Universal Current Losses in Perovskite Solar Cells Due to Mobile Ions
Advanced Energy Materials (2021)
Abstract:
Efficient mixed metal lead-tin halide perovskites are essential for the development of all-perovskite tandem solar cells, however they are currently limited by significant short-circuit current losses despite their near optimal bandgap (≈1.25 eV). Herein, the origin of these losses is investigated, using a combination of voltage dependent photoluminescence (PL) timeseries and various charge extraction measurements. It is demonstrated that the Pb/Sn-perovskite devices suffer from a reduction in the charge extraction efficiency within the first few seconds of operation, which leads to a loss in current and lower maximum power output. In addition, the emitted PL from the device rises on the exact same timescales due to the accumulation of electronic charges in the active layer. Using transient charge extraction measurements, it is shown that these observations cannot be explained by doping-induced electronic charges but by the movement of mobile ions toward the perovskite/transport layer interfaces, which inhibits charge extraction due to band flattening. Finally, these findings are generalized to lead-based perovskites, showing that the loss mechanism is universal. This elucidates the negative role mobile ions play in perovskite solar cells and paves a path toward understanding and mitigating a key loss mechanism.
Understanding and Minimizing VOC Losses in All-Perovskite Tandem Photovoltaics
Adv. Energy Mater. 2022, 2202674
Abstract:
Understanding performance losses in all-perovskite tandem photovoltaics is crucial to accelerate advancements toward commercialization, especially since these tandem devices generally underperform in comparison to what is expected from isolated layers and single junction devices. Here, the individual sub-cells in all-perovskite tandem stacks are selectively characterized to disentangle the various losses. It is found that non-radiative losses in the high-gap subcell dominate the overall recombination in the baseline system, as well as in the majority of literature reports. Through a multi-faceted approach, the open-circuit voltage (VOC) of the high-gap perovskite subcell is enhanced by 120 mV. Employing a novel (quasi) lossless indium oxide interconnect, this enables all-perovskite tandem solar cells with 2.00 V VOC and 23.7% stabilized efficiency. Reducing transport losses as well as imperfect energy-alignments boosts efficiencies to 25.2% and 27.0% as identified via subcell selective electro- and photo-luminescence. Finally, it is shown how, having improved the VOC, improving the current density of the low-gap absorber pushes efficiencies even further, reaching 25.9% efficiency stabilized, with an ultimate potential of 30.0% considering the bulk quality of both absorbers measured using photo-luminescence. These insights not only show an optimization example but also a generalizable evidence-based optimization strategy utilizing optoelectronic sub-cell characterization.
Impact of Ion Migration on the Performance and Stability of Perovskite‐Based Tandem Solar Cells
Advanced Energy Materials Wiley (2024)
Roadmap on established and emerging photovoltaics for sustainable energy conversion
Journal of Physics Energy IOP Publishing (2024)
Abstract:
<jats:title>Abstract</jats:title> <jats:p>Photovoltaics (PVs) are a critical technology for curbing growing levels of anthropogenic greenhouse gas emissions, and meeting increases in future demand for low-carbon electricity. In order to fulfil ambitions for net-zero carbon dioxide equivalent (CO<jats:sub>2</jats:sub>eq) emissions worldwide, the global cumulative capacity of solar PVs must increase by an order of magnitude from 0.9 TW<jats:sub>p</jats:sub> in 2021 to 8.5 TW<jats:sub>p</jats:sub> by 2050 according to the International Renewable Energy Agency, which is considered to be a highly conservative estimate. In 2020, the Henry Royce Institute brought together the UK PV community to discuss the critical technological and infrastructure challenges that need to be overcome to address the vast challenges in accelerating PV deployment. Herein, we examine the key developments in the global community, especially the progress made in the field since this earlier roadmap, bringing together experts primarily from the UK across the breadth of the photovoltaics community. The focus is both on the challenges in improving the efficiency, stability and levelized cost of electricity of current technologies for utility-scale PVs, as well as the fundamental questions in novel technologies that can have a significant impact on emerging markets, such as indoor PVs, space PVs, and agrivoltaics. We discuss challenges in advanced metrology and computational tools, as well as the growing synergies between PVs and solar fuels, and offer a perspective on the environmental sustainability of the PV industry. Through this roadmap, we emphasize promising pathways forward in both the short- and long-term, and for communities working on technologies across a range of maturity levels to learn from each other.</jats:p>Ion-induced field screening as a dominant factor in perovskite solar cell operational stability
Nature Energy Nature Research 9:6 (2024) 664-676