Remarkable Enhancement of Detectivity and Stability in Flexible n–i–p-Type Perovskite Photodetectors by Concurrent Use of Various Two-Dimensional Materials: Doped Graphene, Graphene Quantum Dots, WS₂, and h-BN

Flexible perovskite photodetectors (PDs) are highly attractive as a promising candidate for one of the key components in next-generation optoelectronic systems, but the conventional transport materials are brittle and vulnerable to environmental ambient conditions, degrading long-term and mechanical stabilities. Here, we concurrently employ various two-dimensional (2D) materials such as doped graphene (GR), graphene quantum dots (GQDs), WS 2, and h-BN for flexible perovskite PDs, thereby particularly enhancing their detectivity and stability. The doping of the GR electrode reduces the sheet resistance almost without degrading the transmittance, and the addition of GQDs in the active layer increases the size of the crystals and their crystallinity, enhancing the long-term stability. The WS 2 acts as an electron transport layer as well as an optically sensitive layer. The h-BN makes it more difficult for carriers to overcome the barrier at the interface due to the increased height, thereby sharply reducing the DC even at zero bias, resulting in a remarkable increase of the detectivity. The mechanical stability of the PDs is also greatly improved by incorporating the flexible 2D constituent materials.