Highly Compact TiO₂ Films by Spray Pyrolysis and Application in Perovskite Solar Cells

Abstract

Transparent and pinhole free hole-blocking layers such as TiO 2 grown at low temperatures and by scalable processes are necessary to reduce production costs and thus enabling commercialization of perovskite solar cells. Here, the authors compare the transport properties of TiO 2 compact layers grown by spray pyrolysis from commonly used titanium diisopropoxide bisacetylacetonate ([Ti(OPr i ) 2 (acac) 2 ]) precursor to films grown by spray pyrolysis of TiCl 4 . Spray pyrolysis provides insights into the interdependence of precursor chemistry and electron transport properties of TiO 2 films and their influence on the performance of the perovskite solar cells. X-ray diffraction and X-ray photoelectron spectroscopy data confirm the chemical and structural composition of the obtained films. Thin film deposition at lower temperature (150 C) are conducted using TiCl 4 to evaluate the influence of crystal growth and topography by scanning electron microscopy and atomic force microscopy as well as thickness (profilometry) and transmittance (UV/Vis spectroscopy) on the power conversion efficiency of perovskite solar cells. TiO 2 compact layers grown from TiCl 4 enhance the power conversion efficiency by acting as superior electron transfer medium and by reducing hysteresis behavior, when compared to films grown using titanium diisopropoxide bisacetylacetonate. UV/Vis spectroscopy and external quantum efficiency studies reveal the correlation of transmittance on the power conversion efficiency.

Spray Pyrolyzed TiO2 Embedded Multi-Layer Front Contact Design for High-Efficiency Perovskite Solar Cells

“…Until now, a wide variety of metal oxides, such as ZnO, SnO 2 , TiO 2 , and WO 3 , have been investigated as electron transport materials (ETMs) ought to their high electron mobility and enhanced environmental stability [8,15,[20][21][22]. Amongst, TiO 2 is considerably popular due to its potential simple deposition, suitable energy level, and tunable electronic properties [23][24][25]. Furthermore, TiO 2 can produce a smooth film surface to improve charge transfer while maintaining the uniformity [19,23].…”

The Influence of the Thickness of Compact TiO2 Electron Transport Layer on the Performance of Planar CH3NH3PbI3 Perovskite Solar Cells

“…The titaniumoxide-based ETL is also a crucial investigation area reported in a number of studies [18][19][20][21][22]. The titanium dioxide blocking layer can be deposited by various methods: atomic layer deposition (ALD) [23], magnetron sputtering [24], spray pyrolysis [25], electrochemical deposition [26] and spin coating, where the latter is most commonly used. Due to the relatively high surface roughness of the FTO electrode, typically ca.…”

Synthesis and Thermal Behavior of Heteroleptic γ‐Substituted Acetylacetonate‐Alkoxides of Titanium

“…In order to have a monomer structure and increase the thermal stability, complexes based on disubstituted-diketonates of the general formula [Ti(OiPr) 2 (β-dik) 2 ] (β-dik = acac, 2,4-pentanedione; thd, 2,2,6,6-tetramethyl-3,5-heptanedione) have been extensively investigated as precursors for the production of TiO 2 thin films in the gas phase (over 200 patents mention their uses). [2,3] Mono-substituted β-diketonate dimer complexes of the general formula [Ti(OiPr) 3 (β-dik)] 2 are little employed because they are generally converted into di-substituted derivatives by a redistribution reaction of the ligand. [4] Such derivatives presented as common features high thermal stability for good transportation but lower volatility and mainly low reactivity.…”