Ruy Sebastian Bonilla

The development of In‐free transparent conductive oxides (TCOs) is essential for sustainable photovoltaics. For undoped tin oxide (SnO _x ), achieving high conductivity requires precise control over intrinsic defect chemistry. This work explores the impact of deposition pressure and oxygen stoichiometry on the electrical and optical properties of SnO _x films grown by pulsed laser deposition (PLD). We identify a narrow conductivity window achieved at oxygen pressures between 0.015 and 0.020 mbar, beyond which a substantial drop in conductivity is observed. Within this optimal window, the SnO _x films exhibit a 3‐fold mobility enhancement after 300°C air annealing, despite preserving an amorphous phase. This improvement is primarily attributed to the reduction of ionized impurity scattering, evidenced by a simultaneous decrease in free carrier density. To demonstrate functionality, the inherent soft‐landing nature of PLD was exploited to preserve the passivation quality of textured tunnel oxide passivating contacts (TOPCon) silicon substrates, as implied open‐circuit voltage (iV _oc ) mapping confirmed the absence of deposition‐induced damage. Finally, we demonstrate the compatibility of this In‐free TCO by fabricating proof‐of‐concept perovskite solar cells on textured SnO _x /n‐TOPCon substrates, achieving open‐circuit voltage of 1.21 V. These results highlight the potential of SnO _x for integration as an interconnection layer in fully textured perovskite/Si tandem solar cells.

Transparent conducting oxides (TCOs) are essential for the optoelectronics industry, but there is a critical gap in cost‐effective methods to rapidly deposit low‐sheet‐resistance, high‐transmittance films without damaging delicate materials, including emerging soft semiconductors like metal‐halide perovskites. In this work, atmospheric pressure chemical vapor deposition (AP‐CVD) is used to synthesize H:In ₂ O ₃ films with 7.20 ± 0.01 Ω □ ⁻¹ sheet resistance (0.50 ± 0.06 mΩ cm resistivity) and transmittance up to 89% in the near‐infrared (NIR), surpassing commercial sputter‐deposited indium tin oxide. The growth rate is 40 higher than atomic layer deposition (ALD), and the AP‐CVD films are fully processed under atmospheric conditions at only 140 °C. Comparison of secondary ion mass spectrometry and time‐of‐flight elastic recoil detection analysis with changes in carrier concentration indicates that H dopants are introduced from the water oxidant. There is an increase in mobility from 40 ± 10 cm ² V ⁻¹ s ⁻¹ to 160 ± 30 cm ² V ⁻¹ s ⁻¹ when changing from O ₂ to H ₂ O as the oxidant, which is attributed to hydrogen‐mediated passivation of defect‐related electronic states that would otherwise act as carrier scattering centers. This work establishes AP‐CVD as a promising method for manufacturing high figure‐of‐merit TCOs in a rapid, scalable, and cost‐effective manner, using mild growth conditions compatible with thermally‐sensitive materials.

Doping two-dimensional (2D) semiconductors without direct chemical or structural modification of the channel remains a central challenge for device integration. Here we demonstrate an electrostatic doping strategy on monolayer MoS2 based on embedding fixed charge in engineered dielectric stacks, enabling carrier modulation in the absence of volatile external bias. By comparing different dielectric architectures, we show that effective electrostatic doping is governed by the defect landscape of the capping dielectrics and their interface with the 2D channel. A self-consistent electrostatic model reveals that interface states control the partitioning of the dielectric embedded charge between carriers trapped in defects or free for conduction in the channel, posing limits to the effectiveness of electrostatic coupling. This work establishes electrostatic doping as a viable strategy for carrier modulation in 2D semiconductors and identifies dielectric defect engineering as central to its implementation.

Indium-based transparent conductive oxides are widely used as electrodes and recombination layers in perovskite/silicon tandem solar cells, yet their scalability is constrained by indium scarcity and sputtering-induced damage. We report high-efficiency and stable indium-free perovskite/silicon tandem solar cells enabled by reactive plasma deposited tin oxide (RPD-SnO _x ). For RPD-SnO _x as the recombination layer, we achieved a certified efficiency of 33.6%. Fully indium-free tandems that used RPD-SnO _x as both recombination layer and electrodes delivered a champion power conversion efficiency of 33.2% (1 square centimeter) and a minimodule with a certified efficiency of 31.0% (207.9 square centimeters). Dense and uniform self-assembled monolayer anchoring enabled by RPD-SnO _x suppressed nonradiative recombination and reduced halide migration. Indium-free minimodules exhibited high thermal, damp-heat, and outdoor operational stability and retained 65% of their maximum initial efficiency after 105 days of outdoor operation.

As Europe progresses toward a greener future, the years ahead bring expectations of widespread, large-scale photovoltaic (PV) deployment. Presently, mainstream silicon PV is transitioning away from the passivated emitter rear cell (PERC) architecture towards higher efficiency cell designs: tunnel oxide passivated contact (TOPCon) and silicon heterojunction (SHJ). With net-zero deadlines looming, there is an urgent need for comprehensive sustainability investigations into minimizing the environmental impact of large-scale actions before suffering avoidable consequences. Using life cycle assessment, these three silicon technologies are investigated and compared, finding SHJ to have the lowest global impact, closely followed by TOPCon. Both have lower impacts than PERC for 15 of 16 investigated environmental impact categories, including climate change (−9.9% and −12.1%, respectively), but increased metal use (+29.5% and +13.0%, respectively). A hotspot analysis identifies research opportunities for reducing environmental impacts such as material innovation through substituting silver (metallization) and ethylene vinyl acetate (encapsulant), or, more broadly, improving process efficiency and integrating more renewables into the electricity mix. The environmental impact is further evaluated to consider technological developments and evolving electricity mixes to the year 2034, showing the impacts of SHJ and TOPCon are reduced by >10% for all six identified high-value impact categories. These are then used to model European PV deployment between 2023 and 2034, considering various manufacturing scenarios, which show that this could result in climate change emissions of 2 eq., though implementation of the Net-Zero Industry Act could reduce this to 0.31 Gt CO ₂ eq. Finally, sensitivity analysis is conducted to investigate uncertainty associated with modeling future impacts, comparing the 2024 and 2025 International Technology Roadmap for Photovoltaics. The sensitivity analysis results provide additional confidence in the findings of the initial comparison and support the conclusion that SHJ technology has, and will continue to have, the lowest environmental impact of the three investigated technologies.