Facile NiOx Sol-Gel Synthesis Depending on Chain Length of Various Solvents without Catalyst for Efficient Hole Charge Transfer in Perovskite Solar Cells

Abstract

Nickel oxide (NiOx)–based perovskite solar cells (PSCs) have recently gained considerable interest, and exhibit above 20% photovoltaic efficiency. However, the reported syntheses of NiOx sol-gel used toxic chemicals for the catalysts during synthesis, which resulted in a high-temperature annealing requirement to remove the organic catalysts (ligands). Herein, we report a facile “NiOx sol-gel depending on the chain length of various solvents” method that eschews toxic catalysts, to confirm the effect of different types of organic solvents on NiOx synthesis. The optimized conditions of the method resulted in better morphology and an increase in the crystallinity of the perovskite layer. Furthermore, the use of the optimized organic solvent improved the absorbance of the photoactive layer in the PSC device. To compare the electrical properties, a PSC was prepared with a p-i-n structure, and the optimized divalent alcohol-based NiOx as the hole transport layer. This improved the charge transport compared with that for the typical 1,2-ethanediol (ethylene glycol) used in earlier studies. Finally, the optimized solvent-based NiOx enhanced device performance by increasing the short-circuit current density (Jsc), open-circuit voltage (Voc), and fill factor (FF), compared with those of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)–based devices.

PEG-assisted Sol-gel Synthesis of Compact Nickel Oxide Hole-Selective Layer with Modified Interfacial Properties for Organic Solar Cells

“…The average PCE, V oc , and FF values were 6.91%, 0.722 V, and 66.98% for OPVs with c-NiO/FTO and 5.68%, 0.696 V, and 52.10% for OPVs with NiO/FTO, respectively. These enhancements in V oc and FF can be attributed to the modified interfacial properties from the uniform and smooth morphology of the compact NiO interlayer, because these parameters were strongly affected by the contact resistances at the interface and the leakage currents in the metal oxide interlayers [33,34]. However, the tiny pinholes in c-NiO/FTO could not fully suppress the charge recombination, resulting in the slight improvement of the J sc value from 14.06 mA/cm 2 for NiO/FTO to 14.28 mA/cm 2 for c-NiO/FTO.…”

Investigating the Growth of CH3NH3PbI3 Thin Films on RF‐Sputtered NiOx for Inverted Planar Perovskite Solar Cells: Effect of CH3NH3+ Halide Additives versus CH3NH3+ Halide Vapor Annealing

“…And, the sp‐NiO x HTL‐based PSCs show highly stable and operational output up to 4500 h . However, the performance of sp‐NiO x ‐based PSCs is not as high as solution processed ones . This low PCE of the sp‐NiO x is associated with greater loss in photovoltage and their open circuit voltage ( V oc ) is especially ≈100 mV lower than that of the solution processed NiO x ‐based PSCs .…”

“…Nickel oxide (NiO x ) is a promising hole transport layer (HTL) that is employed in PSCs compared to widely used spiro‐OMeTAD because of its high optical transparency, high stability, easy processability, and wide bandgap (crucial for aiding as effective electron blocking layer) . Vapor deposition of NiO x such as sputtering or evaporating is feasible for mass production and is one of the viable methods to deposit conformal pinhole‐free layer and the deposition parameters can be precisely controlled .…”

“…Vapor deposition of NiO x such as sputtering or evaporating is feasible for mass production and is one of the viable methods to deposit conformal pinhole‐free layer and the deposition parameters can be precisely controlled . The combination of phenyl‐C61‐butyric acid methyl ester (PCBM) and the radio frequency (RF)‐sputtered NiO x (sp‐NiO x ) as electron transport layer (ETL) and HTL, respectively, for indium tin oxide(ITO)/sp‐NiO x /MAPbI 3 perovskite (MA + = CH 3 NH 3 + )/PCBM/aluminium‐doped zinc oxide (AZO)/Ag as p‐i‐n (inverted) architecture demonstrated high stability against air and heat stress with hysteresis‐free characteristics . And, the sp‐NiO x HTL‐based PSCs show highly stable and operational output up to 4500 h .…”

“…[7,8] Nickel oxide (NiO x ) is a promising hole transport layer (HTL) that is employed in PSCs compared to widely used spiro-OMeTAD because of its high optical transparency, high stability, easy processability, and wide bandgap (crucial for aiding as effective electron blocking layer). [9][10][11][12][13][14][15][16][17][18][19] Vapor deposition of NiO x such as sputtering or evaporating is feasible for mass production and is one of the viable methods to deposit conformal pinholefree layer and the deposition parameters can be precisely controlled. [10][11][12][13] The combination of phenyl-C61-butyric acid methyl ester (PCBM) and the radio frequency (RF)-sputtered NiO x (sp-NiO x ) as electron transport layer (ETL) and HTL, respectively, for indium tin oxide(ITO)/sp-NiO x /MAPbI 3 perovskite (MA + = CH 3 NH 3…”