Photovoltaics Research at NREL
General overview of NREL research, including scaling to terawatt PV, reliability testing, DuraMAT, perovskites, silicon PV, CdTe, III-V, and tandems.
CdTe↗
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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Techno-economic Analysis of Novel PV Plant Designs for Extreme Cost Reductions
A techno-economic analysis is underway examining the cost and performance of future large-scale photovoltaic (PV) plant components, including bifacial modules, tandem modules, increased plant voltage architectures, and module-level power electronics. Integration of these components into PV plant designs is compared with current PV technologies based on levelized cost of electricity (LCOE). Baseline models are developed and validated against recorded PV plant performance data. Expected cost and performance data of future PV technologies are incorporated into the baseline models. An evolutionary algorithm is utilized to optimize PV plant configuration, technology combination, and LCOE. This paper focuses on the bifacial module analysis.
14 SOLAR ENERGY↗
PVcircuit [SWR-22-26]
The software contains objects that are building blocks for PV modeling and interactive data fitting based on: Optoelectronic models for tandem/multijunction solar cells including resistive and luminescent coupling; simulation of modules composed of 2T, 3T, and 4T tandem solar cells; and energy yield analysis of PV systems composed of tandem solar cells.
Geisz, John↗
PVcircuit v0.0.6 [SWR-22-26]
The software contains objects that are building blocks for PV modeling and interactive data fitting based on: Optoelectronic models for tandem/multijunction solar cells including resistive and luminescent coupling; simulation of modules composed of 2T, 3T, and 4T tandem solar cells; and energy yield analysis of PV systems composed of tandem solar cells.
Geisz, John↗
Cost Assessment of Future Tandem Perovskite-Silicon Modules and LCOE Comparison to Silicon Technologies in Europe
Tandem perovskite-silicon (TPS) photovoltaic (PV) technology is a promising pathway for achieving higher efficiencies than those of single-junction crystal-silicon (c-Si) technologies. In this work, a techno-economic assessment of a TPS module is performed considering a viable large-scale manufacturing process for two future scenarios in 2025 and 2030 which allowed us to identify the main cost drivers of the tandem module cost. Furthermore, to analyse the performance of tandem module-based utility-scale PV systems and understand their competitiveness in Europe, the levelized cost of electricity was compared to passivated emitter and rear cell as well as silicon heterojunction based PV systems. The aim of this work is to provide a cost and performance guidance for TPS modules which could contribute to future PV energy systems.
ENERGY PLANNING, POLICY, AND ECONOMY,SOLAR ENERGY↗
Choose Your Own Adventure: Fabrication of Monolithic All-Perovskite Tandem Photovoltaics
Metal halide perovskites (MHPs) have transfixed the photovoltaic (PV) community due to their outstanding and tunable optoelectronic properties coupled to demonstrations of high-power conversion efficiencies (PCE) at a range of bandgaps. This has motivated the field to push perovskites to reach the highest possible performance. One way to increase the efficiency is by fabricating multijunction solar cells, which can split the solar spectrum, reducing thermalization loss. Low-cost all-perovskite tandems have a real chance to soon exceed 30% PCE, which could transform the PV industry. Achieving this goal requires the identification of perovskite sub-cells that are both highly efficient and can be effectively integrated. In this review, it is discussed how to navigate the multiple-choice adventure in choosing between the myriad of options and considerations present when deciding what perovskite materials, contact layers, and processing tools to use. Some of the potential fabrication pitfalls often encountered in MHP based tandem PVs are highlighted, so that they can hopefully be avoided in the future.
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Device Performance of Emerging Photovoltaic Materials (Version 2)
Following the 1st release of the "Emerging photovoltaic (PV) reports", the best achievements in the performance of emerging photovoltaic devices in diverse emerging photovoltaic research subjects are summarized, as reported in peer-reviewed articles in academic journals since August 2020. Updated graphs, tables, and analyses are provided with several performance parameters, e.g., power conversion efficiency, open-circuit voltage, short-circuit current density, fill factor, light utilization efficiency, and stability test energy yield. These parameters are presented as a function of the photovoltaic bandgap energy and the average visible transmittance for each technology and application and are put into perspective using, e.g., the detailed balance efficiency limit. The 2nd installment of the "Emerging PV reports" extends the scope toward tandem solar cells and presents the current state-of-the-art in tandem solar cell performance for various material combinations.
