arXiv subjects

Henry Snaith

Publications and source records attributed to Henry Snaith.

4 recordsLinked to original sources

arXiv2026

Deriving a comprehensive dataset of optical constants for metal halide perovskites

Accurate optical constants are essential for modelling light propagation, absorption, and ultimately photovoltaic performance in state of the art perovskite solar cells and is especially important for multiple junction or tandem cells. However, available datasets for metal halide perovskites remain sparse, inconsistent in quality, and often suffer from unphysical sub bandgap extinction caused by surface roughness and limitations of conventional ellipsometry fits. Here, we present a comprehensive library of complex refractive indices (n,k) for a technologically relevant set of FA based lead perovskites, spanning bromide compositions from 0 to 100 percent, and mixed Pb Sn perovskites with Sn fractions from 0 to 60 %. Using state of the art fabrication protocols that yield high quality films, we combine variable angle spectroscopic ellipsometry measurements with highly sensitive sub bandgap probes, including photothermal deflection spectroscopy for neat lead based perovskites and Fourier transform photocurrent spectroscopy for Pb Sn alloys, to reconstruct fully zeroed dielectric functions across and below the band edge. The measured data are then stitched and recalculated via a Kramers Kronig consistent framework, ensuring physically accurate behaviour across the full spectral range. Finally, we introduce a transformation based interpolation scheme that preserves spectral shape and feature alignment, enabling reliable determination of (n,k) for any intermediate composition or band gap. This complete dataset and interpolation protocol provide a standardized foundation for optical modelling of perovskite and tandem solar cells, addressing longstanding data gaps and supporting accurate simulations of next generation photovoltaic architectures.

cond-mat.mtrl-sci↗

arXiv2025

Trion Formation Hampers Single Quantum Dot Performance in Silane-Coated FAPbBr3 Quantum Dots

We explore silane-coated formamidinium lead bromide (FAPbBr3) quantum dots as single photon emitters and compare them to FAPbBr3 quantum dots passivated with a phosphoethylammonium derivative (PEAC8C12), which represents current state-of-the-art in zwitterionic molecular surface ligand passivation. We compare properties including single-photon purity (g2(t)), linewidth, blinking, and photostability. We find that at room temperature, these silane-coated dots perform comparably to the PEAC8C12 passivation in terms of single-photon performance metrics, while exhibiting improvements in photostability. However, we find that at 4K, silane-coated FAPbBr3 quantum dots perform worse than the PEAC8C12-passivated samples, exhibiting faster blue-shifting and photobleaching under illumination. Analysis of fluorescence lifetime intensity distributions from the photon-counting data indicates increased efficiency of fast non-radiative processes in the silane-coated quantum dots at 4K. We propose a trion related degradation pathway at low temperatures that is consistent with the observed kinetics and estimate that at 4K with 6.1 uJ/cm2, 472 nm excitation the silane-coated quantum dots build up double the trion population of their PEAC8C12-passivated counterparts.

cond-mat.mtrl-sci↗

arXiv2023

Architecture Optimization Dramatically Improves Reverse Bias Stability in Perovskite Solar Cells: A Role of Polymer Hole Transport Layers

We report that device architecture engineering has a substantial impact on the reverse bias instability that has been reported as a critical issue in commercializing perovskite solar cells. We demonstrate breakdown voltages exceeding -15 V in typical pin structured perovskite solar cells via two steps: i) using polymer hole transporting materials; ii) using a more electrochemically stable gold electrode. While device degradation can be exacerbated by higher reverse bias and prolonged exposure, our as-fabricated perovskite solar cells completely recover their performance even after stressing at -7 V for 9 hours both in the dark and under partial illumination. Following these observations, we systematically discuss and compare the reverse bias driven degradation pathways in perovskite solar cells with different device architectures. Our model highlights the role of electrochemical reaction rates and species in dictating the reverse bias stability of perovskite solar cells.

physics.chem-ph↗

arXiv2016

Microseconds, milliseconds and seconds: deconvoluting the dynamic behaviour of planar perovskite solar cells

Perovskite solar cells (PSC) are shown to behave as coupled ionic-electronic conductors with strong evidence that the ionic environment moderates both the rate of electron-hole recombination and the band offsets in planar PSC. Numerous models have been presented to explain the behavior of perovskite solar cells, but to date no single model has emerged that can explain both the frequency and time dependent response of the devices. Here we present a straightforward coupled ionic-electronic model that can be used to explain the large amplitude transient behavior and the impedance response of PSC.

cond-mat.mtrl-sci↗