Suppressing Shallow Defect of Printable Mesoscopic Perovskite Solar Cells with a N719@TiO2 Inorganic-Organic Core-Shell Structured Additive

Shallow defects are one of the energy states that trap photoexcited electrons leading to charge recombination and limit the increase in the photocurrent of perovskite solar cells (PSCs). Due to the large perovskite thickness and uncontrollable crystallization processes, suppressing shallow defects, especially methylamine (MA) vacancies, has become a key challenge for fully printable PSCs. Herein, nano-TiO2 is unprecedentedly used to load the commercial dye N719, forming N719@TiO2 nanoparticles, which crucially improves the passivation effect of MA vacancies on the surface of perovskite and charge extraction, by the unbounded carboxyl group of N719 as a shell on the surface of TiO2. Meanwhile, the core TiO2 serves as a centre to bind the dyes, assisting the perovskite crystallization and enhancing the passivation effect. It is found that the charge extraction increases to 1.8007 x 10(-9) C for the devices based on N719@TiO2 from 1.5507 x 10(-9) C for the control group. Simultaneously, the short-circuit current density (J(sc)) is significantly enhanced to 23.58 mA cm(-2) in the device containing N719@TiO2 over that of the control device (21.95 mA cm(-2)). This opens up a novel pathway to reduce shallow defects in PSCs via organic passivator with carboxyl anchoring group loaded on n-type semiconductors (nano-TiO2).