Bifunctional Surface Engineering on SnO₂ Reduces Energy Loss in Perovskite Solar Cells

Abstract

Tin oxide (SnO2) has recently emerged as a promising electron transport layer for perovskite solar cells (PSCs) in light of the material’s optical and electronic properties and its low-temperature processing. However, SnO2 films are prone to surface defect formation, which results in energy loss in PSCs. We report that surface treatment using ammonium fluoride (NH4F) leads to reduced surface defects and that it also induces chemical doping of the SnO2 substrate simultaneously. The effects of NH4F treatment on SnO2 properties are revealed by surface chemical analysis, computational studies, and energy level investigations, and PSCs with the treatment achieve photovoltaic performance of 23.2% in light of higher voltage than in relevant controls.

Rubidium Fluoride Modified SnO2 for Planar n‐i‐p Perovskite Solar Cells

“…In addition, Figure 1b shows that Sn 3d peak shifts by about 0.3 eV towards a lower binding energy for the SnO 2 ‐RbF, indicating a change in electron cloud density around the Sn atoms because of the strong bonding between F and Sn when RbF is introduced into the bulk SnO 2 . [ 39,40 ] However, the Sn 3d peak of the SnO 2 /RbF shows almost no shift compared with the SnO 2 film, which implies the weak interaction between F and Sn atoms. This phenomenon indicates that the FSn bond may form before or during the annealing process, after that SnO 2 has crystalized and could hardly interact with F ions.…”

“…However, more and more groups found that the hysteresis still existed in the SnO 2 ‐based (commercial SnO 2 aqueous colloidal dispersion) PSCs unless modifying the SnO 2 surface or adding additives into the SnO 2 . [ 36–39 ] For example, Facchetti and co‐workers found non‐conjugated multi‐zwitterionic small‐molecule electrolytes could modify the SnO 2 /perovskite interface to passivate defects/traps and further restrain the non‐radiative recombination, which decreased its voltage loss and eliminated the hysteresis. [ 36 ] In addition, Zhang and co‐workers reported graphdiyne introduction into SnO 2 efficiently assisted perovskite crystallization, contributing to high‐quality perovskite films with a lower defect density.…”

cPCN-Regulated SnO2 Composites Enables Perovskite Solar Cell with Efficiency Beyond 23%

“…After optimization, the best device (0.1cm 2 ) is obtained with a PCE of 23.17%, a V OC as high as 1.126 V, a J SC of 24.9 mA cm −2 , and FF of 82.5%. It is one of the best performances in PSCs with modified SnO 2 [ 15 , 51 , 52 ]. The superior performance of PSCs with cPCN-treated SnO 2 is in line with the improved film quality and higher absorptions.…”

Highly Enhanced Efficiency of Planar Perovskite Solar Cells by an Electron Transport Layer Using Phytic Acid–Complexed SnO2 Colloids

“…[ 24 ] Jung et al used NH 4 F surface treatment to reduce the defect sites on the SnO 2 surface and obtained a higher PCE. [ 15 ] Furthermore, Liu et al modified SnO 2 by ethylene diamine tetra‐acetic acid (EDTA) chelating agent to realize an EDTA‐complexed SnO 2 ETL, which shows more superior electronic properties than the pristine SnO 2 ETLs. [ 26 ] However, the effect of defect passivation is limited owing to the weak interaction between the passivation molecules and the SnO 2 NCs, resulting in the agglomeration of SnO 2 NCs still exists.…”