arXiv subjects

Vincent M. Le Corre

Publications and source records attributed to Vincent M. Le Corre.

8 recordsLinked to original sources

arXiv2026

Single Best Fits Can Be Misleading: Resolving Common Trapping Signatures across FA--Cs Perovskites

Identifying defects responsible for non-radiative recombination in metal-halide perovskites remains challenging, with no common defect signatures established across compositions. Here, we combine fluence-dependent time-resolved photoluminescence, full Shockley--Read--Hall modelling and Bayesian posterior inference across an FA$_{1-x}$Cs$_x$PbI$_3$ compositional series. We show that trap occupation governs carrier dynamics and defect-parameter identifiability in semiconducting materials: weakly occupied states exhibit electron-capture-coefficient--trap-density degeneracies, whereas trap filling lifts them. In our perovskite systems, a non-degenerate signature $Tβ$, characterized by a strongly asymmetric $β_p/β_n$ capture-coefficient ratio, occurs across all compositions, suggesting substantial trap filling is a general feature of perovskite carrier dynamics. We further identify $Tα$ as a shared, device-performance-limiting non-radiative recombination channel, while a shallow $Tε$ signature unique to FAPbI$_3$ produces the largest steady-state non-radiative recombination rate and is consistent with the previously observed high stacking-fault density of this composition. This framework therefore provides a basis for comparing trapping signatures across different semiconducting materials at room temperature.

cond-mat.mtrl-sci↗

arXiv2024

Fully printed flexible perovskite solar modules with improved energy alignment by tin oxide surface modification

Fully printed flexible perovskite solar cells (f-PSCs) show great potential for the commercialization of perovskite photovoltaics owing to their compatibility with high-throughput roll-to-roll (R2R) production. However, the challenge remains in the deficiency in controlling interfacial recombination losses of the functional layer, causing remarkable loss of power conversion efficiency (PCE) in industrial production. Here, a fullerene-substituted alkylphosphonic acid dipole layer is introduced between the R2R-printed tin oxide electron transport layer and the perovskite active layer to reduce the energetic barrier and to suppress surface recombination at the buried interface. The resulting f-PSCs exhibit a PCE of 17.0% with negligible hysteresis, retain 95% of their initial PCE over 3000 bending cycles and achieve a T95 lifetime of 1200 h under 1 sun and 65 degreeC in nitrogen atmosphere. Moreover, the fully printed flexible perovskite solar mini-modules (f-PSMs) with a 20.25 cm2 aperture area achieve a PCE of 11.6%. The encapsulated f-PSMs retain 90% of their initial PCE after 500 h damp-heat testing at 65 degreeC and 85% relative humidity (ISOS-D3). This work marks an important progress toward the realization of efficient and stable flexible perovskite photovoltaics for commercialization.

cond-mat.mtrl-sci↗

arXiv2024

Precise Control of Process Parameters for >23% Efficiency Perovskite Solar Cells in Ambient Air Using an Automated Device Acceleration Platform

Achieving high-performance perovskite photovoltaics, especially in ambient air relies heavily on optimizing process parameters. However, traditional manual methods often struggle to effectively control the key variables. This inherent challenge requires a paradigm shift toward automated platforms capable of precise and reproducible experiments. Herein, we use a fully automated device acceleration platform (DAP) to optimize the process parameters for preparing full perovskite devices using a two-step method in ambient air. Eight process parameters that have the potential to significantly influence device performance are systematically optimized. Specifically, we delve into the impact of the dispense speed of organic ammonium halide, a parameter that is difficult to control manually, on both perovskite film and device performance. Through the targeted design of experiments, we reveal that the dispense speed significantly affects device performance primarily by adjusting the residual PbI2 content in the films. We find that moderate dispense speeds, e.g., 50 μl/s, contribute to top-performance devices. Conversely, too fast or too slow speeds result in devices with relatively poorer performance and lower reproducibility. The optimized parameter set enables us to establish a Standard Operation Procedure (SOP) for additive-free perovskite processing under ambient conditions, which yield devices with efficiencies surpassing 23%, satisfactory reproducibility, and state-of-the-art photo-thermal stability. This research underscores the importance of understanding the causality of process parameters in enhancing perovskite photovoltaic performance. Furthermore, our study highlights the pivotal role of automated platforms in discovering innovative workflows and accelerating the development of high-performing perovskite photovoltaic technologies.

physics.app-ph↗

arXiv2023

Beginner's guide to visual analysis of perovskite and organic solar cell current density-voltage characteristics

The current density-voltage characteristic (JV) is a critical tool for understanding the behaviour of solar cells. In this article, we present an overview of the key aspects of JV analysis and introduce a user-friendly flowchart that facilitates the swift identification of the most probable limiting process in a solar cell, based mainly on the outcomes of light-intensity-dependent JV measurements. The flowchart was developed through extensive drift-diffusion simulations and a rigorous review of the literature, with a specific focus on perovskite and organic solar cells. Moreover, the flowchart proposes supplementary experiments that can be conducted to obtain a more precise prediction of the primary performance losses. It therefore serves as an optimal starting point to analyse performance losses of solar cells.

