Additive‐Engineered Dion‐Jacobson Perovskites (4AMP)(FA)Pb ₂ I ₇ for Self‐Powered Efficient Photodetectors

Dion-Jacobson (DJ) perovskites are being explored for optoelectronics, owing to their improved structural merit over Ruddlesden-Popper (RP) perovskites. However, DJ perovskites have various inherent issues, such as poor film morphology, relatively inferior charge transport properties, which result in less efficient devices. Recently, additive engineering has been used to control crystallization, reduce defects in bulk and RP perovskites, while these efforts are also needed for DJ perovskites. This work demonstrates the additive engineering of quasi-2D (4AMP)(FA)Pb₂I₇ DJ perovskites (4AMP: 4-(aminomethyl) piperidinium, FA: formamidinium) using MoS₂ nanoflakes, which offer smooth and dangling bond-free surfaces, thus could promote the epitaxial growth of perovskite crystallites. The effect of MoS₂ nanoflakes addition on the structural, chemical, optical, morphological, and optoelectronic properties of DJ perovskites are studied. Photodetectors fabricated using additive-engineered DJ perovskites with optimized MoS₂ nanoflakes concentration has shown R ∼52.28 mA/W, D ∼2.4 × 10¹⁰ Jones, EQE ∼13.79%, which are the highest among self-powered 2D MHPs thin film-based charge transport layer-free photodetectors reported. This performance is attributed to enhanced crystallographic orientation in the vertical direction, reduced strain, compact film morphology, formation of charge transfer network, and reduced work function of engineered DJ perovskites, which demonstrate the potential of combining quasi-2D perovskites and transition-metal dichalcogenide TMD(transition-metal dichalcogenide) materials to develop efficient optoelectronic devices.