Impedance Spectroscopic Analysis of Lead Iodide Perovskite-Sensitized Solid-State Solar Cells

Abstract

Mesoscopic solid-state solar cells based on the inorganic-organic hybrid perovskite CH3NH3PbI3 in conjunction with the amorphous organic semiconductor spiro-MeOTAD as a hole transport material (HTM) are investigated using impedance spectroscopy (IS). A model to interpret the frequency response of these devices is established by expanding and elaborating on the existing models used for the liquid and solid-state dye-sensitized solar cells. Furthermore, the influence of changing the additive concentrations of tert-butylpyridine and LiTFSI in the HTM and varying the HTM overlayer thickness on top of the sub-micrometer thick TiO2 on the extracted IS parameters is investigated. The internal electrical processes of such devices are studied and correlated with the overall device performance. In particular, the features in the IS responses that are attributed to the ionic and electronic transport properties of the perovskite material and manifest as a slow response at low frequency and an additional RC element at intermediate frequency, respectively, are explored.

Origin and elimination of photocurrent hysteresis by fullerene passivation in CH3NH3PbI3 planar heterojunction solar cells

“…IS has been widely utilized in many photovoltaic systems, such as dye-sensitized solar cells 32 , organic solar cells 33 and perovskite solar cells 34,35 . The technique is a valuable tool to decouple electronic parameters, such as capacitances and resistances in photovoltaic devices, by analysing the frequency-dependent alternating current response with appropriate equivalent circuits.…”

Ionic Reactivity at Contacts and Aging of Methylammonium Lead Triiodide Perovskite Solar Cells

“…Particularly intriguing is the hysteresis features in the response of the current density-voltage ( V J − ) curves [10][11][12][13] that have been related to a number of different explanations, as ferroelectric properties of the perovskite materials, [14][15][16] delayed electronic trapping processes, [17] or slow ion migration. [11,18,19] The recognition that the solar cell performance is heavily affected by time scale of the measurement and preconditioning procedures [9,17,20,21] has raised many concerns about the stability of the device and reliability for long time operation.…”

Optoelectronic Studies of Methylammonium Lead Iodide Perovskite Solar Cells with Mesoporous TiO2: Separation of Electronic and Chemical Charge Storage, Understanding Two Recombination Lifetimes, and the Evolution of Band Offsets during J–V Hysteresis

“…There is also debate about how to correctly measure the recombination and transport times, the charge density, and even the correct measurement of efficiency. [5][6][7][8][9][10][11][12][13][14][15][16][17] The debate about characterization centers on the interpretation of various time constants that can be measured by optical and electrical means. These time constants range from <1 µs to >100 µs.…”