Impact of sol aging on TiO2 compact layer and photovoltaic performance of perovskite solar cell

Abstract

Perovskite solar cells are known to have a power conversion efficiency dependent on subtle variation in chemical composition and crystal and microstructures of materials, processing conditions, and device fabrication procedures and conditions. The present work demonstrates such strong dependence of power conversion efficiency on a TiO2 film made of the same sol with various aging time. A dense and conformal TiO2 film was prepared by sol-gel method, and the influences of its surface morphology and thickness on performance of perovskite solar cells have been investigated. The surface morphology and thickness of the TiO2 film were tuned by adjusting the aging time of sol, resulting in enhanced short-circuit current density and fill factor of the perovskite solar cells due to increased coverage and roughness of perovskite films, light refraction, and effective charge recombination blocking effect, which were verified by means of the light absorption spectra, photoluminescence of perovskite films with and without hole transport layer, cyclic voltammogram, and electrochemical impedance spectra. The cells with a dense and conformal TiO2 compact layer derived from the sol aged for 4 h exhibit a power conversion efficiency of 15.7%, 50% higher than the efficiency based on TiO2 layer derived from 0 h aging sol and 3 times of the efficiency with TiO2 layer made from 8 h aged sol.

Engineering oxygen vacancy on rutile TiO2 for efficient electron-hole separation and high solar-driven photocatalytic hydrogen evolution

“…Since Fujishima and Honda [5][6][7] discovered hydrogen production from water splitting on TiO 2 for the first time, it is considered as the most promising photocatalyst candidate due to nontoxicity, high stability and low-cost [8][9][10]. Therefore, TiO 2 is widely used in photocatalytic degradation of pollutants, photocatalytic hydrogen production, solar cells, photoelectrochemical devices, and so on [11][12][13][14]. It is well-known that TiO 2 has three different crystal phases, anatase, brookite and rutile [15].…”

An annealing-free aqueous-processed anatase TiO2 compact layer for efficient planar heterojunction perovskite solar cells

“…Among them, sol-gel methods are arguably the most widely adopted routes for depositing TiO 2 films owing to ease in fabrication and low cost. 4,11,[27][28][29] Nevertheless, the as-prepared TiO 2 films via the sol-gel methods are generally amorphous and therefore exhibit poor electrical conductivity, which incurs negative impacts on the performance of PSCs. 11,30 Strategies have been developed to enhance the electrical properties of TiO 2 films via optimising their morphology, doping and composition; these strategies include surface modification of TiO 2 with TiCl 4 treatment, ozone (O 3 ) treatment, 31,32 and doping modification of the TiO 2 film with an appropriate substitution of Li + , Mg 2+ , Al 3+ , Y 3+ , and Nb 5+ .…”

Advanced partial nucleation for single-phase FA0.92MA0.08PbI3-based high-efficiency perovskite solar cells

“…First, the high annealing temperature (~150°C) led to the decomposition of methylammonium iodine (MAI) molecules into CH 3 I and NH 3 gas, where poor surface morphology of the film was usually observed [6]. An increase in the FA + content might have benefited the thermal stability, but the undesired non-perovskite (δ-phase) by-product, δ-FAPbI 3 , was formed, which compromised the phase purity of the obtained FA x MA 1−x PbI 3 [5,7]. The observed defects in mixed-cation (MAFA) perovskite usually derive from the impurity phase and poor film morphology, which induce non-radiative recombination and low carrier mobility [8][9][10].…”