An intrinsic electrical conductivity study of perovskite powders MAPbX₃ (X = I, Br, Cl) to investigate its effect on their photovoltaic performance

An investigation into the intrinsic electrical conductivity of perovskite powders MAPbX(3), where X represents iodine (I), bromine (Br), or chlorine (Cl), was conducted to explore its impact on their photovoltaic performance. Results revealed that MAPbCl(3) demonstrated light absorption ability in the ultraviolet and visible regions, while MAPbBr(3) showed capacity for light absorption at longer wavelengths in the visible spectrum. On the other hand, MAPbI(3) exhibited good absorption at longer wavelengths, indicating its ability to absorb light in the near-infrared region. The optical bandgap of each perovskite was determined to be 2.90 eV for MAPbCl(3), 2.20 eV for MAPbBr(3), and 1.47 eV for MAPbI(3). The electrical conductivities of these powders were measured in-plane using the four-probe method and through-plane by electrochemical impedance spectroscopy (EIS). Electrochemical impedance spectroscopy (EIS) studies revealed a significant change in the conductivity of the MAPbI(3) perovskite at temperatures between 80 degrees C and 100 degrees C. This change could be attributed to structural modifications induced when the temperature exceeds these values. The through-plane conductivity changed from 3 x 10(-8) S cm(-1) at 60 degrees C to approximately 6 x 10(-5) S cm(-1) at 120 degrees C and around 2 x 10(-3) S cm(-1) at 200 degrees C. Meanwhile, the sheet conductivity (in-plane conductivity) measurements performed at ambient temperature reveal that sheet conductivities are 489 x 10(3) S m(-1), 486 x 10(3) S m(-1) and 510 x 10(3) S m(-1) for MAPbBr(3), MAPbCl(3) and MAPbI(3), respectively. This study provides valuable insights for optimizing the performance of perovskite solar cells. Understanding how dopants influence the electrical conductivity and photovoltaic properties of the perovskite material, this work will enable researchers to design and engineer more efficient and stable solar cell devices based on MAPbX(3) perovskites.