Optimization of SnO2 electron transport layer for efficient planar perovskite solar cells with very low hysteresis

Nanostructured tin oxide (SnO2) is a very promising electron transport layer (ETL) for perovskite solar cells (PSCs) that allows low-temperature processing in the planar n-i-p architecture. However, minimizing current-voltage (J-V) hysteresis and optimizing charge extraction for PSCs in this architecture remains a challenge. In response to this, we study and optimize different types of single- and bilayer SnO2 ETLs. Detailed characterization of the optoelectronic properties reveals that a bilayer ETL composed of lithium (Li)-doped compact SnO2 (c(Li)-SnO2) at the bottom and potassium-capped SnO2 nanoparticle layers (NP-SnO2) at the top enhances the electron extraction and charge transport properties of PSCs and reduces the degree of ion migration. This results in an improved PCE and a strongly reduced J-V hysteresis for PSCs with a bilayer c(Li)-NP-SnO2 ETL as compared to reference PSCs with a single-layer or undoped bilayer ETL. The champion PSC with c(Li)-NP-SnO2 ETL shows a high stabilized PCE of up to 18.5% compared to 15.7%, 12.5% and 16.3% for PSCs with c-SnO2, c(Li)-SnO2 and c-NP-SnO2 as ETL, respectively.

Automated summary

The use of a bilayer c(Li)-NP-SnO2 ETL can enhance electron extraction and charge transport properties for perovskite solar cells, reducing J-V hysteresis and improving stability PCE compared to single-layer or undoped bilayer ETLs.