Efficient hole‐transporting layer MoO₃:CuI deposited by co‐evaporation in organic photovoltaic cells

Abstract

In order to improve hole collection at the interface anode/electron donor in organic photovoltaic cells, it is necessary to insert a hole‐transporting layer. CuI was shown to be a very efficient hole‐transporting layer. However, its tendency to be quite rough tends to induce leakage currents and it is necessary to use a very slow deposition rate for CuI to avoid such negative effect. Herein, we show that the co‐deposition of MoO3 and CuI avoids this difficulty and allows deposition of a homogeneous efficient hole‐collecting layer at an acceptable deposition rate. Via an XPS study, we show that blending MoO3:CuI improves the hole collection efficiency through an increase of the gap state density. This increase is due to the formation of Mo5+ following interaction between MoO3 and CuI. Not only does the co‐evaporation process allow for decreasing significantly the deposition time of the hole‐transporting layer, but also it increases the efficiency of the device based on the planar heterojunction, CuPc/C60.

CuI-based hybrid junction in photovoltaic devices with semitransparent cathode

“…All experimental techniques were described earlier . A 3 nm thick MoO x layer was deposited on an ITO anode (substrate = polyethylene terephthalate, PET) to improve the hole transport . Then, CuI and C 60 layers were sequentially evaporated – Fig.…”

“…Cuprous iodide (CuI) is frequently used as a templating layer or a hole conductor in organic and perovskite‐based devices . However, its own conductive and optical properties are often neglected in favor of its application as an interfacial material.…”

“…In our previous work , we found out that n ‐ type fullerene C 60 and p‐type inorganic semiconductor CuI form a photovoltaic junction, which is transparent in most of the visible‐ and in the near infrared range. Devices incorporating such a heterojunction showed the open circuit voltage U oc of 0.4 V, providing an aluminum cathode is used in combination with Alq3 as an exciton blocking layer, EBL .…”

“…In the present study, we optimized the device scheme by substituting the EBL and introducing an ultrathin molybdenum oxide (MoO x ) anode buffer – Fig. .…”

Highly improved charge injection in pentacene-based organic transistors by chemically doping with copper iodide interlayer

“…Halide materials have a strong electron affinity that will lead to a great enhancement of hole injection such as ferric chloride (FeCl 3 ) and antimony pentachloride (SbCl 5 ) , etc. In particular, p‐type metal salts, such as copper iodide (CuI), do not only exhibit a high work function (∼5.4 eV) , but have a relatively low melting temperature (600 °C) than other metal oxides (800 °C for MoO 3 and 1490 °C for WO 3 ), which facilitates thermal evaporation . Thus, it has the unique potential to take advantage of both the suitable energy‐level alignment and the charge‐transfer complexes (CTC) formed in the pentacene/CuI doped region.…”