Impact of interface defects on the band alignment and performance of TiO$_2$/MAPI/Cu$_2$O perovskite solar cells

TL;DR

This study investigates how interface vacancy defects in TiO$_2$/MAPI/Cu$_2$O perovskite solar cells affect band alignment and device performance, using DFT calculations and simulations to identify key defect impacts.

Contribution

It provides new insights into how specific vacancy defects influence band structure and doping effects at interfaces, guiding optimization of perovskite solar cell performance.

Findings

Vacancy defects induce doping effects that alter band alignment.

p-type TiO$_2$ doping and n-type Cu$_2$O doping significantly impact performance.

Perovskite interface doping affects charge collection efficiency.

Abstract

Optimizing the interfaces in perovskite solar cells (PSCs) is essential for enhancing their performance, improving their stability, and making them commercially viable for large-scale deployment in solar energy harvesting applications. Point defects, like vacancies, have a dual role, as they can inherently provide a proper doping, but they can also reduce the collected current by trap-assisted recombination. Moreover, they can play an active role in ion migration and degradation. Using {\it ab initio} density functional theory (DFT) calculations we investigate the changes in the band alignment induced by interfacial vacancy defects in a TiO$_2$/MAPI/Cu$_2$O based PSC. Depending on the type of the vacancy (Ti, Cu, O, Pb, I) in the oxide and perovskite materials, additional doping is superimposed on the already existing background. Their effect on the performance of the PSCs becomes visible, as shown by SCAPS simulations. The most significant impact is observed for $p$ type doping of TiO$_2$ and $n$ type doping of Cu$_2$O, while the effective doping of the perovskite layer affects one of the two interfaces. We discuss these results based on modifications of the band structure near the active interfaces and provide further insights concerning the optimization of electron and hole collection.