Inverted Organic Solar Cells with Sol–Gel Processed High Work‐Function Vanadium Oxide Hole‐Extraction Layers

Abstract

For large‐scale and high‐throughput production of organic solar cells (OSCs), liquid processing of the functional layers is desired. We demonstrate inverted bulk‐heterojunction organic solar cells (OSCs) with a sol–gel derived V2O5 hole‐extraction‐layer on top of the active organic layer. The V2O5 layers are prepared in ambient air using Vanadium(V)‐oxitriisopropoxide as precursor. Without any post‐annealing or plasma treatment, a high work function of the V2O5 layers is confirmed by both Kelvin probe analysis and ultraviolet photoelectron spectroscopy (UPS). Using UPS and inverse photoelectron spectroscopy (IPES), we show that the electronic structure of the solution processed V2O5 layers is similar to that of thermally evaporated V2O5 layers which have been exposed to ambient air. Optimization of the sol gel process leads to inverted OSCs with solution based V2O5 layers that show power conversion efficiencies similar to that of control devices with V2O5 layers prepared in high‐vacuum.

Transition metal oxides as hole-selective contacts in silicon heterojunctions solar cells

“…For V 2 O 5 , the V2p core level was decomposed into two doublet peaks centered at 518.1 and 516.5 eV binding energies, with a doublet spin-orbit splitting Δ BE = 7.6 eV and a peak area ratio of 2:1. These characteristic binding energies are attributed to the presence of both V +5 and V +4 cations [28], as shown in Fig. 2 and Mo +5 respectively [29] as shown in Fig.…”

“…Nonetheless, the absence of the W +5 oxidation state on the air-exposed surface could be caused by tungsten reoxidation by air, not excluding oxygen vacancies from the material bulk. The characteristic defect states that lie within the band gap of these non-stoichiometric TMOs were also identified near the Fermi level [28,29,30], although in a minor degree for WO x (Fig. 2(d)).…”

Recent Advances in Nanostructured Vanadium Oxides and Composites for Energy Conversion

“…[232] Isopropanol and vanadium(V) oxitriisopropoxide solution was used to prepared 10-to 45-nm-thick V 2 O 5 layers via hydrolysis at ambient condition without any post-treatments (Figure 17a). [233] The work function (WF) of 5.6 eV was achieved, and shown even better characteristics than PEDOT:PSS (Figure 17b).…”

Metal oxide semiconducting interfacial layers for photovoltaic and photocatalytic applications

“…In comparison with MoO 3 , research on V 2 O 5 is rudimentary. For a better understanding of the charge transport mechanism at the V 2 O 5 -polymer interface, additional investigations of the interface electronic structures are indispensable [43,104,105]. The inverted OSC devices fabricated with PCDTBT in the active layer along with TiO 2 as the electron transport layer (ETL) and MoO 3 as the hole transfer layer (HTL) exhibits high Voc of about 91 % with a PCE of 7.2 % as shown in Table 1, owing to low band gap of the polymer and efficient charge transport across the interface [98].…”