Rutger Schlatmann

Carborane-based electron transport material enables high-efficiency, fullerene-free monolithic perovskite/silicon tandem solar cell.

Magnetron sputtering process for ultra-low loading catalyst development and integration into AEM electrolyser.

The upscaling of perovskite/silicon tandem solar cells is an increasingly important topic in research to bridge the gap between laboratory scale performance and industrial application. This requires adapting well-established technologies to enable the processing of upscaled tandem cell manufacturing steps, including the transparent conductive oxide (TCO) front electrode by magnetron sputtering and the metal contact by screen printing. For state-of-the-art silicon heterojunction (SHJ) solar cells, both the TCO and the metal contact are annealed at temperatures around 200 °C. Perovskite films in contrast are known to degrade at such high temperatures, which makes the processing of the front contact for perovskite based solar cells more challenging. In this work, we demonstrate an optimized screen-printing process that, with the right choice of sputtering process parameters, enables a low TCO/Ag contact resistivity of around 1 mΩcm² at a maximum processing temperature of 135 °C and therefore suitable for (most) perovskite absorbers. The interaction between the TCO and the silver paste is analyzed in detail with respect to achieving low contact resistivity between the two layers. Our results demonstrate that controlling the hydrogen content during the sputtering process is critical: higher hydrogen levels result in a clear increase in the specific contact resistivity. Finally, we show a screen-printed tandem device that further confirms the process feasibility.

Surface defects of low-temperature sputtered NiO _x migrate into the perovskite bulk and are detrimental to the NiO _x –perovskite interface and the cell stability. Bulk doping with copper and/or SAM surface passivation of the NiO _x improve the stability.

Direct ammonia fuel cells (DAFCs) hold great promise as clean energy conversion devices due to their carbon-free exhaust, the high energy density and liquid-phase storability of ammonia, and use of an existing production and distribution infrastructure. When using the state-of-the-art anion exchange membranes, ammonia crossover from the cathode to the anode, can cause rapid decay in DAFC performance as the current density increases. Mixed metal oxides containing manganese-nickel-cobalt have emerged as NH₃ tolerant cathode catalysts but their systematic testing under variable loading conditions in DAFC is rarely reported. Here, we examine low-temperature DAFCs with electrodeposited platinum (Pt), manganese-cobalt (MnCo), and manganese-nickel-cobalt (MnNiCo) cathodes on Ni foam. To isolate cathodic effects, all cells use identical Pt on Ni Foam anodes with alkaline ammonia feeds. Structural characterization confirms defect-rich spinel coatings. MnCo achieves oxygen reduction reaction (ORR) performance comparable to Pt, sustaining higher load voltage with lower interfacial resistance and larger capacitance, while MnNiCo shows restricted performance and rapid voltage loss, indicating sluggish charge transfer and fewer active sites. These results identify electrodeposited MnCo on Ni foam as a promising, scalable PGM-free cathode for DAFCs and highlight compositional and mesostructural tuning as key levers to improve catalytic activity and device performance.

The first comprehensive electrochemical test protocol for probing both steady-state and transient operations of low temperature direct ammonia fuel cells (DAFCs) is introduced. It combines galvanostatic holds, cyclic staircase loads mimicking start-up/shut-down, long dynamic current loading representative of automotive application, and extended open-circuit periods. A hydrogen reference electrode at the anode inlet enables three-electrode operation, so anode and cathode overpotentials, impedance spectra, and polarization curves can be recorded simultaneously and de-convoluted in real time. DAFCs (25 cm²) with ultralow catalyst loading (0.3 mgPt/cm²) electrodeposited on nickel foam were operated on 1.0 M NH₃ + 1.0 M KOH at 60 °C. Durability measurements indicate that voltage decay is dominated by reversible anode deactivation driven by fuel depletion; full recovery upon fuel replacement confirms minimal permanent catalyst damage. Impedance analysis indicates that the cathodic double-layer capacitance increases, consistent with flooding. Mass spectrometry identifies N2 as the sole gaseous product at 0.2 V with no detectable NOx. The protocol’s ability to identify these phenomena over a single campaign provides an essential tool for future DAFC development. Together, the results establish links between operating regime, fuel utilization, and degradation pathway. They furnish a benchmark for emerging membranes, catalysts, and cell architectures to be compared.

Through chemical sensitization imparted by conformal atomic layer deposition of NiO, on-chip fabricated NiO-modified mesoporous NbTiO _x thin films achieve a 13-fold enhancement in chemoresistive response toward acetone compared to pristine NbTiO _x .