arXiv subjects

Seongrok Seo

Publications and source records attributed to Seongrok Seo.

3 recordsLinked to original sources

arXiv2026

Stable AgBiS2 near-infrared absorbers for thin film tandem photovoltaics

AgBiS2 has rapidly risen in efficiency as single-junction photovoltaics (PVs), but its potential for tandem PVs is unexplored. Herein, we perform optical modeling based on the experimental absorption spectrum of AgBiS2, revealing that, as the NIR sub-cell, efficiencies exceeding 47.9% are achievable in triple-junction tandems, superseding tandems using Pb/Sn perovskite NIR cells (35.9%). However, fulfilling this potential requires overcoming the limited transport properties of AgBiS2 nanocrystal films, which constrains film thicknesses to only 30-50 nm, severely restricting NIR response. A solution-phase ligand exchange process is herein developed, allowing one-step deposition of passivated AgBiS2 nanocrystals that maintain efficient charge-carrier extraction despite an order of magnitude increase in film thickness. These films enable 24.0%-efficient four-terminal tandems with visible-light-absorbing lead-halide perovskite sub-cells, and monolithic tandems successfully demonstrating voltage addition. AgBiS2 PVs have high stability, retaining >90% of the original efficiency after 3 months of storage in dry air without encapsulation. This work establishes the significant potential of AgBiS2 as a stable and scalable NIR absorber for tandem PVs.

cond-mat.mtrl-sci↗

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↗

arXiv2024

Diamine Surface Passivation and Post-Annealing Enhance Performance of Silicon-Perovskite Tandem Solar Cells

We show that the use of 1,3-diaminopropane (DAP) as a chemical modifier at the perovskite/electron-transport layer (ETL) interface enhances the power conversion efficiency (PCE) of 1.7 eV bandgap FACs mixed-halide perovskite single-junction cells, primarily by boosting the open-circuit voltage (VOC) from 1.06 V to 1.15 V. Adding a post-processing annealing step after C60 evaporation, further improves the fill factor (FF) by 20% from the control to the DAP + post-annealing devices. Using hyperspectral photoluminescence microscopy, we demonstrate that annealing helps improve compositional homogeneity at the top and bottom interfaces of the solar cell, which prevents detrimental bandgap pinning in the devices and improves C60 adhesion. Using time-of-flight secondary ion mass spectrometry, we show that DAP reacts with formamidinium present near the surface of the perovskite lattice to form a larger molecular cation, 1,4,5,6-tetrahydropyrimidinium (THP) that remains at the interface. Combining the use of DAP and the annealing of C60 interface, we fabricate Si-perovskite tandems with PCE of 25.29%, compared to 23.26% for control devices. Our study underscores the critical role of chemical reactivity and thermal post-processing of the C60/Lewis-base passivator interface in minimizing device losses and advancing solar-cell performance of wide-bandgap mixed-cation mixed-halide perovskite for tandem application.

cond-mat.mtrl-sci↗