36 MATERIALS SCIENCE↗
Historical and Future Learning for the New Era of Multi-Terawatt Photovoltaics
Solar photovoltaics (PV) is entering a new era of multi-terawatt deployment, with 2 TW already in service and more than 75 TW predicted in many scenarios by 2050. This next era has been enabled by over five decades of cumulative advances in PV module cost reduction, performance and reliability. The current scale of deployment also introduces new needs, opportunities and challenges. In this Perspective we frame a path forwards based on learning, broadly defined as a combination of expansion of knowledge and advances through research and development, experience and collaboration. We discuss historical topics where learning has driven PV deployment until now, and emerging areas that are required to sustain high levels of future deployment. We expect progress to continue in terms of module price, performance and reliability, driven by advances in PV cell and module design, the emergence of tandem devices and increased focus on extending module lifetimes. Large-scale deployment also means large-scale sustainability and responsibility. We therefore posit that additional metrics, such as the impact on global CO2 emissions, resource consumption and design for reuse and recycling, will become increasingly important to the PV industry and provide opportunities for further learning.
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Tandem Photovoltaics Core Program Final Technical Report
The Tandem Photovoltaics Core Program was a multi-year initiative aimed at advancing hybrid tandem solar cell technologies to enhance solar module efficiency beyond the limits of single junction devices. This project focused on the development, testing, and scaling of prototype photovoltaic devices, with the goal of achieving commercial relevance and driving industry adoption. The work was divided into three tasks: 1) Comparative Analysis of Tandem Technologies: This task focused on quantifying energy yield under real-world conditions and assessing economic viability of tandems relative to silicon-based modules. The project's modeling framework incorporated performance data, cost of materials, and manufacturing process impacts to optimize tandem designs 2) Tandem Integration and Prototyping: In this task, we developed innovative tandem designs by combining metal halide perovskite (MHP) top cells and silicon (Si) bottom cells. The project focuses on both mechanical integration and direct deposition techniques to enable compatibility with commercially relevant Si technologies, such as passivated contact or PERC cells. 3) Scale-up and Reliability: This task addressed the challenges of large-area fabrication by developing scalable deposition methods and robust interconnection schemes for tandems. The project looked at different accelerated testing such as thermal cycling, damp heat exposure, and potential induced degradation, to ensure long-term stability of devices in field conditions. Tandem solar cells can greatly increase module efficiency beyond conventional single junction (SJ) devices, which are approaching their theoretical limit. There are many ways to fabricate a tandem cell or module in terms of materials used, configuration, and terminal connection. This SETO core project focused critical factors in enabling tandems to enter the market, including hardware integration, technoeconomic analysis (TEA), and energy yield analysis. We focused on MHP/Si hybrid tandem solar cells and modules as a model system for their versatility in module design comparisons, providing valuable insights for other tandem options. While champion cells with areas <1cm2 are regularly demonstrated by groups around the world, it is significantly more challenging to translate these advances into modules, and fewer institutions and companies are working at the module level. This project addressed questions about module fabrication, testing, and reliability that are hard to answer without actually fabricating prototypes. We also performed analysis and road-mapping activities to understand the potential for a wider variety of tandems, including all-perovskite tandems fabricated in collaboration with the Perovskite PV core program. Detailed technical results from this project are described for each task in Section 7.
14 SOLAR ENERGY↗
GaAsP/Si Tandem Solar Cells: Pathway to Low-Cost, High-Efficiency Photovoltaics
Si is the dominant PV technology, now and for the foreseeable future, due to its extensive manufacturing infrastructure, supply chain, feedstock availability, and highly optimized degree of fabrication processes, which altogether has produced an economic scenario where PV electricity generation is often cheaper than conventional fossil based generation. In many places, the overarching goal of grid parity has been achieved, but further improvement in performance-cost metrics are still needed to sustain the continued LCOE reductions needed to not only compete with conventional generation, but displace it on a global scale; a matter of critical importance if we stand any hope of slowing climate change. Nevertheless, single-junction Si PV is already nearing its physical limit, both in performance and cost, and is thus cannot meet these long-term goals alone. To this end, we are working on the development of monolithic III-V/Si tandem solar cells, which improve upon the performance of pure Si by providing enhanced utilization (reduced thermalization) of high-energy photons. This architecture nominally combines the substantial existing knowledge base, manufacturing infrastructure, and low cost of Si PV with the high efficiencies afforded by the well-established multijunction approach — the only proven way to break the single-junction limit. Although the metal-halide perovskite/Si tandem architecture has garnered substantial attention in recent years, serious questions regarding reliability and service lifetime remain, whereas III-V PV has a proven track record, including in the harsh concentrator and space environments. Additionally, there are multiple fabrication approaches to producing III-V/Si tandem cells, but we are focused on monolithic epitaxial integration as it is the most likely to yield the lowest ultimate LCOE in a fully mature, scaled technology. In this work we have produced multiple generations of GaAsP/Si tandem solar cells, demonstrating a more than 10% absolute AM1.5G efficiency improvement within the time frame of the project, including two verified world records. We have done this using industry-standard fabrication methods, showing that this platform can ultimately be manufactured at scale using existing or only slightly upgraded Si and III-V tooling. Our scientific and engineering advances across a range of fundamental and applied areas – III-V/Si heteroepitaxial integration, defect control in metamorphic III-V epitaxy, fundamental materials-oriented solar cell design and modeling methodology, and more – have created clear pathways for continued advances toward the goal of >30% AM1.5G cell efficiency (and >25% module) and will serve to inform the broader research community for well beyond this immediate application. Techno-economic modeling indicates that our approach can indeed meet SunShot/SETO LCOE targets, but as with any “post-Si” technology there are difficult, but not insurmountable barriers, requiring continued focused research and development efforts.
