Grey Christoforo | Searcharxiv

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↗

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↗