Decoding the charge carrier dynamics in triple cation based perovskites solar cells

Deciphering charge carrier dynamics in perovskites solar cells (PSCs) and electrical merits are essential to further improve the performance and operational stability. We investigated the charge carrier dynamics in triple cation-based PSCs through temperature dependence electrochemical impedance spectra, thermal admittance spectroscopy, and space charge limited current (SCLC). The measured temperature dependence capacitance versus frequency (C-f) spectra reveal two kinds of activation process: (i) low-frequency at higher temperature (>260 K), and (ii) high-frequency at a lower temperature (< 260 K). The evaluated activation energy (EA) at a high temperature from all three experiments was found to be in the range of 0.255 – 0.266 eV, which corresponds to activate the migration of halide anion, whereas the low-temperature activation process stems from the trapping/de-trapping of electronic charges from shallow traps. The trap density of states in triple cation (1015 eV-1cm-3) was evaluated to be over two to six orders of magnitude lower than typically used single cation-based perovskites, while charge carrier mobility (5.76 × 10-3 cm2/V.s) evaluated from the SCLC technique was nearly an order of magnitude higher than single cation perovskites