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...
