Molecule‐Assisted Chemical Bath Deposition of Tin Oxide Electron Transport Layers in Perovskite Solar Cells

Abstract

Chemical bath deposition (CBD) is a widely used approach to deposit the tin oxide (SnO2) electron transport layer (ETL) in the perovskite solar cell (PSC). However, the defect states in the CBD‐resulted SnO2 ETLs limit the electron extraction/transport from the perovskite to the ETL and lead to poor PSC performance. Herein, ethylenediaminetetraacetic acid dipotassium (EDTA‐2K) is used as an additive in the CBD precursor of the SnO2 ETL, which results in the chelation of Sn2+ and EDTA during the hydrolysis process. This strategy decreases the concentration of free Sn2+ in the precursor for hydrolysis and slows down the CBD process, thus attributes to the decreased surface defect states as well as the enhanced conductivity of the ETL. As a result, the EDTA‐2K additive makes the CBD SnO2 ETL with efficient electron extraction and transporting capability. The champion device achieves a power conversion efficiency (PCE) of 21.87%, which is significantly higher than that of the pristine CBD SnO2‐based device (20.25%). In addition, the device with an active area of 1.21 cm2 achieves a high PCE of 19.23%. This strategy makes the CBD SnO2 an excellent ETL candidate for the development of low‐cost and large‐scale PSCs.

Dopamine Sulfonate Ligand-Assisted TiO2 Deposition Enabling Highly Efficient and Stable Perovskite Solar Cells

“…In particular, mesoporous-structure devices based on the TiO 2 scaffold are dominant in the efficiency competition in PSCs, with certified PCE jumping from 14.1% in 2013 to 25.5% in 2021 . Unfortunately, the fabrication of mesoporous-TiO 2 requires high-temperature sintering (450–550 °C) to improve crystallinity and carrier mobility, which restricts its application in flexible and tandem PSCs. , Alternatively, planar PSCs with low-temperature processing (<150 °C) open many possibilities for plastic conductive substrates and device structures choice and have been intensively researched, especially for the ETL material, such as compact-TiO 2 , SnO 2 , and ZnO. − Among them, devices based on SnO 2 with PCE over 25% have emerged one after another and are expected to achieve a higher record efficiency breakthrough through modification of ETL materials, yet the low-cost, reserved-abundant TiO 2 has more prominent advantages for commercialization and large-scale production of PSCs . However, it was claimed that the low-temperature deposited compact-TiO 2 ETLs have low electron mobility and poor film quality, resulting in excessive charge carrier accumulation, severe nonradiative recombination losses, and inferior long-term stability of PSCs.…”