cond-mat.mtrl-sci↗

arXiv2023

Bypassing the single junction limit with advanced photovoltaic architectures

In single-junction photovoltaic (PV) devices, the maximum achievable power conversion efficiency (PCE) is mainly limited by thermalization and transmission losses, because polychromatic solar irradiation cannot be matched to a single bandgap. Several concepts are being investigated to reduce these losses, such as the classical vertical multijunction cells, 'lateral' tandem cells, and multi-exciton generation in the form of photon up- and down-conversion. While in theory, efficiencies exceeding 90% are possible (Landsberg or thermodynamic limit), there are severe practical limitations in terms of processability, cost, and spectral sensitivity. Here, we present a simulation environment based on Bayesian Optimization that is able to predict and optimize the electrical performance of multi-junction architectures, both vertical and lateral, in combination with multi-exciton materials. With respect to vertical stacks, we show that by optimizing bandgap energies of multi-exciton generation (MEG) layers, double junctions can reach efficiencies beyond those of five-junction tandem devices (57%). Moreover, such combinations of MEG and double junction devices would be highly resilient against spectral changes of the incoming sunlight. We point out three main challenges for PV material science to realize such devices. With respect to lateral architectures, we show that MEG layers might allow reducing nonradiative voltage losses following the Energy Gap Law. Finally, we show that the simulation environment is able to use machine learned quantitative structure-property relationships obtained from high-throughput experiments to virtually optimise the active layer (such as, the film thickness and the donor-acceptor ratio) for a given architecture. The simulation environment thus represents an important building block towards a digital twin of PV materials.

physics.app-ph↗

arXiv2023

Cutting 'lab-to fab' short: High Throughput Optimization and Process Assessment in Roll-to-Roll Slot Die Coating of Printed Photovoltaics

Commercialization of printed photovoltaics requires knowledge of the optimal composition and microstructure of the single layers, and the ability to control these properties over large areas under industrial conditions. While microstructure optimization can be readily achieved by lab scale methods, the transfer from laboratory scale to a pilot production line ('lab to fab') is a slow and cumbersome process. Here, we show how we can optimize the performance of organic solar cells and at the same time assess process performance in a 2D combinatorial approach directly on an industrially relevant slot die coating line. This is enabled by a multi-nozzle slot die coating head allowing parameter variations along and across the web. This modification allows us to generate and analyze 3750 devices in a single coating run, varying the active layer donor:acceptor ratio and the thickness of the electron transport layer (ETL). We use Gaussian Process Regression (GPR) to exploit the whole dataset for precise determination of the optimal parameter combination. Performance-relevant features of the active layer morphology are inferred from UV-Vis absorption spectra. By mapping morphology in this way, small undesired gradients of process conditions (extrusion rates, annealing temperatures) are detected and their effect on device performance is quantified. The correlation between process parameters, morphology and performance obtained by GPR provides hints to the underlying physics, which are finally quantified by automated high-throughput drift-diffusion simulations. This leads to the conclusion that voltage losses which are observed for very thin ETL coatings are due to incomplete coverage of the electrode by the ETL, which cause enhanced surface recombination.

physics.app-ph↗

arXiv2022

Revealing the doping density in perovskite solar cells and its impact on device performance

Traditional inorganic semiconductors can be electronically doped with high precision. Conversely, there is still conjecture regarding the assessment of the electronic doping density in metal-halide perovskites, not to mention of a control thereof. This paper presents a multifaceted approach to determine the electronic doping density for a range of different lead-halide perovskite systems. Optical and electrical characterisation techniques comprising intensity-dependent and transient photoluminescence, AC Hall effect, transfer-length-methods, and charge extraction measurements were instrumental in quantifying an upper limit for the doping density. The obtained values are subsequently compared to the charge on the electrodes per unit volume at short-circuit conditions, which amounts to roughly $10^{16}$ cm$^{-3}$. This figure equals the product of the capacitance $C$ and the built-in potential $V_\mathrm{bi}$ and represents the critical limit below which doping-induced charges do not influence the device performance. The experimental results demonstrate consistently that the doping density is below this critical threshold ($<10^{12}$ cm$^{-3}$ which means $<CV_\mathrm{bi}$ per unit volume) for all common lead-based metal-halide perovskites. Nevertheless, although the density of doping-induced charges is too low to redistribute the built-in voltage in the perovskite active layer, mobile ions are present in sufficient quantities to create space-charge-regions in the active layer, reminiscent of doped pn-junctions. These results are well supported by drift-diffusion simulations which confirm that the device performance is not affected by such low doping densities.

cond-mat.mtrl-sci↗

arXiv2021

Pathways towards 30% efficient single-junction perovskite solar cells and the role of mobile ions

Perovskite semiconductors have demonstrated outstanding external luminescence quantum yields, enabling high power conversion efficiencies (PCE). However, the precise conditions to advance to an efficiency regime above monocrystalline silicon cells are not well understood. Here, we establish a simulation model that well describes efficient p-i-n type perovskite solar cells and a range of different experiments. We then study important device and material parameters and we find that an efficiency regime of 30% can be unlocked by optimizing the built-in potential across the perovskite layer by using either highly doped (10^19 cm-3), thick transport layers (TLs) or ultrathin undoped TLs, e.g. self-assembled monolayers. Importantly, we only consider parameters that have been already demonstrated in recent literature, that is a bulk lifetime of 10 us, interfacial recombination velocities of 10 cm/s, a perovskite bandgap of 1.5 eV and an EQE of 95%. A maximum efficiency of 31% is predicted for a bandgap of 1.4 eV. Finally, we demonstrate that the relatively high mobile ion density does not represent a significant barrier to reach this efficiency regime. Thus, the results of this paper promise continuous PCE improvements until perovskites may become the most efficient single-junction solar cell technology in the near future.

cond-mat.mtrl-sci↗