Multi-functional Strategy: Ammonium Citrate-Modified SnO₂ ETL for Efficient and Stable Perovskite Solar Cells

Abstract

The tin oxide (SnO2) electron transport layer (ETL) plays a crucial role in perovskite solar cells (PSCs). However, the heterogeneous dispersion of commercial SnO2 colloidal precursors is far from optimized, resulting in dissatisfied device performance with SnO2 ETL. Herein, a multifunctional modification material, ammonium citrate (TAC), is used to modify the SnO2 ETL, bringing four benefits: (1) due to the electrostatic interaction between TAC molecules and SnO2 colloidal particles, more uniformly dispersed colloidal particles are obtained; (2) the TAC molecules distributed on the surface of SnO2 provide nucleation sites for the perovskite film growth, promoting the vertical growth of the perovskite crystal; (3) TAC-doped SnO2 shows higher electron conductivity and better film quality than pristine SnO2 while offering better energy-level alignment with the perovskite layer; and (4) TAC has functional groups of CO and N–H containing lone pair electrons, which can passivate the defects on the surface of SnO2 and perovskite films through chemical bonding and inhibit the device hysteresis. In the end, the device based on TAC-doped ETL achieved an increased power conversion efficiency (PCE) of 21.58 from 19.75% of the reference without such treatment. Meanwhile, the PSCs using the TAC-doped SnO2 as the ETL maintained 88% of their initial PCE after being stored for about 1000 h under dark conditions and controlled RH of 10–25%.

Additive engineering with sodium azide material for efficient carbon-based perovskite solar cells

“…The charge recombination resistance ( R rec ) is raised from 974.2 Ω to 1940.4 Ω compared to the pristine device, indicating effective electron–hole recombination reduction due to defect suppression, which complementarily explains the change in the perovskite photovoltaic device's performance characteristics. 22,35,36 In addition, EIS shows that the series resistance ( R s ) in the modified C-PSCs is 25.4 Ω, lower than 34.2 Ω obtained for the pristine C-PSCs, indicating lower current losses at the interfaces of the modified C-PSCs. Indeed, the FF and J SC improvements can be attributed to the boosted perovskite film quality, reduced non-radiative recombination, and facilitated charge extraction.…”

Device Structures of Perovskite Solar Cells: A Critical Review

“…Therefore, choosing the best‐suited ETL is crucial in optimizing PSCs’ PCE. [ 39 ] Some of the remarkable PSCs and their device structure and performance parameters are presented in Table 1 .…”

Poly(acrylic acid)‐Modified SnO2 Electron Transport Layer for Perovskite Solar Cells

“…[15] Figure 1b shows that both films from the pristine SnO 2 and the PAA modified SnO 2 precursors exhibited fine optical transmittance in the range from 400 to 800 nm, and the fine optical transmittance of ETLs are favorable for the light absorption of the perovskite layer. Meanwhile, the atom force microscopy (AFM) showed that the root-mean-square roughness (R q ) slightly increased from 2.42 to 2.79 nm (Figure 1c and 1d), the increased roughness of the PAA modified SnO 2 films may facilizing the nucleation and growth of perovskite films, [28] while decreasing the contact between ETL and perovskite.…”