Replacing toxic solvents with nonhazardous solvents is one of the key challenges for industrial scale commercialization of thin film perovskite photovoltaics. Here, nonhazardous solvent/alcohol/acid systems are presented for the single‐step deposition of pinhole‐free perovskite layers with combined lead halide precursors of Pb(CH3CO2)2·3H2O, PbCl2, and CH3NH3I. Comparable performance to standard hazardous inks is achieved: devices with 15.1% power conversion efficiency are demonstrated and maintain 13.5% tracked for 5 min at maximum power point. Blade coated 4 cm2 solar modules fabricated with highest performing device ink attain 11.9% in power conversion efficiency.

Concurrently pumped ultrasonic spray coating is implemented for rapid composition screening and in situ bandgap control of perovskite photovoltaics, achieving 15.7% efficiency for devices and 11.7% for modules, and tested under continuous maximum power point tracking.

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ABSTRACT:The TiO 2 layer made by electron beam (e-beam) induced evaporation is demonstrated as electron transport layer (ETL) in high efficiency planar junction perovskite solar cells. The temperature of the substrate and the thickness of the TiO 2 layer can be easily controlled with this e-beam induced evaporation method, which enables the usage of different types of substrates. Here, Perovskite solar cells based on CH 3 NH 3 PbI 3-x Cl x achieve power conversion efficiencies of 14.6% on glass and 13.5% on flexible plastic substrates. The relationship between the TiO 2 layer thickness and the perovskite morphology is studied with scanning electron microscope (SEM), atomic force microscope (AFM), and X-ray photoelectron spectroscopy (XPS). Our results indicate that pinholes in thin TiO 2 layer lead to pinholes in the perovskite layer. By optimizing the TiO 2 thickness, perovskite layers with substantially increased surface coverage and reduced pinhole areas are fabricated, increasing overall device performance.

wileyonlinelibrary.comTFPV is the use of toxic and halogenated solvents to dissolve the photoactive blend of materials. Furthermore, the deposition technique typically used for lab-scale solution-processed TFPV, spin coating, is not transferable to an industrial production setting. [4][5][6] Transitioning to nonhalogenated solvents affords a more environmentally friendly and less toxic approach, while blade coating offers a precise and reliable linear deposition technique that can be scaled from lab to fab. [7][8][9][10][11][12][13][14] Blade coating is a large area applicable, linear deposition technique used in rollto-roll and sheet-to-sheet coating industries. [ 4,[15][16][17] A blade, in near-contact with the underlying substrate, spreads a droplet of ink over a substrate, optimally resulting in a smooth and uniform coating, free of pinholes and ribbing. Blade height, blade speed, and substrate temperature are some of the key intrinsic deposition parameters, while ink composition is a determining factor for deposition results, solubility, and wettability.The Hansen solubility parameters (HSP) describe the properties of solutes, solvents, and solvent systems, and enable a theoretical description of the solubility of materials. [ 18,19 ] Three parameters represent the polar, hydrogen, and dispersion components of interaction for both materials and solvents, where similar-valued materials are more likely to dissolve each other than dissimilar-valued materials. The HSP space of solubility for a solute may be approximated by an ellipsoidal volume where solvent systems with a combined parameter value within this volume dissolve the solute, while those systems with a value outside the ellipsoid do not dissolve the solute. The HSP for a material are determined by measuring the material solubility in a variety of solvents with known solubility parameters and by fi tting an ellipsoid to the HSP for equal solute concentrations. Thus, the HSP are dependent on the threshold of solubility desired, shifting with the concentration limits of the foreseen application. This selection method has been described in several studies for the determination of solvents for organic photovoltaic materials. [ 7,12,20,21 ] Nonhalogenated solvents are one step toward industrially viable printing of solution-processed TFPV. [7][8][9][10][11][12][13][14] Several studies have reported potential replacements for halogenated solvents that are commonly used in OPV fabrication; however, With lab-scale solution-processed thin fi lm photovoltaic (TFPV) devices attaining market relevant effi ciencies, the demand for environmentally friendly and scalable deposition techniques is increasing. Replacing toxic halogenated solvents is a priority for the industrialization of solution-processed TFPV. In this work, a generalized fi ve-step process is presented for fabricating high-performance devices from nonhalogenated inks. Resulting from this process, several new solvent systems are introduced based on thiophene, tetralin, 1,2,4-trimethylbenzene, o -xylene...

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Space charge limited photocurrent is typically described as the limiting factor in carrier extraction efficiency for organic bulk heterojunctions with increasing thickness. It successfully characterizes the carrier extraction efficiency in these devices with thin to moderate thickness and dissimilar carrier mobilities. However, in this article we show that space charge limited photocurrent cannot solely explain the intensity dependent spectral response of extremely thick organic photovoltaics. In addition, interfacial depletion regions near the contacts contribute to the field distribution and carrier collection. Here, we describe charge collection efficiency with an optical p-i-n model, allowing for collection from band bending due to mobility-induced and interfacial-doping-induced space charge regions. We verify the model with up to 1400 nm thick spray-coated devices in both p-i-n (conventional) and n-i-p (inverted) architecture, including variations of thickness, illumination intensity, transport materials, and bifacial (semitransparent) devices.