Hydrothermally Treated SnO₂ as the Electron Transport Layer in High‐Efficiency Flexible Perovskite Solar Cells with a Certificated Efficiency of 17.3%

Abstract

Perovskite solar cells (PSCs) are one of the most promising solar energy conversion technologies owing to their rapidly developing power conversion efficiency (PCE). Low-temperature solution processing of the perovskite layer enables the fabrication of flexible devices. However, their application has been greatly hindered due to the lack of strategies to fabricate high-quality electron transport layers (ETLs) at the low temperatures (≈100 °C) that most flexible plastic substrates can withstand, leading to poor performances for flexible PSCs. In this work, through combining the spin-coating process with a hydrothermal treatment method, ligand-free and highly crystalline SnO 2 ETLs are successfully fabricated at low temperature. The flexible PSCs based on this SnO 2 ETL exhibit an excellent PCE of 18.1% (certified 17.3%). The flexible PSCs maintained 85% of the initial PCE after 1000 bending cycles and over 90% of the initial PCE after being stored in ambient air for 30 days without encapsulation. The investigation reveals that hydrothermal treatment not only promotes the complete removal of organic surfactants coated onto the surface of the SnO 2 nanoparticles by hot water vapor but also enhances crystallization through the high vapor pressure of water, leading to the formation of high-quality SnO 2 ETLs.

Recent Advances of Device Components toward Efficient Flexible Perovskite Solar Cells

“…Recently, it was reported that adding cesium (Cs) at the cation site can significantly reduce fabrication temperature for perovskite films . Due to the abundance of the precursor components and ease of fabrication, a variety of low‐temperature techniques has been developed to promote the performance of the PSCs in the past few years.…”

“…The resulted FPSCs exhibited a PCE of 18.1% and maintained 85% of the initial PCEs after 1000 bending cycles. In addition, the device held impressive stability that maintained over 90% of the initial PCE after a 30‐day storage in ambient air with no encapsulation . Fan and coworkers prepared SnO 2 ETLs with a room‐temperature sputtering process .…”

“…a) Schematic of SnO 2 ETL fabrication through a thermal annealing or hydrothermally treating process. Reproduced with permission . Copyright 2019, Wiley‐VCH.…”

“…[96] Recently, it was reported that adding cesium (Cs) at the cation site can significantly reduce fabrication temperature for perovskite films. [82,[97][98][99][100] Due to the abundance of the precursor components and ease of fabrication, a variety of low-temperature techniques has been developed to promote the performance of the PSCs in the past few years. Typical procedures include one-step ( Figure 3a) [102,[104][105][106][107] and two-step sequential solution deposition ( Figure 3b) [108][109][110][111][112] and vapor-assisted solution process (VASP) ( Figure 3c).…”

“…In addition, the device held impressive stability that maintained over 90% of the initial PCE after a 30-day storage in ambient air with no encapsulation. [99] Fan and coworkers prepared SnO 2 ETLs with a room-temperature sputtering process. [193] .…”