Cuprous iodide - a p-type transparent semiconductor: history and novel applications

Abstract

Halide semiconductors stand at the very beginning of semiconductor science and technology. CuI was reported as the first transparent conductor, and the first field effect transistor was made from KBr. Although halogens are frequently used in semiconductor preparation, little use is currently made from halide semiconductors in electronics and photonics. We review past reports on the metal halide semiconductor CuI and related alloys and discuss recent progress with regard to this material including its use in organic electronics and solar cells as well as our own work on fully transparent bipolar heterostructure diodes (p‐CuI/n‐ZnO) with high rectification of several 107 and ideality factors down to 1.5. γ‐CuI(111) thin film on glass (1 × 1 cm2) and IV‐characteristics of p‐CuI/n‐ZnO/a‐Al2O3 bipolar heterojunction diode.

CuI Film Produced by Chemical Extraction Method in Different Media

“…The quality of the films that we have produced on amorphous glass through a simple, easy and cheap method is similar to the quality of the ones that Kosta et al have produced through electrochemical method on a crystalline structure; a similar type of surface can be seen in Figure 7a. Grundman et al, who showed that they have produced the most regular structure through SEM images, have captured particle structures similar to triangular prism, as can be seen in our SEM images 19 . Bu all these researchers have attempted to growth crystalline film on crystal substrates using devices.…”

Room-temperature synthesized copper iodide thin film as degenerate p-type transparent conductor with a boosted figure of merit

“…Considering the fact that the obtained CuI films are in the polycrystalline state, further improvement in the hole , other p-type (black circles), and n-type TCs (blue squares). P-type TCs: SrCrO (19), CuCrMgO (18), CaCoO (46), CuScO (10), LaSrCrO (19), CuYCaO (11), ZnRhO (47), AgCoO (45), MgGaN (6,43), MgCrO (48), CuAlO (44), SrCuO (12), CuGaO (8), ZnON (49), iodi-CuI (prepared by iodization) (36), sput-CuI (prepared by sputtering) (29), evap-CuI (prepared by thermal evaporation) (27), and PLD-CuI (prepared by PLD) (28). The superscripts of p-type TCs indicate the FOM.…”

“…However, the performance of CuI as a highly conducting p-type TC has not been well explored, because it is commonly recognized as a nondegenerate semiconductor with a roomtemperature conductivity limited to values below 100 S/cm (27). In contrast, conventional n-type TCs are usually degenerate semiconductors, such as indium tin oxide, which act as metallic conductors with conductivity above 10 3 S/cm.…”

“…On the other hand, CuI does not require high synthesis temperatures like other p-type TCs. The stable cubic structure makes it easy to synthesize CuI thin films near room temperature using a number of chemical and physical methods, including vapor iodization (20), thermal evaporation (27), pulsed laser deposition (PLD) (28), and sputtering (29)(30)(31). Therefore, CuI is readily compatible in organic electronics, for example as (part of) the electrode in organic light-emitting diodes and organic solar cells (32)(33)(34).…”

Truly Transparent p-Type γ-CuI Thin Films with High Hole Mobility

“…The most common route is the chemical reaction of Cu thin films with vapor-phase iodine (known as the vapor iodination method), 8,21,[24][25][26] a Cu film is quickly converted to a polycrystalline γ-CuI film upon exposure to iodine vapor. The resulting polycrystalline γ-CuI films exhibit semiconducting properties, with hole densities of 10 18 -10 19 cm -3 and hole mobilities of 1-10 cm 2 V -1 s -1 .…”