Decoding the charge carrier dynamics in triple cation-based perovskite solar cells

Abstract

Deciphering the charge carrier dynamics in perovskite solar cells (PSCs) and electrical merits is essential to further improve the performance and operational stability. We investigated the charge carrier dynamics in triple cation-based PSCs through temperature dependent electrochemical impedance spectroscopy, thermal admittance spectroscopy, and space charge limited current (SCLC). The temperature dependent capacitance versus frequency (C-f) spectra reveal two kinds of activation process, one at low frequency and high temperature (>260 K), and the other at high frequency and low 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 the activation of the migration of halide anions, while 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-based perovskites (1015 eV-1 cm-3) was evaluated to be over two to six orders of magnitude lower than that of typically used single cation-based perovskites, while the charge carrier mobility (5.76 × 10-3 cm2 V-1 s-1) evaluated from the SCLC technique was nearly an order of magnitude higher than that of single cation perovskites.