Structural Modifications and Enhanced Thermoelectric Performance of CuI Nanoparticles Induced via Al‐Doping

Abstract

highly efficient TE materials that possess a high electrical conductivity (σ), large Seebeck coefficient (S), and low thermal conductivity (κ) is very important. The values of these TE properties are ultimately affecting the value of the dimensionless parameter figure of merit ZT, which evaluates the efficiency of TE materials, and it is expressed as S 2 σT/κ, where T is the absolute temperature. [1] In the last 7-8 decades many materials have been developed and tested for the TE efficiency. In the 1950s, Bi 2 Te 3 was emerged as a promising inorganic TE material, [2] n-type Bi 2 Te 3-x Se x and p-type Bi 2-x Sb x Te 3 [3] were further found to show higher TE performance. Since then, a wide variety of materials, such as oxides, sulfides, silicides, selenides, skutterudites, intermetallic compounds, organic polymers, etc., have been proposed and investigated for TE applications. [4][5][6][7][8][9] Nanocarbon materials and their composites are also studied extensively in recent years. [10][11][12] Most of these materials, however, still demonstrate low TE efficiency at low temperature range of 200-400 K.A limited number of TE materials such as Cu 2 Se, [13] Ag 2 Se, [14] Bi 2 Te 3 nanostructures, [15,16] and Bi 0.5 Sb 1.5 Te 3 /PEDOT:PSS composite, [17] have been developed to be used near the room temperature (RT). Another work was also continued to develop TE materials with high ZT such as Mg 3 Sb 2 -based, which exhibits ZT near 1. [18] Although, these efforts were performed mainly for developing TE materials at RT, evolving more TE materials at RT are still in the early stages. Many reports have recently identified that copper iodide (CuI) is a promising material, which demonstrates good TE performance near RT. [19][20][21][22][23][24] The gamma phase (zinc blende structure) of CuI (denoted as γ-CuI) has a wide band gap (3.1 eV) with electron holes as charge carriers and it is classified as a flexible transparent p-type semiconductor. CuI is an environmentally friendly material due to its nontoxicity and naturally abundant elements, id est copper and iodine. In this material, iodine is a heavy element which leads to reduce the thermal conductivity and therefore enhances TE efficiency. The γ-CuI has been investigated for several applications, such as transparent electrode for solar cells, RT blue-emitting devices, vacuum fluorescent, and field emission displays. [19] Many researches have produced CuI in different forms including nanoparticles (NPs) and evaluated them for TE applications. [19][20][21][22][23][24] Recently, the effect of doping CuI NPs with several activators to enhance the TE performance has been reported. Some of the activators such as terbium (Tb) and iron (Fe) Thermoelectric (TE) materials are of great importance for harvesting thermal energy from waste or solar heat. One of the promising TE materials is copper iodide (CuI), which is nontoxic, earth-abundant, and has a high Seebeck coefficient at room temperature (RT). The TE performance of CuI nanoparticles (NPs) is found to be further enhance...

Solution-processed copper(i) iodide via co-doping for enhanced hole selective contacts in p-type crystalline silicon solar cells

“…In an iodine-rich environment, the presence of excess iodine could facilitate the substitution of Cu + sites by the Al 3+ in the crystal lattice. 41 As a result, a much higher concentration of V Cu is generated, which dominates the recombination path as observed in the PL spectra.…”

“…This behavior could be ascribed to the induced lattice distortions caused by the difference in ionic radius between Cu + and Al 3+ ions. 40,41 Note that the Al 2p peak of the XPS spectra is clearly observed, indicating the successful incorporation of Al 3+ into the film (Fig. S6, ESI †).…”

Evolution of Thermoelectric Generators: From Application to Hybridization

“…TEGs are difficult to obtain significant temperature gradients in practical applications for the limitations of temperature resistance properties of flexible materials and application scenarios. [296][297][298][299][300][301][302][303][304][305][306][307][308][309][310][311][312][313][314][315] Accordingly, the previous section suggests that flexible TEGs at smaller temperature gradients are capable of capturing the vertical temperature gradient between the hot and cold ends by optimizing the design structure to provide high power density. Moreover, more stacking of thermoelectric legs per unit area is achieved by optimizing the design.…”