γ‐Valerolactone: A Nontoxic Green Solvent for Highly Stable Printed Mesoporous Perovskite Solar Cells

Abstract

Since their advent in 2009, lead halide perovskite solar cells (PSCs) have rapidly progressed to exhibit power conversion efficiencies (PCEs) of 25.5%, approaching that of commercially available monocrystalline silicon devices. [1][2][3][4] In addition to exhibiting excellent carrier mobility, high absorption coefficients, tunable bandgaps, and unusual defect tolerance, these semiconductors are cheap and amenable to low-cost solution-based processing. [5][6][7][8] To be considered commercially viable, stable, high-efficiency devices must be easily and reproducibly attainable at large scale for low-cost per watt peak. PSC commercialization is currently limited by poor device stability under operating conditions; perovskites are particularly sensitive to humidity as well as exhibiting UV, thermal, and oxygen sensitivity in many architectures. [9][10][11][12] In addition, many device architectures use prohibitively expensive or toxic components or manufacturing methods inherently unsuitable for large-scale production. Expensive and unstable organic hole extraction materials (HTMs) such as spiro-OMeTAD are particularly problematic. This has led to significant research on alternative materials such as NiO and work on hole conductor free carbon-based devices with improved operational stability. [13][14][15][16] Mesoscopic carbon-based perovskite solar cells (CPSCs) make use of easily scaled manufacturing processes and are frequently described as one of the frontrunners for perovskite commercialization. Fabricated via sequential screen printing of mesoporous TiO 2 , ZrO 2 , and carbon before drop casting of the perovskite precursor, CPSCs are highly stable, benefitting from both the lack of a hole transporter and the presence of a >20 μm-thick, encompassing mesoporous scaffold, which provides mechanical stability and limits oxygen and moisture access. [17] Performance and stability are further enhanced by incorporating 5-aminovaleric acid (AVAI) to improve precursor infiltration, induce highly stable 2D/3D crystal formations at the perovskiteÀTiO 2 interface, and limit superoxide production. [17,18] Polyurethane/glassencapsulated devices produced using AVA (x) MA (1Àx) PbI 3 γ-butyrolactone (GBL) perovskite precursors recently passed stringent IEC61215:2016 tests, including damp heat tests (85 C at 85% relative humidity (RH), for 1100 h), thermal cycling tests (À40 to 85 C for 200 cycles), UV preconditioning tests (60 C, 50 kWh m À2 ), and maximum power point testing light-soaking tests (55 C, 9000 h). [19] This impressive stability combined with the use of scalable deposition techniques make CPSCs attractive for commercial development, and manufacturing bottlenecks are already being addressed in the scientific literature, for example, using nearinfrared annealing and robotic infiltration methods to drastically reduce heating times and automate infiltration. [18,20,21] However, significant barriers to commercial application still exist. [22,23] For example, the most common precursor solvents for CPSCs, dimethylformamide...

Strategies towards Cost Reduction in the Manufacture of Printable Perovskite Solar Modules

“…In the two-step (sequential) method, a solution of lead iodide (PbI 2 ) in DMF is drop-casted onto the carbon layer, and after drying and solvent evaporation, the stack is immersed into a solution of methylammonium iodide (MAI) in isopropyl alcohol (IPA) for a couple of minutes to form the perovskite. In the one-step deposition method, both perovskite infiltration and conversion take place in one step, using a mixture of PbI 2 and MAI in an organic solvent such as gamma-butyrolactone (GBL), dimethyl sulfoxide (DMSO), a mixture of DMSO and dimethylformamide (DMF) and, n-methyl-2-pyrrolidone (NMP) [29][30][31][32]. The choice of one-step or two-step perovskite deposition method affects the properties of the perovskite layer.…”

One-pot synthesis of novel ligand-free tin(ii)-based hybrid metal halide perovskite quantum dots with high anti-water stability for solution-processed UVC photodetectors

“…1,2,4,5,[9][10][11][12][13][14] However, toxic Pb has caused serious concern due to its environmental impact, and the toxic mixture of dimethyl formamide (DMF) and dimethyl sulfoxide (DMSO) can also harm human health and the environment seriously. 15 In order to eliminate the toxicity of Pb from the environment, Pb 2+ can be replaced by lower-toxicity cations, such as Sn 2+ , Ge 2+ , Bi 3+ or Sb 3+ . However, the trivalent oxidation state of Sb 3+ and Bi 3+ destroys the electrically neutral equilibrium in ABX 3 .…”

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

“…For the case of MAPbI 3 -based perovskite, several studies have utilized solvents and solvent mixtures that reduce or eliminate the use or generation of substances hazardous to humans, animals, plants, and the environment, also referred to as green solvents, aiming to demonstrate alternatives to DMF. − However, regarding multi-cation perovskite thin films, reports particularly concerning blade coating describe, to the best of our knowledge, merely the utilization of toxic solvent systems. ,,− More nonconventional solvents and co-solvents used for upscaling PSCs are acetonitrile (ACN), ,,, 2-methoxyethanol (2-ME), ,,,− or 2-methylpyrazine (2-MP), but it is up for debate if these solvents are sufficiently green …”