A Promising Passivation Strategy using Hydroxyethyl Cellulose for Enhancing the Performance of Inorganic-based Perovskite Solar Cells

Inorganic perovskite solar cells (PSCs) based on CsPbBr<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> have garnered significant attention due to their simple fabrication and excellent stability. However, the presence of interfacial defects within these devices has been reported to hinder their performance. This research presents a novel interfacial engineering approach utilizing hydroxyethyl cellulose (HEC) as a passivation layer. This study investigates the influence of HEC passivation on the efficiency of CsPbBr<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> based PSC devices comprising FTO/compact$\mathrm{TiO}_{2} /$ mesoporous- $\mathrm{TiO}_{2} / \mathrm{CsPbBr}_{3} /$ carbon. The $\quad$ PSCs performance was analyzed in the presence of HEC, which was deposited either before and after the formation of $\mathbf{C s P b B r}_{3}$ perovskite layer. Optical spectroscopy analysis revealed that HEC modification after perovskite deposition resulted in higher absorption within the visible light range compared to unmodified devices. Furthermore, the PSC constructed by incorporating HEC after CsPbBr<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> deposition exhibited the best performance with PSC constructed by incorporating HEC after CsPbBr<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> deposition exhibited the best performance with an average PCE of $3.06 \pm 0.25 \%$ and an average Voc, Jsc, and FF of $1.29 \pm 0.02 \mathrm{~V}, 4.13 \pm 0.31 \mathrm{~mA} / \mathrm{cm}^{2}$, and $57.13 \pm 0.50 \%$, respectively. Among PSC devices, the HEC passivated device significantly showed superior properties, wherein the unmodified PSC produced a PCE of $1.27 \pm 0.07 \%$ with a Voc of $0.94 \pm 0.01 \mathrm{~V}$. Electrochemical impedance spectroscopy also demonstrated that PSC with HEC deposited after $\mathbf{C s P b B r}{ }_{3}$ layer exhibited a relatively high recombination resistance of $1.42 \times 10^{6}$ ohm. This overall enhancement suggests that the passivation strategy using HEC has effectively suppressed carrier recombination within the CsPbBr<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> layer, thereby leading to improved device performance.