Low-Temperature Plasma-Assisted Atomic-Layer-Deposited SnO₂ as an Electron Transport Layer in Planar Perovskite Solar Cells

Abstract

In this work, we present an extensive characterization of plasma-assisted atomic-layer-deposited SnO2 layers, with the aim of identifying key material properties of SnO2 to serve as an efficient electron transport layer in perovskite solar cells (PSCs). Electrically resistive SnO2 films are fabricated at 50 °C, while a SnO2 film with a low electrical resistivity of 1.8 × 10–3 Ω cm, a carrier density of 9.6 × 1019 cm–3, and a high mobility of 36.0 cm2/V s is deposited at 200 °C. Ultraviolet photoelectron spectroscopy indicates a conduction band offset of ∼0.69 eV at the 50 °C SnO2/Cs0.05(MA0.17FA0.83)0.95Pb(I2.7Br0.3) interface. In contrast, a negligible conduction band offset is found between the 200 °C SnO2 and the perovskite. Surprisingly, comparable initial power conversion efficiencies (PCEs) of 17.5 and 17.8% are demonstrated for the champion cells using 15 nm thick SnO2 deposited at 50 and 200 °C, respectively. The latter gains in fill factor but loses in open-circuit voltage. Markedly, PSCs using the 200 °C compact SnO2 retain their initial performance at the maximum power point over 16 h under continuous one-sun illumination in inert atmosphere. Instead, the cell with the 50 °C SnO2 shows a decrease in PCE of approximately 50%.

A Review of Perovskites Solar Cell Stability

“…Kuang et al introduced a PCBM interfacial layer between the SnO 2 and the perovskite significantly reduced the hysteresis. The SnO 2 deposited at 200 °C exhibted a more stable cell performance more than 16 h under continuous AM 1.5G illumination . Huang and co‐workers reported improved device efficiency from 14.05% to 16.87% with enhanced stability by introducing dopamine (DA) self‐assembled monolayer (SAM) on the top of the SnO 2 ETL to modify the SnO 2 /perovskite interface .…”

Solvent‐Assisted Low‐Temperature Crystallization of SnO2 Electron‐Transfer Layer for High‐Efficiency Planar Perovskite Solar Cells

“…Despite, plasma‐assisted ALD enhanced the crystallinity of SnO 2 , the necessary fabrication temperature was as high as 200 °C . In another attempt, sol‐gels of SnCl 2 ,·2H 2 O, or SnCl 4 ·5H 2 O was spin‐coated, followed by ≈180 °C anneal .…”

Chlorine‐modified SnO2 electron transport layer for high‐efficiency perovskite solar cells

“…It has attracted tremendous research efforts for its high transmittance, suitable bandgap, matched energy level, high electron mobility, and low temperature preparation. Significant efforts have been devoted to developing highly efficient PSCs by utilizing a SnO 2 ETL . Thus far, the certified efficiency of cells with a SnO 2 ETL has reached 23.3%, the highest efficiency for the planar‐type PSCs reported to date; however, based on the Shockley‐Queisser theory, the theoretical PCE limit is 30.5%.…”

“…Significant efforts have been devoted to developing highly efficient PSCs by utilizing a SnO 2 ETL. [28][29][30][31][32][33][34][35][36] Thus far, the certified efficiency of cells with a SnO 2 ETL has reached 23.3%, the highest efficiency for the planar-type PSCs reported to date 37 ; however, based on the Shockley-Queisser theory, the theoretical PCE limit is 30.5%. The main reason for PCE loss is carrier recombination.…”