Thermally Stable Solution Processed Vanadium Oxide as a Hole Extraction Layer in Organic Solar Cells

Abstract

Low-temperature solution-processable vanadium oxide (V2Ox) thin films have been employed as hole extraction layers (HELs) in polymer bulk heterojunction solar cells. V2Ox films were fabricated in air by spin-coating vanadium(V) oxytriisopropoxide (s-V2Ox) at room temperature without the need for further thermal annealing. The deposited vanadium(V) oxytriisopropoxide film undergoes hydrolysis in air, converting to V2Ox with optical and electronic properties comparable to vacuum-deposited V2O5. When s-V2Ox thin films were annealed in air at temperatures of 100 °C and 200 °C, OPV devices showed similar results with good thermal stability and better light transparency. Annealing at 300 °C and 400 °C resulted in a power conversion efficiency (PCE) of 5% with a decrement approximately 15% lower than that of unannealed films; this is due to the relative decrease in the shunt resistance (Rsh) and an increase in the series resistance (Rs) related to changes in the oxidation state of vanadium.

Robust Inorganic Hole Transport Materials for Organic and Perovskite Solar Cells: Insights into Materials Electronic Properties and Device Performance

“…As already mentioned, low‐temperature synthesis and deposition methods under ambient conditions for OSCs using TMOs are highly desirable. Alsumani et al [ 185 ] included V 2 O x interlayers (acquired from a vanadium oxytriisopropoxide precursor) in OSCs and investigated their performance characteristics at different annealing temperatures. Figure shows the energy levels of the materials used in this study, including the HOMO and LUMO levels, along with the chemical structure of the active layers.…”

Aqueous Solution‐Processed Vanadium Oxide for Efficient Hole Injection Interfacial Layer in Organic Light‐Emitting Diode

“…It is reported that sol-gel derived VO x interfacial layer does not require any post-annealing or plasma treatment, which significantly simplifies device fabrication process. [1,8,12,22] VO x also possesses high work function of 4.7-7.2 eV depending on processing conditions. [23] In addition to regularly used thermal evaporation V 2 O 5 as interfacial modification, [24,25] solution-processed VO x draws more and more attentions in OLEDs, [11,23,26] polymer LEDs, [10,22] and organic solar cells.…”

“…[23] In addition to regularly used thermal evaporation V 2 O 5 as interfacial modification, [24,25] solution-processed VO x draws more and more attentions in OLEDs, [11,23,26] polymer LEDs, [10,22] and organic solar cells. [1,8,[12][13][14][15] Rather than producing solutionprocessed VO x from ammonia solution, [13] isopropanol solution [1,8,10,12,14,16] or sodium metavanadate solution, [15] VO x aqueous solution has seen a tremendous increase in research interest. It is documented that V 2 O 5 powders showing small amounts of solubility in water, [9,27] which provides an easy-to-do method of preparing VO x aqueous solution.…”

“…In recent years, solution‐processed techniques with low cost and high‐throughput production boost developing novel solution‐processed HILs such as poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) and graphene oxide, as well as solubilizing conventional HILs. Solution‐processed transition metal oxides of MoO x , VO x , WO 3 , La 2 O 3 , and NiO feature high chemical/thermal stability and exceptional electronic properties, making them the favorite interfacial layers in organic electronic devices.…”

“…Solution‐processed VO x is widely recorded for energy alignment in organic electronic device. It is reported that sol‐gel derived VO x interfacial layer does not require any post‐annealing or plasma treatment, which significantly simplifies device fabrication process . VO x also possesses high work function of 4.7–7.2 eV depending on processing conditions .…”