CsPbI₃, an inorganic perovskite with an excellent bandgap and thermal stability, exhibits great potential for Si-perovskite tandem solar cells although it is highly sensitive to moisture. Here we address this by fabricating CsPbI₃ solar cells under high humidity, controlling annealing via the humidity-dependent volatilization of dimethylammonium iodide. Surface passivation with 1,8-diaminooctane (DAO) reduces Pb surface defects, which enhances charge transport and forms a hydrophobic, moisture-resistant film. The DAO-passivated CsPbI₃ solar cell achieves a power conversion efficiency of 17.7% and retains 92.3% of its initial efficiency after 1500 minutes of maximum power point tracking in 30% relative humidity without encapsulation, demonstrating improved humidity stability. All solution-processed layers were fabricated in ambient air, highlighting their potential for cost-effective mass production.

As we move towards the commercialization and upscaling of perovskite solar cells, it is essential to fabricate them in ambient environment rather than in the conventional glove box environment. The efficiency of ambient-processed perovskite solar cells lags behind those fabricated in controlled environments, primarily owing to external environmental factors such as humidity and temperature. In the case of device fabrication in ambient environments, relying solely on a single parameter, such as temperature or humidity, is insufficient for accurately characterizing environmental conditions. Therefore, the dew point is introduced as a parameter which accounts for both temperature and humidity. In this study, a machine learning model was developed to predict the efficiency of ambient-processed perovskite solar cells based on meteorological data, particularly the dew point. A total of 238 perovskite solar cells were fabricated, and their photovoltaic parameters and dew points were collected from March to December 2023. The collected data were used to train various tree-based machine learning models, with the random forest model achieving the highest accuracy. The efficiencies of the perovskite solar cells fabricated in January and February 2024 were predicted with a MAPE of 4.44%. An additional Shapley Additive exPlanations analysis confirmed the significance of the dew point in the performance of perovskite solar cells.

Monolithic perovskite–silicon tandem solar cells with MoO_x hole selective contact silicon bottom solar cells show a power conversion efficiency of 8%. A thin 15 nm-thick MoO_x contact to n-type Si was used instead of a standard p⁺ emitter to collect holes and the SiO_x/n⁺ poly-Si structure was deposited on the other side of the device for direct tunneling of electrons and this silicon bottom cell structure shows ~15% of power conversion efficiency. With this bottom carrier selective silicon cell, tin oxide, and subsequent perovskite structure were deposited to fabricate monolithic tandem solar cells. Monolithic tandem structure without ITO interlayer was also compared to confirm the role of MoO_x in tandem cells and this tandem structure shows the power conversion efficiency of 3.3%. This research has confirmed that the MoO_x layer simultaneously acts as a passivation layer and a hole collecting layer in this tandem structure.

This study proposes a titanium silicide (TiSi2) recombination layer for perovskite/tunnel oxide passivated contact (TOPCon) 2-T tandem solar cells as an alternative to conventional transparent conductive oxide (TCO)-based recombination layers. TiSi2 was formed while TiO2 was made by oxidizing a Ti film deposited on the p(+)-Si layer. The reaction formation mechanism was proposed based on the diffusion theory supported by experimental results. The optical and electrical properties of the TiSi2 layer were optimized by controlling the initial Ti thicknesses (5-100 nm). With the initial Ti of 50 nm, the lowest reflectance and highly ohmic contact between the TiO2 and p(+)-Si layers with a contact resistivity of 161.48 m Omegacm(2) were obtained. In contrast, the TCO interlayer shows Schottky behavior with much higher contact resistivities. As the recombination layer of TiSi2 and the electron transport layer of TiO2 are formed simultaneously, the process steps become simpler. Finally, the MAPbI(3)/TOPCon tandem device yielded an efficiency of 16.23%, marking the first reported efficiency for a device including a silicide-based interlayer.

In this work, nickel silicide was applied to tandem solar cells as an interlayer. By the process of thermal evaporation, a layer of NiO_x, hole transport layer (HTL) was deposited on n⁺ poly-Si layer directly. Nickel silicide was simultaneously formed by nickel diffusion from NiO_x to n⁺ poly-Si layer during the deposition and annealing process. The I–V characteristics of NiO_x/n⁺ poly-Si contact with nickel silicide showed ohmic contact and low contact resistivity. This structure is expected to be more advantageous for electrical connection between perovskite top cell and TOPCon bottom cell compared to the NiO_x/TCO/n⁺ poly-Si structure showing Schottky contact. Furthermore, nickel silicide and Ni-deficient NiO_x thin film formed by diffusion of nickel can improve the fill factor of the two sub cells. These results imply the potential of a NiO_x/nickel silicide/n⁺ poly-Si structure as a perovskite/silicon tandem solar cell interlayer.