Negative Photoconductivity in Tin-Based Organic-Inorganic Hybrid Perovskites

Organic-inorganic hybrid perovskites (OIHPs) have emerged as next-generation materials for optoelectronic applications due to their superior photophysical properties and chemical diversity. In this work, we synthesized a new series of OIHPs single crystals with the general formula (R/S-MBA)SnX₃ (X = I, Br, and Cl, MBA = methylbenzylamine) and explore their unique photophysical properties. Single crystal X-ray diffraction analysis confirms that (R/S-MBA)SnX₃ crystals are in P2₁2₁2₁ space group and highly distorted [SnX₆] octahedra are arranged in 1D 2-fold zigzag structure. Negative photoconductivity (NPC), in which current density decreases under light illumination, is identified through photoconductivity measurements in humid air. Furthermore, an increase in dark current by a factor of 10³ was observed with the rise in relative humidity from 25% to 50%. We argue that the surface moisture adsorption and photo-desorption contributes to NPC effect. This mechanism is consistent with the observation of photoconductivity transition from negative to positive when the environment condition changes from air to Ar. We expect this NPC phenomenon induced by external environmental factors can be applied to novel optoelectronic applications.
Acknowledgement
This research was supported by the Digital Research Innovation Institution Program Through the National Research Foundation of Korea (NRF) funded by Ministry of Science and ICT (RS-2023-00283597).