Development of 2D organic-inorganic hybrid perovskite/transition metal dichalcogenide heterostructured optical absorption layers

Developing high-performance photodetectors with a p-n diode structure involves selecting suitable semiconductor materials as absorption layers and enhancing their properties, which is a key focus area. Particularly in recent years, two-dimensional (2D) organic-inorganic hybrid perovskites (OHPs) and transition metal dichalcogenides (TMDs) have gained great attention for use in diode structures due to their superior optical and electronic properties. Although some studies in the literature have attempted to reveal the underlying photophysical processes in various p-n OHP/TMD heterostructures, there are still inconsistencies and processes that have not been explained yet in detail. Within the scope of this thesis, BA2MAPb2I7/MoS2, BA2PbBr4/MoS2 and BA2PbI4/MoS2 heterostructures were produced for the first time, and systematic measurements were carried out to investigate the photophysical processes. Bulk 2D RP OHP and monolayer MoS2 single crystals were first synthesized using solution-based crystal growth and chemical vapor deposition (CVD) techniques, respectively. Studies were also carried out on the synthesis of a monolayer MoS2 film with a large surface area of the order of millimeters using the glass-assisted CVD approach. 2D RP OHP single crystals with low thicknesses on the order of tens of nanometers were produced on SiO2/Si surfaces via mechanical exfoliation. The OHP/MoS2 heterostructures were formed by transferring low-thickness perovskite single crystals onto monolayer MoS2 using the polymer-based PPC/PDMS stamping method. The PL intensity of perovskite within the junction region of the produced BA2MAPb2I7/MoS2 heterostructures is notably lower, by several times, compared to outside the junction. Furthermore, it has been observed that the PL intensity of MoS2 within the junction region of the produced BA2PbBr4/MoS2 and BA2PbI4/MoS2 heterostructures is significantly lower compared to outside the junction. These observations lead to the conclusion that the produced heterostructures exhibit characteristics of a type-II heterojunction configuration. In the BA2MAPb2I7/MoS2 heterostructures, the PL intensity of the perovskite layer diminishes notably due to the quenching effect resulting from charge transfer. Particularly within the heterostructure region, the redshift of the PL peak from a 678 nm wavelength to 682 nm indicates the prevalence of negative trions in the MoS2 emission spectrum, providing evidence of charge transfer within the heterostructure. Additionally, the variation in photophysical processes based on the thickness of the perovskite layer was investigated. It was observed that as the thickness decreases below 10 nm, the PL quenching effect increases significantly, nearly extinguishing the entire PL spectrum of the perovskite layer. This is attributed to the weakening of the charge transfer process with increasing thickness, due to the photon recycling effect. On the contrary, in some heterostructures, a significant increase in PL intensity, up to 8 times, was observed. This increase is speculated to be due to energy transfer. Furthermore, the presence of the interlayer exciton (IX) emission spectrum in the BA2PbBr4/MoS2 and BA2PbI4/MoS2 heterostructures was investigated and was not observed within the 532-1950 nm wavelength range. Moreover, akin to BA2MAPb2I7/MoS2 heterostructures, a notable increase, up to 12 times, in the PL quenching in the MoS2 emission spectrum was observed with decreasing thickness of the perovskite layer in BA2PbBr4/MoS2 and BA2PbI4/MoS2 heterostructures.