Water‐Based TiO₂ Nanocrystal as an Electronic Transport Layer for Operationally Stable Perovskite Solar Cells

Abstract

Halide perovskite solar cells (PSCs) provide a new opportunity for next‐generation photovoltaic applications. However, traditional low‐temperature solution‐processed TiO2 that acts as an electron transport layer for PSCs shows an inferior stability compared with solar cells based on high‐temperature (typically 500 °C) TiO2; however, the high‐temperature process is energy consuming and is not compatible with flexible device processing. Traditional TiO2 nanoparticles made from titanium tetrachloride dispersed in an organic solvent usually have many organic molecules attached on their surface that lead to the formation of deep‐level defect states during long‐term operations. Herein, environmentally friendly, water‐based Cl‐passivated TiO2 nanoparticles (W‐TiO2) are invented, and surface organic molecules are removed by a vacuum rotary evaporation process. W‐TiO2‐based PSCs can reach up to a 20.5% power conversion efficiency with reduced hysteresis and can maintain 80% of their initial performance after 500 h of continuous operation under 1 sun illumination at the maximum power point. This improved performance is ascribed to the organic‐molecule‐free and Cl‐passivated surfaces. The water‐based TiO2 nanoparticle dispersion also offers a convenient and universal way to introduce other passivation agents to further improve the photovoltaic performance of PSCs.

Halogen Engineering for Operationally Stable Perovskite Solar Cells via Sequential Deposition

“…For the preparation of Spiro‐OMeTAD solution, 73.4 mg Spiro‐OMeTAD, 17.6 µL Li‐TFSI solution (520 mg Li‐TFSI in 1 mL ACN), and 28.8 µL 4‐TBP were mixed in 1 mL chlorobenzene and stirred overnight. The water‐based TiO 2 colloid precursor was prepared according to previous work . Briefly, the TiO 2 ‐Cl nanoparticles were synthesized following modified nonhydrolytic sol–gel method and the nanocrystals sediment were dispersed in ultrapure water to make a suspension.…”

TiO2 Colloid‐Spray Coated Electron‐Transporting Layers for Efficient Perovskite Solar Cells

“…Owing to its advantages (e.g., good transparency, favorable bandgap edge positions in relation to perovskites, environmental stability, and the feasibility of the solution processing with low-fabrication costs), TiO 2 has been widely adopted for the fabrication of high-efficiency PSCs. [9][10][11][12][13][14] An additional layer of thin mesoporous TiO 2 (mp-TiO 2 ) has been generally used to compensate the deficient charge collection efficiency, since of PSCs) by spray coating. Most spray coating for the deposition of inorganic ETLs is done using SnO 2 nanoparticles, but the maximum efficiency is still less than 20%.…”

Spin Coating Immobilisation of C-N-TiO2 Co-Doped Nano Catalyst on Glass and Application for Photocatalysis or as Electron Transporting Layer for Perovskite Solar Cells

“…The engineering of nanomaterials effective for both photo catalysis and photovoltaic applications is one of the challenging tasks in material science; nevertheless, various attempts were made in recent years [72][73][74]. Despite the photocatalysis scenarios and their benefits previously discussed, solar cell technologies are considered as outstanding prospects for renewable energy harvesting.…”