Carrier-Activated Polarization in Organometal Halide Perovskites

Abstract

Organometal halide perovskite solar cells exhibit a strong polarization effect under light illumination. This unique property, although widely observed, has not been well understood. In this work, we carried out a systematic investigation on this phenomenon by varying the perovskite composition and device configurations. We find that the light-enhanced strong polarization is a general phenomenon that occurs in all tested perovskite materials. The organic molecular dipoles affect the polarization at high frequency range, while the photoexcited free carriers and the interface between perovskite and its neighboring layers dominate the low-frequency response. In particular, our study suggests that the giant low-frequency capacitance enhancement originates from native defects and their accompanying defect dipoles, which need to be activated by photogenerated charge carriers. The high flexibility of the perovskite lattice facilitates the formation of these defects, and the dipole effect is enhanced at the interface regions where an electric double-layer capacitor is formed. This work sheds light on the understanding of the light-induced polarization mechanisms of perovskite materials.

Thin Film Electrochemical Capacitors Based on Organolead Triiodide Perovskite

“…Figure 7 a,b presents the light and dark CV profi les of the butanol cell and the MAI/butanol cell, respectively. The increase of C 2 may be associated with a few different mechanisms, e.g., increase of fi rm conductivity and polarizability, carrier activated interface defect dipoles, [ 15 ] etc. Such reversible change is associated with a reversible increase of C 2 and C 3 under light, as shown in Figure 7 c,d.…”

“…The increase of C 3 may result from light-induced enhancement of the conductivity and polarizability [ 15,16 ] of the perovskite layer. The increase of C 3 may result from light-induced enhancement of the conductivity and polarizability [ 15,16 ] of the perovskite layer.…”

Cadmium Sulfide Quantum Dots–Organometallic Halide Perovskite Bilayer Electrode Structures for Supercapacitor Applications

“…Moreover, maintaining the pseudo‐rectangular shapes in all the CV curves, even at low rate, indicates presence of reasonably rapid electron transfer process. The distortion observed in the CV curves at different scan rates is probably due to reversible change which may be associated with a few different mechanisms, e. g., increase of film conductivity and polarizability, carrier activated interface defect dipoles, . The specific capacitance of each device at different scan rate is plotted in Figure c and the values are listed in Table .…”

“…The distortion observed in the CV curves at different scan rates is probably due to reversible change which may be associated with a few different mechanisms, e. g., increase of film conductivity and polarizability, carrier activated interface defect dipoles,. [36,37] The specific capacitance of each device at different scan rate is plotted in Figure 2c and the values are listed in Table 1. The highest specific areal capacitance is obtained when the scan rate is 0.01 V/s, in each case.…”

“…It serves both the purpose of electrolyte at the CdS/Perovskite interface and electrode at the perovskite/electrolytes interface . Also, organometallic halide perovskites can provide more active sites for the electrochemical reactions, shortening the pathways for transport of the charges or ions …”