Improved photovoltaic performance of mesoporous perovskite solar cells with hydrogenated TiO2: prolonged photoelectron lifetime and high separation efficiency of photoinduced charge

Abstract

Hydrogenated titanium dioxide (H-TiO₂) nanocrystals and nanorods (H-TNRs) are successfully synthesized and employed as electron transfer materials in mesoscopic perovskite solar cells (PSCs). In comparison with PSCs based on untreated TiO₂, PSC devices based on H-TiO₂ exhibit a significantly greater photovoltaic performance with a solar-to-electric energy conversion efficiency of over 13%. A 15.79% increase in J_sc (17.29 mA cm⁻² to 20.02 mA cm⁻²) was observed in PSCs based on TiO₂ and H-TiO₂ nanopowders, and also there is a slight amplification of the open-circuit voltage (V_oc) from 0.92 V to 0.97 V. The H-TiO₂ nanocrystals exhibit a broader absorption band in the visible wavelength range, the donor density is increased and the band potential is shifted positively, which yield the enhanced driving force for electron injection thus elevating the current density of the PSCs. Moreover, it is elucidated that the electron behavior of the H-TiO₂ nanocrystals can prolong the photogenerated charge lifetime, slow down the recombination rate of the electron–hole pairs and elevate the photoinduced charge separation efficiency through surface photovoltage spectroscopy (SPS) and transient photovoltage measurement (TPV).