Deep Green

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    Co‐doping approach for enhanced electron extraction to TiO2 for stable inorganic perovskite solar cells
    (2025) Gries, Thomas W.; Regaldo, Davide; Köbler, Hans; Putri Hartono, Noor Titan; Harvey, Steven P.; Simmonds, Maxim; Frasca, Chiara; Härtel, Marlene; Sannino, Gennaro V.; Félix, Roberto; Hüsam, Elif; Saleh, Ahmed; Wilks, Regan G.; Zu, Fengshuo; Gutierrez‐Partida, Emilio; Iqbal, Zafar; Loghman Nia, Zahra; Yang, Fengjiu; Delli Veneri, Paola; Zhu, Kai; Stolterfoht, Martin; Bär, Marcus; Weber, Stefan A.; Schulz, Philip; Puel, Jean‐Baptiste; Kleider, Jean‐Paul; Unger, Eva; Wang, Qiong; Musiienko, Artem; Abate, Antonio
    Inorganic perovskite CsPbI3 solar cells hold great potential for improving the operational stability of perovskite photovoltaics. However, electron extraction is limited by the low conductivity of TiO2, representing a bottleneck for achieving stable performance. In this study, a co‐doping strategy for TiO2 using Nb(V) and Sn(IV), which reduces the material's work function by 80 meV compared to Nb(V) mono‐doped TiO2, is introduced. To gain fundamental understanding of the processes at the interfaces between the perovskite and charge‐selective layer, transient surface photovoltage measurements are applied, revealing the beneficial effect of the energetic and structural modification on electron extraction across the CsPbI3/TiO2 interface. Using 2D drift‐diffusion simulations, it is found that co‐doping reduces the interface hole recombination velocity by two orders of magnitude, increasing the concentration of extracted electrons by 20%. When integrated into n-i-p solar cells, co‐doped TiO2 enhances the projected TS80 lifetimes under continuous AM1.5G illumination by a factor of 25 compared to mono‐doped TiO2. This study provides fundamental insights into interfacial charge extraction and its correlation with operational stability of perovskite solar cells, offering potential applications for other charge‐selective contacts.
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    Direct air capture via counter‐current NaOH absorption system : evolution of pH for subsequent plasma‐enhanced CO₂ utilization
    (2025) Seithümmer, Valentin Benedikt; Dubiel, Christoph; Kaufmann, Samuel Jaro; Chinnaraj, Haripriya; Rößner, Paul; Birke, Kai Peter
    Direct air capture (DAC) technologies offer a promising approach to mitigate anthropogenic climate change by enabling net negative emissions. CO2 absorption using NaOH represents an efficient solution within the proposed BlueFire carbon cycle, which integrates DAC with plasma technology for syngas production. Optimizing a DAC plant control relies on understanding the pH profile as a key parameter. A bubble column absorption model with pure CO2 was experimentally adapted for a counter‐current flow setup with ambient air, reproducing a staged pH decrease. An optimal absorption endpoint was determined by identifying the maximum slope of the pH decline, indicating high reaction progress. X‐ray diffraction analysis of the absorption products validated the theoretical model of carbonate formation.