Hydrolysis-Regulated Chemical Bath Deposition of Tin-Oxide-Based Electron Transport Layers for Efficient Perovskite Solar Cells with a Reduced Potential Loss

Abstract

The high electron mobility, wide band gap, and chemical stability of n-type SnO2 have facilitated its use as an ideal electron transport layer (ETL) for perovskite solar cells (PSCs). However, the tendency of SnO2 to aggregate during film formation leads to poor morphology and low reproducibility. Despite important advances in the application of SnO2 for PSCs, a thorough understanding of material control over aggregation is lacking. Herein, aggregation-regulated SnO2 films are directly deposited on a fluorine-doped tin oxide glass surface via chemical bath deposition using retarding agents with multiple functional OH groups. Density functional theory calculations confirm the increase in stabilized binding energies of the Sn precursors by the retarding agents. Investigation of the morphology and topography of the SnO2 films reveals that manipulating the physicochemical properties of interacting molecules regulates SnO2 particle aggregation. The chemical states and energy-band properties of the fabricated SnO2 films are found to depend on the retarding agent used in the Sn precursors. The aggregation-regulated SnO2 layer prepared using glycerol exhibits an optimal morphology, a few oxygen vacancies, and a high work-function energy level. A device fabricated using the glycerol–SnO2 film as an ETL achieves a high efficiency of 21.8%, negligible hysteresis, and a reduced potential loss.

Alkali Metal Cations Modulate the Energy Level of SnO2 via Micro-agglomerating and Anchoring for Perovskite Solar Cells

“…However, the SnO 2 -Li film has increased roughness as AFM indicated due to ultralarge micron particles. In Figure S4, it is found that exposed FTO is present in the SnO 2 film, which is verified by other researchers on SnO 2 films prepared at low temperatures. , Therefore, a better coverage of reconstituted SnO 2 -Na reduces the pinholes and cracks at the surface, which may resist leakage current and carrier recombination loss . Then, the transmission of SnO 2 films is measured in Figure S5.…”

“…30,31 Therefore, a better coverage of reconstituted SnO 2 -Na reduces the pinholes and cracks at the surface, which may resist leakage current and carrier recombination loss. 32 Then, the transmission of SnO 2 films is measured in Figure S5. SnO 2 -Na films cause no transmission loss.…”

Alleviating Interfacial Recombination of Heterojunction Electron Transport Layer via Oxygen Vacancy Engineering for Efficient Perovskite Solar Cells Over 23%

“…This observation corroborates that the surface energy of the t-SnO 2 layers exerted at the perovskite layer is consistent for the heterojunction bilayers and possibly originates from the equivalent quality of the t-SnO 2 layers. [23] To elucidate the discrete behavior observed in the PSCs, dark J-V curves were investigated by performing fast J-V scans to obtain sheer electrical signals across a device without the slow time component, which may be related to ionic movement or a slow displacement of charge. [40] Figure 3a-d shows the dark J-V curves of the PSCs measured at a scan rate of 1000 mV s -1 .…”

“…[22] However, this technique is prone to generate an imperfect morphology with pinholes and cracks causing nonradiative recombination. [23,24] In contrast, bilayer structures appear competitive in terms of interfacial engineering for better charge extraction because of the passivation by a sequential layer synergically with enhanced band alignment. [25,26] Specifically, homojunction bilayers were sequentially constructed by depositing different SnO 2 layers.…”

Industrially Compatible Fabrication Process of Perovskite-Based Mini-Modules Coupling Sequential Slot-Die Coating and Chemical Bath Deposition

“…Due to the relatively slow deposition rates, an industrial CBD process has to be performed in parallel coating a large number of conductive oxide plates simultaneously. Recently, the deposition of SnO 2 using CBD has shown outstanding results for PSCs in terms of device efficiency (> 25%) as well as stability on both small cells ,, and mini-modules . This level of performance clearly demonstrates that SnO 2 is very well suited for being implemented into a perovskite device; however, the chemical mechanism that drives its deposition remains unclear.…”