65 volts open-circuit voltage. We also make mechanically stacked four terminal tandem cells and obtain 20.3% efficiency. Crucially, we find that our infrared absorbing perovskite cells exhibit excellent thermal and atmospheric stability, unprecedented for Sn based perovskites. This device architecture and materials set will enable “all perovskite” thin film solar cells to reach the highest efficiencies in the long term at the lowest costs.
A low-bandgap (1.33 eV) Sn-based MA0.5 FA0.5 Pb0.75 Sn0.25 I3 perovskite is developed via combined compositional, process, and interfacial engineering. It can deliver a high power conversion efficiency (PCE) of 14.19%. Finally, a four-terminal all-perovskite tandem solar cell is demonstrated by combining this low-bandgap cell with a semitransparent MAPbI3 cell to achieve a high efficiency of 19.08%.
Semitransparent perovskite solar cells based on smooth perovskite films and ultrathin Cu (1 nm)/Au (7 nm) metal electrode demonstrate an efficiency of 16.5%. When illuminated through the semitransparent perovskite cell, a near-infrared-enhanced silicon heterojunction solar cell operates with 6.5% efficiency, leading to a total perovskite/silicon four-terminal tandem efficiency of 23.0%.
Transparent conducting materials are key elements in a wide variety of current technologies including flat panel displays, photovoltaics, organic, low-e windows and electrochromics. The needs for new and improved materials is pressing, because the existing materials do not have the performance levels to meet the ever- increasing demand, and because some of the current materials used may not be viable in the future. In addition, the field of transparent conductors has gone through dramatic changes in the last 5-7 years with new materials being identified, new applications and new people in the field. “Handbook of Transparent Conductors” presents transparent conductors in a historical perspective, provides current applications as well as insights into the future of the devices. It is a comprehensive reference, and represents the most current resource on the subject.
Metal reflectors or electrodes in contact with optoelectronic devices can induce parasitic light absorption. A low-refractive-index (low-n) layer inserted between the metal reflector and the optically active layer(s) reduces this absorption. We investigate the use of porous, nanoparticulate films as low-n layers, and fabricate silicon solar cells with nanoparticle/silver rear reflectors. We vary the porosity and thus n (between 1.1 and 1.5) of the nanoparticle films, which are deposited by a controllable aerosol spray process, and investigate their effectiveness in reducing infrared parasitic absorption in the solar cells. Optical test structures incorporating films with the highest n exhibit an internal reflectance of over 99%, matching best-in-class structures; lower-n layers should in theory perform better still but their rougher surfaces appear to induce plasmonic absorption in the overlying silver layer. No loss in open-circuit voltage or fill factor is observed when applying the best nanoparticle films in silicon heterojunction solar cells, enabling efficiencies similar to those achieved with reference cells that employ a thick indium tin oxide layer between the wafer and the rear silver electrode.
Multi-junction solar photovoltaics are proven to deliver the highest performance of any solar cell architecture, making them ideally suited for deployment in an increasingly efficiency driven solar industry. Conventional multi-junction cells reach up to 45% efficiency, but are so costly to manufacture that they are only currently useful for space and solar concentrator photovoltaics. Here, we demonstrate the first four and two-terminal perovskite-perovskite tandem solar cells with ideally matched bandgaps. We develop an infrared absorbing 1.2eV bandgap perovskite, $FA_{0.75}Cs_{0.25}Sn_{0.5}Pb_{0.5}I_3$, which is capable of delivering 13.6% efficiency. By combining this material with a wider bandgap $FA_{0.83}Cs_{0.17}Pb(I_{0.5}Br_{0.5})_3$ material, we reach initial monolithic two terminal tandem efficiencies of 14 % with over 1.75 V open circuit-voltage. We also make mechanically stacked four terminal tandem cells and obtain 18.1 % efficiency for small cells, and 16.0 % efficiency for 1cm2 cells. Crucially, we find that our infrared absorbing perovskite cells exhibit excellent thermal and atmospheric stability, unprecedented for Sn based perovskites. This device architecture and materials set will enable all perovskite thin film solar cells to reach the highest efficiencies in the long term at the lowest costs, delivering a viable photovoltaic technology to supplant fossil fuels.
Highly crystalline SnO2 is demonstrated in this study to serve as a stable and robust electron-transporting layer for high-performance perovskite solar cells. Benefiting from its high crystallinity, the relatively thick SnO2 electron-transporting layer (≈120 nm) provides respectable electron-transporting property to yield a promising power conversion efficiency (PCE, 18.8%) and over 90% of the initial PCE can retain after 30 d storage in ambient with ≈70% relative humidity.
Today's best perovskite solar cells use a mixture of formamidinium and methylammonium as the monovalent cations. With the addition of the inorganic cesium, the resulting triple cation perovskite compositions are thermally more stable, contain less phase impurities and are less sensitive to processing conditions. This enables more reproducible device performances close to ~21% and a power output of ~18% after 250 hours under operational conditions. These properties are key for the industrialization
A sputtered oxide layer enabled by a solution-processed oxide nanoparticle buffer layer to protect underlying layers is used to make semi-transparent perovskite solar cells. Single-junction semi-transparent cells are 12.3% efficient, and mechanically stacked tandems on silicon solar cells are 18.0% efficient. The semi-transparent perovskite solar cell has a T 80 lifetime of 124 h when operated at the maximum power point at 100 °C without additional sealing in ambient atmosphere under visible illumination.
A broad and expanding range of materials can be produced by atomic layer deposition at relatively low temperatures, including both oxides and metals. For many applications of interest, however, it is desirable to grow more tailored and complex materials such as semiconductors with a certain doping, mixed oxides, and metallic alloys. How well such mixed materials can be accomplished with atomic layer deposition requires knowledge of the conditions under which the resulting films will be mixed, solid solutions, or laminated. The growth and lamination of zinc oxide and tin oxide is studied here by means of the extremely surface sensitive technique of low energy ion scattering, combined with bulk composition and thickness determination, and x-ray diffraction. At the low temperatures used for deposition (150 °C), there is little evidence for atomic scale mixing even with the smallest possible bilayer period, and instead a morphology with small ZnO inclusions in a SnOx matrix is deduced. Postannealing of such laminates above 400 °C however produces a stable surface phase with a 30% increased density. From the surface stoichiometry, this is likely the inverted spinel of zinc stannate, Zn2SnO4. Annealing to 800 °C results in films containing crystalline Zn2SnO4, or multilayered films of crystalline ZnO,Zn2SnO4, and SnO2 phases, depending on the bilayer period.