The efficiency and longevity of perovskite solar cells (PSCs) are heavily influenced by the interfaces between different layers within the device. Effective interface engineering is paramount to minimize charge recombination losses and facilitate efficient charge extraction. In this critical aspect, 1,4-Phenylenediamine Dihydriodide (PDAI) has emerged as a powerful additive, enabling significant advancements in PSC performance through targeted interface modification.

PDAI's primary role in interface engineering involves its ability to promote the formation of a 2D perovskite layer at the boundary between the 3D perovskite absorber and the hole transport layer (HTL). This 2D/3D heterostructure is key to unlocking enhanced device characteristics. When PDAI is applied as a post-treatment or incorporated into the fabrication process, it influences the morphology of the perovskite film, leading to several beneficial outcomes.

Scientific investigations have demonstrated that PDAI treatment results in larger crystallite sizes and a reduction in grain boundaries within the perovskite film. Grain boundaries are often sites for charge recombination and defect accumulation. By creating a more compact and defect-free film, PDAI minimizes these detrimental pathways. This improved film quality directly leads to a lower trap density and more efficient transport of charge carriers (electrons and holes) to their respective electrodes.

Furthermore, the introduction of the 2D perovskite layer formed by PDAI can optimize the energy level alignment between the perovskite absorber and the HTL. This alignment is crucial for efficient charge transfer, ensuring that holes generated in the perovskite layer are readily passed to the HTL with minimal energy loss. The enhanced interaction and better physical contact between the layers, facilitated by PDAI, contribute to higher open-circuit voltages (Voc) and fill factors (FF), both of which are critical parameters for overall PCE.

The precise control over PDAI concentration is vital for achieving these interface engineering benefits. Studies indicate an optimal range where PDAI maximally enhances grain growth and passivates defects without introducing excessive material that could hinder performance. The successful implementation of PDAI in optimizing the perovskite/HTL interface not only boosts the initial efficiency of PSCs but also contributes to their overall stability and longevity. This approach is a testament to how targeted chemical modifications at the molecular level can dramatically improve the performance of advanced photovoltaic devices.