Vapor Phase Infiltration Improves Thermal Stability of Organic Layers in Perovskite Solar Cells

Despite the rapid increase in power conversion efficiency (PCE) of perovskite solar cells (PSCs) over the past decade, stability remains a major roadblock to commercialization. This work shows vapor phase infiltration (VPI) as a tool to create hybrid organic-inorganic layers that improve the stability of organic charge transport layers, such as hole -selective spiro-OMeTAD in PSCs and in other organic electronic devices. Using X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and grazing incident wide-angle X-ray scattering (GIWAXS), we identify that infiltration of TiOx via VPI hinders the crystallization of the spiro-OMeTAD layer by likely preventing the N-N stacking of the molecules. Infiltrated PSCs retained more than 80% of their original efficiency after an operando stability test of 200 h at 75 degrees C, double the efficiency retained by devices without infiltration, in which the efficiency rapidly decreases in the first 50 h. This work provides a blueprint for using VPI to stabilize organic charge transport layers via prevention of N-N stacking leading to deleterious crystallization that shortens device lifetimes.

Automated summary

This study demonstrates the use of vapor phase infiltration (VPI) to create hybrid organic-inorganic layers, improving the stability of organic charge transport layers in perovskite solar cells (PSCs). By infiltrating TiOx via VPI, the crystallization of the spiro-OMeTAD layer is hindered, preventing N-N stacking of the molecules. The infiltrated PSCs retained over 80% of their original efficiency after a 200-hour stability test at 75 degrees C, while devices without infiltration rapidly decreased in efficiency within the first 50 hours. This work provides a blueprint for stabilizing organic charge transport layers using VPI and preventing deleterious crystallization that shortens device lifetimes.