Charge Accumulation, Recombination, and Their Associated Time Scale in Efficient (GUA)_x(MA)_1–xPbI₃-Based Perovskite Solar Cells

Abstract

Here, we study the influence of guanidinium (GUA) ions on the open-circuit voltage (Voc) in the (GUA)x(MA)1–xPbI3 based perovskite solar cells. We demonstrate that incorporation of GUA forms electronic and ionic accumulation regions at the interface of the electron transporting layer and perovskite absorber layer. Our electrochemical impedance spectroscopy results prove that the formed accumulation region is associated with the enhanced surface charge capacitance and photovoltage. Furthermore, we also demonstrate the influence of the GUA ions on the enhanced interfacial and bulk electronic properties due to more efficient charge transfer between the bulk and interfaces and the reduced electronic defect energy levels.

Elucidation of the role of guanidinium incorporation in single-crystalline MAPbI3 perovskite on ion migration and activation energy

“…In our previous reports on GUA x MA 1Àx PbI 3 PSCs, we observed a complex impedance peak between 10 5 and 10 6 Hz and the corresponding time constant depicts the recombination kinetics in the cell, which is significantly suppressed upon GUA incorporation. 43,48 However, such high-frequency response is not observed in the present study. In turn, we observed that with incorporation of a small amount of the GUA cation in the MAPbI 3 crystal structure, the rate of change in the apparent time constant is significantly suppressed with a change in temperature.…”

“…41,42 Surprisingly, it was found that the incorporation of GUA in the MAPbI 3 perovskite structure enhances the hysteresis effect in comparison to the pristine MAPbI 3 based PSCs. 38,43 Initially, Yang et al assumed that GUA is not confined within the perovskite lattice but rather is weakly hydrogen-bonded to the under-coordinated ionic species mainly at grain boundaries. 38 They proposed that mobile GUA cations can migrate to the interfaces and screen the applied electric field leading to enhanced hysteresis in the device.…”

Crystallization Kinetics in 2D Perovskite Solar Cells

“…Moreover, the introduction of GA + to 2D perovskite not only increased the charge transport and diffusion length, but also formed an accumulation region of electrons and ions on the surface between the electron transport layer and the perovskite light‐absorbing layer, which led to an increase in V OC . [ 154 ]…”

Changes in the Electrical Characteristics of Perovskite Solar Cells with Aging Time

“…Perovskite solar cells (PSCs) have become the front runner in emerging thin-film solar cells, with power conversion efficiency (PCE) exceeding 25% owing to their low-cost solution processing and exciting optoelectronic features such as their high absorption coefficient, tunable stability, and superior carrier transportation properties [1][2][3][4][5][6][7][8]. Nevertheless, the key issue that hampers the commercialization of PSCs is device instability under light, moisture, and high-temperature exposure [9,10].…”