Thomas Feeney

This study employs in situ probing to control the crystallization dynamics of Sn–Pb mixed perovskites during vacuum-assisted growth and annealing, enabling scalable fabrication of high-quality perovskite films and all-perovskite tandem photovoltaics.

Vapor phase deposition processes for the fabrication of perovskite solar cells show great potential for transferring from laboratory‐scale to continuous industrial‐scale production. Precise process control and high process reproducibility are of utmost importance to unlock their full potential. In this regard, the sublimation behavior and rate control of organic precursor materials in thermal evaporation processes are particularly challenging. Here, it is investigated in detail how the particle size of formamidinium iodide (FAI) and the crucible geometry influence the directionality of the emitted vapor flux. It is shown that conical crucibles lead to beam focusing of the vapor flux, while cylindrical crucibles show a broader, less directional emission profile. This leads to differences in the homogeneity of material deposition depending on the lateral source‐to‐substrate distance. Furthermore, there is a substantial impact of FAI particle size on the directionality of the vapor flux for conical crucibles, affecting the deposited material thickness gradient over the substrate. Analyzing commonly employed inorganic materials reveals the strong material dependence of effusion characteristics, leading to additional complexity for multi‐material deposition processes. The findings emphasize that both homogenization of organic precursor materials and optimization of source geometry and arrangement are critical for achieving uniform deposition and, consequently, improved process reproducibility.

Vapor phase deposition methods are readily able to achieve uniform coverage of large‐area substrates and are widely considered promising for industrial‐scale perovskite solar cell fabrication. However, as perovskite‐silicon tandem solar cells approach commercialization, practical considerations of manufacturing throughput come into play. Here, it is shown that the inherent sublimation characteristics of the organic precursor formamidinium iodide (FAI) make increasing the deposition rate of FA‐based co‐evaporated perovskites negatively impact replicability and lead to a substantial decrease in power conversion efficiency (PCE). These losses are linked to reduced film homogeneity and the emergence of carbon‐rich regions within the perovskite layer. To mitigate these rate‐induced effects, two approaches are explored: source layout optimization and material preconditioning. Utilizing dual FAI sources rather than a single FAI source reduces the relative PCE drop from ≈23% _rel to ≈9% _rel at a deposition rate of ≈18 nm min ⁻¹ (14.8% PCE @ maximum power point (MPP)) compared to the baseline rate of 5 nm min ⁻¹ (16.2% PCE @MPP). Alternatively, preconditioning a single FAI source reduces the performance losses from ≈31% _rel to ≈26% _rel at a deposition rate of ≈21 nm min ⁻¹ . These findings underscore the importance of tailored source strategies to enable high‐rate FA‐based co‐evaporated perovskites without compromising device performance.

Vapor phase deposition processes hold great potential for industrializing the deposition of perovskite-based absorbers, offering a pathway to commercialization.

Integrating wide-bandgap organic-inorganic lead halide perovskite absorber layers with Si bottom solar cells into tandem architectures offers significant potential for increasing power conversion efficiency (PCE). However, achieving high-performance monolithic tandem devices remains challenging, particularly when processing perovskite top cells on top of industrial silicon bottom cells, featuring polycrystalline silicon on oxide (POLO) passivating contacts, as implemented in “TOPCon” solar cells. Here, we employ an advanced silicon bottom cell architecture incorporating full-area electron-selective POLO front contacts and laser-structured hole-selective POLO back contacts. We perform the N₂ annealing at an elevated temperature of silicon bottom cells, effectively curing sputter-induced damage in the full-area electron-selective POLO contact of the recombination junction and enhancing the interface between transparent conductive oxide and the n-type doped poly-Si layer. Additionally, this annealing treatment likely improves the rear small-area contact between the aluminum and the p+ poly-Si. Furthermore, we investigate how the nickel oxide layer regulates the substrate morphology and affects the charge carrier mechanisms for the top perovskite solar cells. These strategies remarkably promote charge carrier management, achieving a monolithic perovskite/POLO-Si tandem solar cell with a PCE of 31%. Moreover, the unencapsulated tandem cell retained 93% of its initial efficiency after operating for 240 hours at maximum power point under one sun intensity, 25°C, and 30% relative humidity (ISOS-L-1), the extrapolated T80 lifetime is estimated to be 740 hours.

Monolithic all-perovskite tandem photovoltaics promise to combine low-cost and high-efficiency solar energy harvesting with the advantages of all-thin-film technologies. To date, laboratory-scale all-perovskite tandem solar cells have only been fabricated using non-scalable fabrication techniques. In response, this work reports on laser-scribed all-perovskite tandem modules processed exclusively with scalable fabrication methods (blade coating and vacuum deposition), demonstrating power conversion efficiencies up to 19.1% (aperture area, 12.25 cm²; geometric fill factor, 94.7%) and stable power output. Compared to the performance of our spin-coated reference tandem solar cells (efficiency, 23.5%; area, 0.1 cm²), our prototypes demonstrate substantial advances in the technological readiness of all-perovskite tandem photovoltaics. By means of electroluminescence imaging and laser-beam-induced current mapping, we demonstrate the homogeneous current collection in both subcells over the entire module area, which explains low losses (rel) in open-circuit voltage and fill factor for our scalable modules.