ADVANCED SCIENCE, 2024 (SCI-Expanded)
The enhancement of the photovoltaic performance upon the aging process at particular environment is often observed in perovskite solar cells (PSCs), particularly for the devices with 2,2 ',7,7 '-tetrakis(N,N-di(4-methoxyphenyl)amino)-9,9 '-spirobifluorene (spiro-OMeTAD) as hole transporting material (HTM). In this work, for the first time the effect of aging the typical n-i-p PSCs employing nickel phthalocyanine (coded as Bis-PF-Ni) solely as dopant-free HTM is investigated and as an additive in spiro-OMeTAD solution. This study reveals that the prolong aging of these devices at dry air condition (RH = 2%, 25 degrees C) is beneficial for the improvement of their performances. Various bulk and surface characterization techniques are utilized to understand the factors behind the spontaneous efficiency enhancement of the devices after storage. As a result, the changes in properties of the Bis-PF-Ni layer are observed and at perovskite/Bis-PF-Ni interface, which ultimately improves the charge transport and reduces non-radiative recombination. In addition, the devices with Bis-PF-Ni HTM reveal enhanced long-term ambient and thermal stability compared to the PSCs based on doped spiro-OMeTAD. This study reveals the effect of aged Bis-PF-Ni HTM on the overall performance of PSCs. The observed self-enhancement of the PCE is attributed to the enhanced conductivity, better band alignment of Bis-PF-Ni, reduces trap-assisted recombination, and improves charge transport. The devices demonstrated superior ambient and thermal stability. image