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Optimizing the oxidation time of Spiro-OMeTAD hole transport layer for enhanced performance in perovskite solar cells

Gltad Alas^a, Ya-li Zhu^a, Chen-hua Huang^a, Ru-yi Tang^a, Bao Asina^a, Lin-rui Zhang^a,b, Ying-Jie Li^a,b, Jun Ning^a,b,*, Hexig Alata^a,b,*

 
ABSTRACT:     Perovskite solar cells (PSCs) have great potential to achieve high-efficiency and low-cost photovoltaic devices. 2,2?,7,7?-tetrakis-(N,N-dip-methoxyphenylamine)-9,9?-spirobifluorene (Spiro-OMeTAD) is widely used as a hole transport layer (HTL) in high-performance PSCs. However, Spiro-OMeTAD has poor conductivity. To address this limitation, it is typically doped with hygroscopic additives, such as lithium bistrifluoromethylsulfonamide (Li-TFSI) and 4-tert-butylpyridine (tBP). Unfortunately, its inherent humidity sensitivity limits both performance and stability of PSCs. There are a few systematic investigations into the effect of Spiro-OMeTAD oxidation time on PSC performance. This study systematically investigates the influence of varying oxidation times on the photovoltaic performance in PSCs with Spiro-OMeTAD HTL. We fabricated PSCs with an indium tin oxide (ITO)/tin oxide (ceSnO2)/perovskite/Spiro OMeTAD/Silver (Ag) architecture. The oxidation time of the Spiro-OMeTAD layer was tuned between 24 and 168 h. It wasfoundthatanoxidationtimeof96hwasoptimumforthecrystallizationof Spiro-OMeTADfilm, therebyminimizing defect density and enhancing carrier transport. This results in a power conversion efficiency (PCE) of 16.80%. The optimal oxidation time effectively suppresses non-radiative recombination and improves the stability of PSC. Our f indings underscore the critical role of precise oxidation control in HTLs and provide a straightforward approach to boost PSC performance.

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* Corresponding author, E-mail: ningjun@imnu.edu.cn, alata@imnu.edu.cn

Received 16 Sep 2025, Accepted 4 Feb 2026