Interface engineering at electron transport/perovskite layers using wetting mesoporous titanium dioxide to fabricate efficient and stable perovskite solar cells

Abstract

Summary The unique photovoltaic features of perovskites have encouraged researchers to use them as an active layer for solar cell applications. Recombination issue at electron transport layer (ETL)/perovskite interface is one of the reasons for performance reduction in perovskite solar cells (PSCs) and need to address. Hereof, we developed a simple and cheap method to modify this interface by wetting the mesoporous TiO2 ETL using mixed solvents of γ‐butyrolactone (GBL) and dimethyl sulfoxide (DMSO). With optimization of the ratio of GBL and DMSO, our results showed a smoother perovskite layer with fewer pinholes on it. In addition, ETL wetting affected perovskite grain sizes and passivated grain boundaries in it. The mentioned reasons reduced carriers' trap centers in the perovskite film and suppressed charge recombination processes within PSCs. The improved crystalline properties of the modified perovskite layer facilitate electron extraction at ETL/perovskite interface and reduce charge accumulation, which brings a champion efficiency of 18.72% for the treated devices higher than that of 15.21% for the untreated devices. Moreover, due to the boosted hydrophobic property of the modified perovskite film, the stability behavior of the related PSCs was improved remarkably.

Ionic Liquid Passivator for Mesoporous Titanium Dioxide Electron Transport Layer to Enhance the Efficiency and Stability of Hole Conductor-Free Perovskite Solar Cells

“…Such a trend was also established by Khaleel and Ahmed; they demonstrated the wetting role of the solvent modification of ms-TiO 2 ETL in the spin-coating fabrication method. 24 Cross-section FE-SEM images of perovskite layers with control or TMAOHmodified ETLs are shown in Figure 3c,d. The thickness of both perovskite layers is equal to 350 nm.…”

“…It implies that, under optimal modification conditions, a more compact and defects-free perovskite film forms over the ms-TiO 2 film. Such a trend was also established by Khaleel and Ahmed; they demonstrated the wetting role of the solvent modification of ms-TiO 2 ETL in the spin-coating fabrication method . Cross-section FE-SEM images of perovskite layers with control or TMAOH-modified ETLs are shown in Figure c,d.…”

“…Many techniques to address difficulties associated with the ETL/perovskite interfaces and ensure high performance have been reported. The deposition of an interfacial modifier layer between TiO 2 and perovskite, such as lanthanum salt, ZnO, or ZnS, is one of the approaches utilized to optimize carrier transfer dynamics and prevent the backflow of electrons, thereby reducing interfacial recombination. − Some ETL/perovskite interface treatments such as CO 2 plasma, ultraviolet-ozone, ETL additive engineering, and wet chemical methods have been used, which have led to significant enhancements in surface hydrophilicity, conductivity, and suppressed trap state density. − Huang and co-workers used a tetramethylammonium hydroxide (TMAOH) modifier to improve the electrical properties at the FTO/perovskite interface for ETL-free PSCs. The enhanced cell performance could be attributed to the improved charge collection, lower trap density, and decreased charge recombination at the FTO/perovskite interfaces, as well as in the perovskite film .…”

Charge transport materials for mesoscopic perovskite solar cells

“…As a result, suppressed carrier recombination and increased electron extraction were obtained leading to an enhnanced PCE of 18.72% compared to 15.21% for the untreated cells. 97 Alternatively, TiO 2 surface activation upon deep UV light (l = 254 nm) irradiation was proposed as a feasible strategy to improve its surface wetting properties and facilitate growth of a denser perovskite film with a reduced number of pinholes and consequently with an improved cell PCE. 98 UV light was also effective in removing organic binders from TiO 2 resulting in a stabilized efficiency of 18.2%.…”

Tuning the Pore Structures in TiO2 Thin Films by Polymer Templates for High-Performance Perovskite Solar Cells

“…ETLs typically consist of various semiconductor metal oxides, such as TiO 2 , , ZnO, SnO 2 , − CdS, , and Al 2 O 3 ; improving the quality of ETLs remains a major challenge for achieving high-stability and high-performance PSCs. , Among the available photocatalysts, TiO 2 is the most widely utilized material in PSCs owing to its advantages eco-friendliness, easy fabrication, low cost, chemical stability, and high PCEs . TiO 2 is used as an electron transport material in promising photovoltaic solar cells with various nanostructures such as nanowires, nanoparticles (NPs), or well-organized mesoporous structures.…”