Impact of a Mesoporous Titania–Perovskite Interface on the Performance of Hybrid Organic–Inorganic Perovskite Solar Cells

Abstract

We report on the optimization of the interfacial properties of titania in mesoscopic CH3NH3PbI3 solar cells. Modification of the mesoporous TiO2 film by TiCl4 treatment substantially reduced the surface traps, as is evident from the sharpness of the absorption edge with a significant reduction in Urbach energy (from 320 to 140 meV) determined from photothermal deflection spectroscopy, and led to an order of magnitude enhancement in the bulk electron mobility and corresponding decrease in the transport activation energy (from 170 to 90 meV) within a device. After optimization of the photoanode–perovskite interface using various sizes of TiO2 nanoparticles, the best photovoltaic efficiency of 16.3% was achieved with the mesoporous TiO2 composed of 36 nm sized nanoparticles. The improvement in device performance can be attributed to the enhanced charge collection efficiency that is driven by improved charge transport in the mesoporous TiO2 layer. Also, the decreased recombination at the TiO2–perovskite interface and better perovskite coverage play important roles.

Engineering of the Electron Transport Layer/Perovskite Interface in Solar Cells Designed on TiO2 Rutile Nanorods

“…The average value increases from 0.85 V for the reference device to 1.09 V for the dual modification. This result may be ascribed to the reduction of the electronic disorder at the ETL/perovskite interface . In general, the “electronic disorder” can be interpreted as a measure of the distribution of the electronic density of states (DOS).…”

“…In the past few years, organic–inorganic hybrid halide perovskite materials have come into focus due to their unique optoelectronic properties such as strong visible light absorbance and high carrier mobility . The implementation of this class of materials into solar cells has led to a new generation of rapidly developing photovoltaic technologies.…”

“…by passivation of the TiO 2 surface defects and trap states . To this end, titanium tetrachloride (TiCl 4 ) treatment, has been reported as a most efficient approach to improve TiO 2 electron transport ability: it forms at the treated surface a nm‐thick layer of TiO 2 anatase nanoparticles (NPs, with size in the 5–10 nm range) that typically favors a more efficient charge extraction across the ETL/perovskite interface, thereby limiting photon losses ascribed to charge recombination in the light absorber …”

Monovalent Cation Doping of CH₃NH₃PbI₃ for Efficient Perovskite Solar Cells

“…The full conversion of lead halide into perovskite in the second step is essential to achieve the highest light absorption1617, and we showed that the monovalent cation halide additives ( e.g., NaI and CuBr) result in a complete conversion. Furthermore, the complete coverage of the mesoporous titania layer with the perovskite over-layer is vital to eliminate potential recombination between the hole transport layer ( e.g., Spiro OMETAD) and the electron transport layer ( e.g., mesoporous TiO 2 )23. We illustrated that adding the monovalent cation halides ( e.g., CuI and AgI) can improve the surface coverage of the perovskite capping layer, which leads to a higher open circuit voltage for the device.…”

Deformation of Mesoporous Titania Nanostructures in Contact with D2O Vapor

“…Over the last decades mesoporous titania has gained considerable research interest for applications in catalysis, photovoltaics, and rechargeable lithium‐ion batteries . The great success is closely related to its superior chemical stability, large surface‐to‐volume ratio, tunable pore size, and having a wide bandgap .…”