Microscopic Analysis of Inherent Void Passivation in Perovskite Solar Cells

Abstract

The presence of voids in perovskite solar cells influences the efficiency because of accelerated charge recombination. The induced electric field near voids due to band bending attracts photogenerated electrons and holes toward the voids, leading to carrier recombination. However, if the surface of the voids is coated by materials with a band gap higher than that of the perovskite layer, the strong electric field induced near the voids in the opposite way prevents carriers from recombining. We identified voids in the perovskite layer by using an electron beam-induced current technique and found the influence of field-assisted passivation by organic materials on the efficiency of the solar cell.

Vapor Exchange Deposition of an Air-Stable Lead Iodide Adduct on 19% Efficient 1.8 cm2 Perovskite Solar Cells

“…The XRD pattern of the intermediate phase exhibits a peak at 14.1° that is assigned to the β-phase perovskite; further, a very small diffraction peak is observed to range from 8.5° to 10.5°, indicating that the film forms an amorphous phase in the presence of DMI. The formation of an amorphous intermediate phase suppresses surface nucleation in bulk and accelerates heterogeneous nucleation at the bottom interface, which promotes the formation of vertically monolithic grains …”

“…The formation of an amorphous intermediate phase suppresses surface nucleation in bulk and accelerates heterogeneous nucleation at the bottom interface, which promotes the formation of vertically monolithic grains. 45 In the absence of stable adducts, the film's color changed from yellow to pale-gray during VED (Figure 6a), indicating the formation of a rough surface. When stable adducts were used, the film gradually became darker, especially in case of the DMI sample.…”

In operando x-ray imaging of nanoscale devices: Composition, valence, and internal electrical fields

“…Imaging both the internal electric fields and chemical composition of devices is thus an interesting prospect. Recently, electron beam–induced current measurements and Kelvin probe force microscopy have emerged as powerful tools to study the spatial variations of charge separation inside a device ( 4 , 5 ). Despite their strengths, there are several limitations imposed in terms of operating conditions, chemical sensitivity, energy tunability, penetration depth, as well as vacuum and sample preparation, which can be overcome using synchrotron radiation sources.…”

Synergistic Crystal and Interface Engineering for Efficient and Stable Perovskite Photovoltaics

“…[34,35] As reported in the literature, [36] most of the defects such as voids in the perovskite layer are located at the interface of the perovskite and back contact. For this purpose, we applied a voltage of 10 kV with a fixed current of 170 pA on top of the device to send the electrons passing through the gold back contact and reach the interface between the perovskite and the HTL.…”

“…The EBIC current of devices was extracted from the junction between the perovskite and spiro‐MeOTAD layers as a result of the generation of charge carriers from excitation of the perovskite by the 10 keV electron beam impinging on the sample . As reported in the literature, most of the defects such as voids in the perovskite layer are located at the interface of the perovskite and back contact. Consequently, passivation is a significant step to improve the device performance.…”