Photodetection in single-crystal 3D MAPbI3 and quasi-2D (PEA)2(MA)Pb2I7 perovskites

Hybrid organic-inorganic perovskites are emerging as key materials for next-generation photodetectors, where the compositional and structural tunability and exceptional optoelectronic properties provide a powerful strategy to tune the microscopic mechanisms governing the photoresponse. Here, 3D MAPbI3 and quasi-2D (PEA)(2)(MA)Pb2I7 single-crystal photodetectors are comparatively investigated under dark and illuminated conditions. The devices employ two lateral Ag-paste contacts and therefore operate as photoconductors, in which illumination increases the crystal conductivity through the generation of mobile charge carriers under an applied bias. Both devices exhibit a nearly ohmic behavior in the dark and under illumination. The photocurrent increases almost linearly with the incident optical power, with a power-law exponentia of alpha approximate to 0.9 for both crystals. The 3D perovskite shows higher conductivity, with a dark current of 10(-10 )A at V-bias = 1 V, whereas the quasi-2D device exhibits a strongly suppressed dark current of 10(-12 )A under the same bias condition. Prompt and reversible photocurrent switching is observed in both devices within the temporal resolution of the experimental setup; however, the 3D crystal also displays an additional slow current rise, suggesting the activation of a secondary light-induced process. Spectral measurements further reveal a widened bandgap in the quasi-2D perovskite, consistent with its layered structure. Overall, this comparative study highlights the key role of dimensionality and organic-cation engineering in balancing efficient photogeneration, dark-current suppression, and low-noise photodetection.