Prof Yen-Hung Lin

Abstract:

The commercialization of perovskite solar cells is bottlenecked by inefficient, trial-and-error approaches reliant on human expertise in both material discovery and device fabrication (1-3). Here, we introduce an autonomous closed-loop framework that integrates machine learning (ML)-driven material discovery with an automated manufacturing platform. The system employs active learning and quantum modeling to rapidly identify high-performance molecules, while the platform uses Bayesian optimization and symbolic regression in a feedback loop to continuously refine the fabrication process. This integrated approach enabled the discovery of a passivation molecule, 5-(aminomethyl)nicotinonitrile hydroiodide (5ANI), which yielded 0.05 cm² solar cells with a power conversion efficiency (PCE) of 27.22% (certified maximum power point tracking (MPPT) efficiency of 27.18%) and 21.4 cm² mini-modules with a PCE of 23.49%. Moreover, the devices exhibited long-term operational stability, retaining 98.7% of their initial efficiency after 1,200 hours of continuous operation under the ISOS-L-1I protocol. Crucially, the automated platform achieved an efficiency reproducibility nearly 5 times that of manual fabrication. This work establishes an automated closed-loop system that synergizes ML-powered discovery with the high-fidelity data from automated manufacturing, setting a benchmark for autonomous discovery and manufacturing in photovoltaics and materials.

Abstract:

All-inorganic perovskite solar cells (PSCs) have emerged as a prominent research focus because the high thermal/photo stability they can offer is critical to commercialization of the burgeoning photovoltaic (PV) technology. However, there remain issues pertaining to the susceptibility of the all-inorganic perovskites to surface degradation from moisture ingress under ambient conditions and the suboptimal PV efficiency that still lags substantially behind that of their organic-inorganic hybrid counterparts. To address these challenges, this work employs an in situ self-assembly strategy to construct a 1D/3D perovskite heterojunction on top of the all-inorganic perovskite using tetrabutylammonium trifluoromethanesulfonate (TTFS). While typical ammonium salts only provide a cationic barrier or weak passivation, the TTFS-based design uniquely synergizes a hydrophobic cationic barrier with strong anionic passivation, and concurrently creates fast electron extraction channels through a nanostructured interface. This approach overcomes the conventional trade-off between stability and efficiency. By exploiting it to optimize a semi-transparent wide-band PSC for 4-terminal (4-T) tandem devices, a certified power conversion efficiency (PCE) of 17.10% was achieved together with exceptional operational stability under maximum power point (MPP) tracking-maintaining 80% of the initial PCE (T₈₀) after operating for 1210 hours at 65 °C and 650 hours at 85 °C (ISOS-L-2). When it is combined with a narrow-band all-inorganic PSC in the 4-T tandem configuration, a certified efficiency of 21.54% was obtained, which is the highest reported for this type of tandem cells. Through synergistic optimization of interface stabilization and tandem optoelectronic management, this work provides valuable insights for developing efficient and stable all-inorganic perovskite tandem solar cells.

Abstract:

Vacuum-based deposition is a scalable, solvent-free industrial method ideal for uniform coatings on complex substrates. However, all vacuum-deposited perovskite solar cells fabricated by thermal evaporation trail solution-processed counterparts in efficiency and stability due to film quality challenges, necessitating advancement and improved understanding. Here, we report a co-evaporation route for 1.67-eV wide-bandgap perovskites by introducing a PbCl2 co-source to optimize film quality. We promote perovskite formation with pronounced (100) “face-up” orientation and deliver a certified all vacuum-deposited solar cell with 18.35% efficiency (19.3% in the lab) for 0.25-cm2 devices (18.5% for 1-cm2 cells). These cells retain 80% of peak efficiency after 1,080 hours under the ISOS-L-2 protocol. Leveraging operando hyperspectral imaging, we provide spatiotemporal spectral insight into halide segregation and trap-mediated recombination, correlating microscopic luminescence features with macroscopic device performance while distinguishing radiative from non-ideal recombination channels. We further demonstrate 27.2%-efficient 1-cm2 evaporated perovskite-on-silicon tandems and outdoor stability of all vacuum-deposited tandems in Italy, retaining ~80% initial performance after 8 months.

Abstract:

Multivalent, resonance-stabilized amidinium ligands enable stronger chemical coordination and reduced deprotonation compared with conventional monovalent ammonium ligands in low-dimensional perovskites. Here, we introduce a controllable one- to two-dimensional (1D-to-2D) structural transition strategy by systematically tuning ligand conformation, thereby modulating hydrogen bonding, π-π stacking, and basicity to elucidate the relationship between molecular structure, interfacial interactions, and resulting dimensionality. The 1D-amidinium perovskite structure, with its pronounced geometric anisotropy, impedes uniform surface coverage and defect passivation. In contrast, the 2D-amidinium perovskite forms a continuous, homogeneous interfacial layer, enabling more effective defect passivation and favorable energy-level alignment. With dimensionality control, inverted 3D/2D-amidinium perovskite solar cells deliver 25.4% power conversion efficiency (1.1 square centimeters, steady-state certified) and maintain >95% of their initial efficiency after 1100 hours of continuous 1-sun operation at 85°C.

Abstract:

Perovskite solar cells (PSCs) are emerging as a particularly promising technology to enhance the world’s renewable energy generation capacity. As PSCs are transitioning from research to industrial-scale production, there is an important opportunity to establish sustainable manufacturing pathways. Here, we present a closed-loop framework for the development of environmentally sustainable PSCs and highlight strategies to achieve this vision. First, we analyse the sourcing of raw materials and compare two established PSC fabrication techniques, vapour-phase deposition and solution processing, evaluating their respective advantages and limitations in terms of economic feasibility and environmental impact. Second, we examine solution processing methods, focusing on solvent system design for the preparation of high-quality perovskite films and on the use of non-hazardous or less-hazardous solvents. Third, we examine potential lead-release concerns during PSC operation and discuss approaches to minimize associated environmental risks. Fourth, we summarize effective recycling methods for main PSC components to support a circular production model. Finally, we identify key challenges and outline future research directions to achieve fully sustainable, closed-loop PSC technologies.