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Bandgap engineering of SrZrS 3 chalcogenide perovskite via substitutional doping for photovoltaic applications: a first-principles DFT study
Strontium zirconium sulfide (SrZrS 3 ) has garnered significant attention for photovoltaic (PV) applications due to its excellent optoelectronic properties, high chemical and moisture stability, and non-toxicity. However, the bandgaps of both the α- and β-phases lie outside the optimum ranges for both single-junction solar cells (SJSCs) and tandem solar cells (TSCs), thereby limiting their applications in PV technologies. In this study, we employed hybrid density functional theory to engineer the band gaps of α- and β-SrZrS 3 through substitutional doping. We considered three dopants (Hf, Sn, and Ti) at the Zr site of SrZrS 3 with varying doping concentrations and investigated their effects on the structural, electronic, and optical properties of the materials. We found that Sn and Ti doping effectively lowers the band gaps of both α- and β-SrZrS 3 , whereas Hf doping increases them. For x values up to 0.25, the band gaps of the α-SrZr 1−x Sn x S 3 and α-SrZr 1−x Ti x S 3 are within the optimum range for SJSCs, and those of β-SrZr 1−x Sn x S 3 and β-SrZr 1−x Ti x S 3 lie within the optimum range for Si/perovskite as well as perovskite/perovskite TSCs. The three dopants exhibited significant effects on the optical properties of both α- and β-SrZrS 3 , including the absorption coefficient, energy-loss functions, reflectivity, and refractivity spectra. Thermodynamic stability analysis revealed that for both phases, SrZr 1−x Hf x S 3 can be synthesized via exothermic processes, whereas the formation of SrZr 1−x Ti x S 3 and SrZr1−xSn x S 3 is endothermic and hence, not thermodynamically favorable. Further analysis showed that SrZr 1−x Ti x S 3 in both α- and β-phases are stable under thermodynamic equilibrium conditions, whereas SrZr 1−x Sn x S 3 is prone to dissociation into ternary phases (SrZrS 3 and SrSnS 3 ), especially at higher doping concentrations. These results show that Ti doping is effective in tuning the band gaps of α- and β-SrZrS 3 toward the optimal values for PV applications.
14 SOLAR ENERGY↗
Advances in Mixed Tin‐Lead Narrow‐Bandgap Perovskites for Single‐Junction and All‐Perovskite Tandem Solar Cells
Abstract Organic–inorganic metal‐halide perovskites have received great attention for photovoltaic (PV) applications owing to their superior optoelectronic properties and the unprecedented performance development. For single‐junction PV devices, although lead (Pb)‐based perovskite solar cells have achieved 26.1% efficiency, the mixed tin‐lead (Sn‐Pb) perovskites offer more ideal bandgap tuning capability to enable an even higher performance. The Sn‐Pb perovskite (with a bandgap tuned to ≈1.2 eV) is also attractive as the bottom subcell for a tandem configuration to further surpass the Shockley–Queisser radiative limit for the single‐junction devices. The performance of the all‐perovskite tandem solar cells has gained rapid development and achieved a certified efficiency up to 29.1%. In this article, the properties and recent development of state‐of‐the‐art mixed Sn‐Pb perovskites and their application in single‐junction and all‐perovskite tandem solar cells are reviewed. Recent advances in various approaches covering additives, solvents, interfaces, and perovskite growth are highlighted. The authors also provide the perspective and outlook on the challenges and strategies for further development of mixed Sn‐Pb perovskites in both efficiency and stability for PV applications.
