Opportunity
Metal halide perovskite solar cells (PSCs), particularly in tandem configurations like perovskite-organic tandem solar cells (PO-TSCs), are promising for high power conversion efficiency (PCE). However, a major obstacle to their commercialization and long-term stability is the severe halide phase segregation that occurs during device operation, primarily driven by halide migration through vacancies. This segregation, especially in mixed iodide/bromide perovskites, leads to efficiency degradation. Concurrently, under continuous illumination or heating, lead ions (Pb²⁺) in the perovskite are prone to reduction to metallic lead (Pb⁰), which further deteriorates device performance and stability. Existing strategies to suppress halide segregation, such as crystallization control or defect passivation, often fail to simultaneously address the facile reduction of Pb²⁺ to Pb⁰. Moreover, many additives used are either inorganic compounds with limited synthetic tunability or sacrificial agents that deplete quickly. Therefore, there is a critical need for a sustainable, multifunctional additive that can concurrently eliminate both halide segregation and metallic lead formation without introducing new defects.
Technology
The patent addresses these challenges by inventing a novel perovskite layer comprising a mixture of a halide perovskite and a specific sulfonyl naphthoquinone-based compound. The core innovation is the use of this compound, particularly derivatives like anthraquinone-2-sulfonate (AQS) with hydrogen (AQSH), ammonium (AQSN), or phenethylammonium (AQSP) cations, as a redox mediator. This mediator is strategically incorporated at the grain boundaries of the perovskite crystal structure. Its function is to enable sustainable and selective electron shuttling: it oxidizes detrimental metallic Pb⁰ back to Pb²⁺ while simultaneously reducing iodine species (I⁰/I₂) back to iodide (I⁻). This dual-action mechanism directly counteracts the two primary degradation pathways. The AQS core provides the essential redox activity, with a tailored potential suitable for interacting with both Pb and I species. Furthermore, the cationic substitutions (e.g., NH₄⁺, PEA⁺) enhance the molecule's binding to the perovskite surface, providing additional defect passivation at grain boundaries and improving interfacial stability. The perovskite layer is fabricated by adding a small amount (0.3-1 mol%) of the redox mediator to the perovskite precursor solution, followed by spin-coating and annealing. This integration effectively suppresses halide segregation and mitigates lead reduction in a sustained, non-sacrificial manner.
Advantages
- Simultaneously suppresses halide phase segregation and metallic lead (Pb⁰) formation through a sustainable redox shuttle mechanism.
- Enhances the long-term operational stability of perovskite solar cells.
- The sulfonyl naphthoquinone-based additives are synthetically tunable, allowing for optimization of redox potential and passivation properties.
- Functions in a sustained, non-sacrificial manner, unlike transient additives.
- Reduces trap density in the perovskite film, leading to improved charge carrier lifetime.
- Enables high open-circuit voltage (V_oc), achieving a low V_oc deficit for wide-bandgap perovskites (~1.8 eV).
Applications
- As the active layer in high-efficiency, stable single-junction perovskite solar cells (PSCs).
- As the wide-bandgap subcell in high-performance monolithic perovskite-organic tandem solar cells (PO-TSCs).
- As a key component in other multi-junction or tandem solar cell architectures (e.g., perovskite-silicon).
- Potentially applicable in other perovskite-based optoelectronic devices where halide segregation and ion migration are concerns, such as LEDs or photodetectors.
