One-Step Blade Coating of Inverted Double-Cation Perovskite Solar Cells from a Green Precursor Solvent

Abstract

Perovskite solar cells (PSCs) have recently gained power conversion efficiencies (PCEs) of up to 25.5% on lab-scale nearly exclusively processed from precursor solutions involving harmful and polluting solvents like dimethylformamide (DMF). However, solution processing of green and environmentally safe solvents such as dimethyl sulfoxide (DMSO) via scalable printing is 2 challenging mainly caused by two reasons: firstly pronounced precursor solution dewetting on the subjacent layer and secondly its complex quenching process. In this work, we report on one-step blade coating of inverted (p-i-n) double-cation PSCs using solely DMSO at low processing temperatures. To avoid dewetting of the DMSO-based solution on the hydrophobic hole transport layer (HTL) and to realize adequate quenching, a blade coated wetting agent of silicon oxide nanoparticles at the HTL/perovskite interface and gas stream-assisted drying is applied, respectively. Trends in absorber grain size, morphology, crystallinity and elemental composition of samples from both toxic and green solvent concepts are compared revealing analogous findings.Consequently, PSCs blade coated from DMSO achieve PCEs of up to 16.7% on a 0.24 cm 2 active area comparable to the ones from a DMF:DMSO mixture (16.9%) and thus demonstrating that using toxic DMF is unnecessary. This represents an important step for bringing PSCs solution processed from environmentally friendly precursor solvents closer to industrial implementation.

Drying and Coating of Perovskite Thin Films: How to Control the Thin Film Morphology in Scalable Dynamic Coating Systems

“…For controlling the crystallization step, the drying film needs to rapidly transit into a supersaturation state by fast extraction of solvents , a process called “quenching”. There are different variants of quenching: rinsing the solution film with an antisolvent, exposing the film to vacuum, depositing the film on a pre-heated substrate, − rapidly annealing the film by infrared radiation, or inducing fast drying by increased convection over the substrate − (often referred to as “gas quenching”). Although very often applied in record laboratory-scale spin-coated devices, the antisolvent quenching is not facile to up-scale because the rinsing with the antisolvent must occur at exactly the right time and flow rate .…”

All-blade-coated flexible perovskite solar cells & modules processed in air from a sustainable dimethyl sulfoxide (DMSO)-based solvent system

“…LP is a naturally occurring amphoteric zwitterionic surfactant derived from egg yolk, used as an additive in the single-step blade coating of the perovskite layer to reduce surface tension and passivate charge traps. 36,[58][59][60][61] We investigated the effect of this additive in two-step blade coating of the perovskite for the rst time by adding this surfactant to the PbI 2 -(FAI) 0.3 -(CsI) 0.15 ink. The morphology of the PbI 2 -(FAI) 0.3 -(CsI) 0.15 lm remained unchanged upon addition of the LP as shown in Fig.…”

“…34 DMSO has the highest DN among these solvents, and it can dissolve PbI 2 in the presence of different halide salts and can be used to deposit compositions of MA-based, FA-based, Cs-based, and mixed cation perovskite. 35,36 DMSO is mainly used as a cosolvent in perovskite deposition and the development of efficient PSCs based on DMSO is encouraged. 37 However, DMSO is a nonvolatile solvent with a high boiling point (189 °C) and a low vapor pressure (0.6 mm Hg at 25 °C).…”

“…Previous studies on single-step deposition of DMSO-based perovskite solution using the blade coating technique required high substrate temperature (150 °C) or high annealing temperature (170 °C). 36,42 In addition, the previously reported devices were fabricated under a nitrogen atmosphere. With the help of additive engineering and optimized drying of the wet lm with high-ow gas quenching, we obtained a smooth lm of Cs 0.15 FA 0.85 PbI 3−x Br x perovskite on a large coating area (94 cm 2 ).…”

Green-solvent-processed formamidinium-based perovskite solar cells with uniform grain growth and strengthened interfacial contact via a nanostructured tin oxide layer

“…To overcome the solubility issue, dimethyl sulfoxide (DMSO) with a high donor number and high coordination ability is used as the green solvent for the perovskite precursor. [17][18][19] Nevertheless, owing to its non-volatility, DMSO failed to achieve a pinhole-free morphology with high crystallinity in perovskite films when used alone as a processing solvent. 20 Besides DMSO, 2-methoxyethanol (2-Me) with lower toxicity was also used to replace DMF in many large-area fabrication processes of PSCs.…”