Shallow and Deep Trap State Passivation for Low-Temperature Processed Perovskite Solar Cells

Abstract

While perovskite solar cells (PSCs) have emerged as promising low-cost solar power generators, most reported high-performance PSCs employ electron transport layers (ETLs, mainly TiO2) treated at high temperatures (≥450 °C), which may eventually hinder the development of flexible PSCs. Meanwhile, the development of low-temperature processed PSCs (L-PSCs) possessing performance levels comparable to those of high-temperature processed PSCs has actively been reported. In this study, L-PSCs with improved long-term stability and negligible hysteresis were developed through the effective passivation of shallow and deep traps in organic–inorganic hybrid perovskite (OIHP) crystals and at the ETL/OIHP interface. L-PSCs with alkaline chloride modification achieved state-of-the-art performance among reported L-PSCs (power conversion efficiency (PCE) = 22.6%) with a long-term shelf life. The origin of long-term stability and the efficient passivation of deep traps was revealed by monitoring the trap-state distribution. Moreover, the high PCE of a large-area device (21.3%, 1.12 cm2) was also demonstrated, confirming the uniformity of the modification.

Review of Interface Passivation of Perovskite Layer

“…Many passivation molecules directly neutralize the surface charges or dangling bonds to annihilate the corresponding electron traps [ 98 , 99 , 100 ], e.g., by introducing Lewis bases (such as thiourea) to coordinate with Pb 2+ on the surface and grain boundaries to reduce the defect density; some electron trap states can accept one of the Lewis-based defects on the surface of the perovskite through the Lewis acid molecule electron to be reduced [ 62 , 101 , 102 , 103 , 104 ]. The molecular hydrophilic chemical group and perovskite molecule combine to form a coordination bond, which is conducive to the transport of carriers [ 60 , 105 , 106 ].…”

Bulk Passivation and Interfacial Passivation for Perovskite Solar Cells: Which One is More Effective?

“…Reproduced with permission. [ 145 ] Copyright 2020, American Chemical Society. B) Elimination of the surface hydroxyl groups.…”

Extension of In-Gap Electronic-State Spectrum Extraction Technique Based on Transient Photo-Voltage Measurement

“…The density of trap states (DOS T ) distribution is one of the most important factors determining the power conversion efficiency (PCE) of perovskite solar cells (PSCs) [1][2][3][4][5][6] . It affects the carrier recombination and transport to hinder the enhancement of PCE [7][8][9][10] .…”

“…It affects the carrier recombination and transport to hinder the enhancement of PCE [7][8][9][10] . Recent years, people focus on the study of trap passivation [1][2][3][4][5] .…”

“…It affects the carrier recombination and transport to hinder the enhancement of PCE 7-Trap passivation reduces the amount of trap states to improve the PCE. To evaluate the passivation efficiency, we need to calculate the DOS T distributions of devices with and without passivation for compare 1,2,4,6 . There are few breakthroughs made in the DOS T extraction.…”