14 SOLAR ENERGY↗
High-Photovoltage All-Perovskite Tandem Solar Cells for Photovoltaic-Electrolysis Water-Splitting Applications
Monolithic perovskite/perovskite tandem solar cells have attracted substantial attention owing to their promise for high power conversion efficiency (PCE) and low fabrication cost. Conventional all-perovskite tandem solar cells employ a mixed tin (Sn)-lead (Pb) low-bandgap subcell, which suffers from instability issues in the ambient air. Here, we fabricate two-terminal perovskite/perovskite tandem solar cells consisting of two solution-processed perovskite subcells based on the more airstable pure Pb-based perovskites. The champion perovskite tandem cell exhibits a PCE of 19.2% with a high open-circuit voltage of 2.15 V. We further demonstrate photovoltaicelectrolysis (PV-EC) water-splitting applications using these high-photovoltage all-perovskite tandem solar cells.
metal halide perovskite↗
Photovoltaics Based on Direct and Indirect Gap Semiconductors
Direct and thin, or indirect and thick absorbers can yield cells close to 30% but there are practical limits due to defects, cost, reliability. Tandems and new ideas are needed to minimize thermalization and entropy losses and to enable high absorptance in thin Si layers. Direct-gap absorbers have ~1000x higher recombination losses than Si, but being 100x thinner, the limiting 1-sun efficiencies are similar due to 100x higher G.
direct-gap↗
Interfacial Connections between Organic Perovskite/n + Silicon/Catalyst that Allow Integration of Solar Cell and Catalyst for Hydrogen Evolution from Water
Abstract The rapidly increasing solar conversion efficiency (PCE) of hybrid organic–inorganic perovskite (HOIP) thin‐film semiconductors has triggered interest in their use for direct solar‐driven water splitting to produce hydrogen. However, application of these low‐cost, electronic‐structure‐tunable HOIP tandem photoabsorbers has been hindered by the instability of the photovoltaic‐catalyst‐electrolyte (PV+E) interfaces. Here, photolytic water splitting is demonstrated using an integrated configuration consisting of an HOIP/n + silicon single junction photoabsorber and a platinum (Pt) thin film catalyst. An extended electrochemical (EC) lifetime in alkaline media is achieved using titanium nitride on both sides of the Si support to eliminate formation of insulating silicon oxide, and as an effective diffusion barrier to allow high‐temperature annealing of the catalyst/TiO 2 ‐protected‐n + silicon interface necessary to retard electrolytic corrosion. Halide composition is examined in the (FA 1‐x Cs x )PbI 3 system with a bandgap suitable for tandem operation. A fill factor of 72.5% is achieved using a Spiro‐OMeTAD‐hole‐transport‐layer (HTL)‐based HOIP/n + Si solar cell, and a high photocurrent density of −15.9 mA cm −2 (at 0 V vs reversible hydrogen electrode) is attained for the HOIP/n + Si/Pt photocathode in 1 m NaOH under simulated 1‐sun illumination. While this thin‐film design creates stable interfaces, the intrinsic photo‐ and electro‐degradation of the HOIP photoabsorber remains the main obstacle for future HOIP/Si tandem PEC devices.
08 HYDROGEN↗
How Useful are Conventional I–Vs for Performance Calibration of Single- and Two-Junction Perovskite Solar Cells? A Statistical Analysis of Performance Data on ≈200 Cells from 30 Global Sources
As perovskite photovoltaics (PV) advance from the laboratory to commercial prototypes, their accurate and reliable performance testing is becoming increasingly important. The well-documented dynamic response of perovskite solar cells to an external applied voltage has led to the development of steady-state performance measurement methods; however, these methods have not been widely adopted by the perovskite PV community. A key reason for this is that steady-state measurement methods take tens of minutes to complete, as opposed to conventional "fast" current-voltage (I-V) measurements usually lasting a few seconds. Fast I-Vs arise from a snapshot, almost always not a steady-state condition of the device; however, given their widespread use, the question arises: how do performance parameters of perovskite PV compare when measured with fast I-V and with a steady-state method? Results compiled from approximately 200 perovskite PV cells, including single junction, and two-terminal perovskite-perovskite and perovskite-Si tandems, show that fast I-Vs can provide a useful measure of the open-circuit voltage of the devices, while the short-circuit current and the overall efficiency can be widely misestimated. Here, the implications of these findings on performance testing protocols are discussed and possible options for fast and accurate testing of perovskite PV are proposed.
