Hysteresis Improvement Enabled by Methylamine Post Treatment for Mesoporous NIP Perovskite Solar Cells

Chen-Tse Tsai^a, Tzu-Chien Wei^a

^aDepartment of Chemical Engineering, National Tsing Hua University, Hsinchu, 300044, Taiwan, Republic of China.

Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
Proceedings of Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics (IPEROP27)

Fukuoka, Japan, 2027 January 18th - 20th

Organizers: Zhanglin Guo and Tingli Ma

Poster, Chen-Tse Tsai, 092
Publication date: 22nd October 2026

Organic–inorganic halide perovskite solar cells (PSCs) have attracted considerable attention due to their excellent light absorption properties, efficient charge transport, and potential for low-cost solution processing. Among various device architectures, mesoporous n–i–p perovskite solar cells have demonstrated high power conversion efficiencies (PCEs), benefiting from effective electron extraction and favorable interfacial contact provided by the mesoporous electron transport layer. However, despite these advantages, current density–voltage (J–V) hysteresis remains a critical issue that affects the accurate evaluation of device performance. This phenomenon is characterized by differences between forward and reverse voltage scans and is commonly associated with ion migration, interfacial charge accumulation, and charge carrier recombination. In particular, the redistribution of mobile ionic species under an applied electric field can modify the internal electric field and interfacial charge dynamics, resulting in scan-dependent photovoltaic characteristics.

In this study, methylamine post-treatment (MATM) was introduced to improve the film quality and suppress hysteresis in mesoporous n–i–p perovskite solar cells. The treatment involves the interaction between methylamine and the perovskite material, inducing a transient intermediate state followed by recrystallization upon methylamine removal. This process can improve film uniformity, surface morphology, and crystallinity while reducing defect-related charge recombination. The effects of MATM on photovoltaic performance were investigated by comparing the forward and reverse J–V characteristics of untreated and MATM-treated devices. Particular attention was given to changes in open-circuit voltage (V_OC), fill factor (FF), power conversion efficiency (PCE), and hysteresis behavior.

Furthermore, electrochemical impedance spectroscopy (EIS) was employed to investigate the relationship between hysteresis and ion migration before and after MATM. By analyzing the impedance response over different frequency ranges, the charge transport and slow electrical processes associated with ionic motion and interfacial polarization were examined. In particular, the low-frequency impedance response was investigated to gain further insight into ion migration-related behavior and its possible contribution to J–V hysteresis.

The results indicate that MATM improves the photovoltaic performance of mesoporous n–i–p perovskite solar cells while reducing the discrepancy between forward and reverse J–V scans. Combined with EIS analysis, these findings provide further insight into the relationship between film quality, ion migration-related electrical processes, and hysteresis suppression. This study highlights the potential of methylamine post-treatment as an effective approach to improving the performance and reducing hysteresis in mesoporous perovskite solar cells.

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