14 SOLAR ENERGY↗
Leaving in the lead: Priorities for perovskite photovoltaics
The need for moving electricity generation to a sustainable model requires the development of low cost ubiquitous photovoltaics (PVs) to harvest the planet’s primary energy source, the Sun. Building upon the successes of Si-based and CdTe-based PV technologies, PVs with lower-embodied energy and requiring lower carbon dioxide equivalent to produce will be required to meet long-term sustainability goals. In particular, thin-film technologies, such as high-efficiency metal halide perovskite (MHP) PV modules, provide avenues to reduced embodied energy, lower energy payback times, and enabling energy-dense tandems [H. M. Wikoff et al., Joule 6(7), 1710–1725 (2022) and V. Fthenakis, Renewable Sustainable Energy Rev. 13(9), 2746–2750 (2009)]. The ability to improve efficiency and lower energy payback time of next generation thin-film PV modules is a critical foundation for green H2 and electrification more broadly. In this regard, Pb-based MHP-PVs have separated themselves as a result of the high-efficiencies that can be realized across a range of electronic gaps. Questions regarding Pb-based MHP-PVs that are often asked, as the challenges of efficiency and reliability are met, revolve around the “problem” of the Pb content. Specifically, “does Pb toxicity preclude MHP-PV modules from being deployed at the TW scale?” To provide this sense of scale, in 2021, the United States burned 10.5 quads of coal, with 90% of that used for electricity generation. Given the energy content of coal of 29 MJ/kg and a residual lead content in that coal of 30 mg/kg, electricity generation from coal resulted in more lead emitted into the atmosphere than what would be required to produce over 2 TW of MHP-PV name plate capacity (assuming a 20% module efficiency and an ∼700 nm active layer). This amounts to more PV power than has been deployed across all PV technologies and geographies to date. This only includes US coal consumption; the rest of the world would be much larger. This example illustrates the scale of the material usage relative to the energy production. Imagine a power-generation technology that offsets these Pb emissions from coal and essentially sequesters this Pb content between two sheets of impermeable glass. Why should we let Pb’s history of misuse prevent it from being included in next generation PV modules that can enable a sustainable energy future?
14 SOLAR ENERGY↗
Novel Chalcopyrites for Advanced Photoelectrochemical Water Splitting
With the support of DoE’s EERE office, our team has established a unique tool-chest of capabilities, including theoretical modeling (Lawrence Livermore National Laboratory: LLNL), state-of-the-art synthesis (Hawaii Natural Energy Institute: HNEI, Stanford, and the National Renewable Energy Laboratory: NREL) and advanced materials and interfaces characterization (University of Nevada, Las Vegas: UNLV, and Lawrence Berkeley National Laboratory: LBNL), to accelerate the development of high efficiency and durable chalcopyrite materials for advanced photoelectrochemical (PEC) water splitting. Using this synergistic approach, we have successfully created new wide bandgap chalcopyrite photocathodes generating over 10 mA/cm 2 , developed innovative strategies to protect them from corrosion, and engineered novel integration methods to circumvent thin film materials mechanical, chemical and thermal incompatibility. In Task 1 “Modeling and synthesis of chalcopyrite photocathodes”, we expanded our library of wide bandgap chalcopyrites for PEC water splitting. With support from LLNL’s “Computational Materials Diagnostics and Optimization of PEC Devices”, LBNL’s “photophysical” and NREL’s “I-III-VI Compound Semiconductors for Water-Splitting” nodes, we investigated two new chalcopyrite candidates for PEC water splitting: Cu(In,Al)Se 2 and Cu(In,B)Se 2 . We also further developed ordered vacancy compounds, such as CuGa 3 Se 5 , with unprecedented durability during PEC waters splitting in acidic solutions. In Task 2 “Interfaces engineering for enhanced efficiency and durability”, we addressed both the non-ideal band-edge positions of chalcopyrites with respect to water redox potentials, as well as their chemical instability under PEC water splitting, with a buried-junctions approach. With help from NREL’s “High-Throughput Experimental Thin Film Combinatorial Capabilities” and “Corrosion Analysis of Materials” nodes, we engineered environmentally friendly n-type buffers, including Mn x Zn 1-x O, to adjust the chalcopyrite band-edge positions and achieved photovoltages as high as 925 mV. Also, we integrated non-precious catalytic-protecting layers, such as WO 3 , to enhance the water splitting long-term stability of chalcopyrite absorbers. Finally, in Task 3 “Hybrid photoelectrode device integration”, we proposed an innovative method to bond wide bandgap photocathodes onto narrow bandgap PV drivers at room temperature using conductive polymers. Our semi-monolithic approach addressed fundamental processing incompatibility issues, as both the photocathode and the PV driver are processed separately. Proof-of-concept whole-chalcopyrite tandems were obtained by consecutive exfoliation and transfer of fully integrated 1.85 eV CuGa 3 Se 5 and 1.13 eV CuInGaSe 2 stacks from their Mo/SLG substrates onto a new single FTO host substrate.
08 HYDROGEN↗