Aqueous-Solution Synthesized p-Type Cu 2 Se 0.96 Te 0.04- x I x /Cu 2 O Composite and Thermoelectric Performance of TEG Made of 6 Pairs of p-Leg Cu 2 Se 0.96 Te 0.02 I 0.02 /Cu 2 O Composite and n-Leg InSb 0.94 Bi 0.06 .

Cu 2 Se-based thermoelectric materials exhibit high dimensionless figure of merit ( zT ) values at elevated temperatures (900-1000 K) but relatively lower zT values at intermediate temperatures, approximately 500 K. We synthesized a series of polycrystalline Cu 2 Se 0.96 Te 0.04- x I x /Cu 2 O composites (where x = 0.00, 0.01, 0.02, and 0.03) using an energy-efficient synthesis method conducted at room temperature, followed by heat treatment at 923 K for 6 h. X-ray diffraction (XRD) analysis confirmed the monoclinic crystal structure of the α phase. The introduction of iodine doping at Te sites introduced electron carriers to p-type Cu 2 Se 0.96 Te 0.04 , reducing the hole carrier concentration. Consequently, the electrical resistivity increased, and the thermopower exhibited a significant increase. The incorporation of electron carriers into the p-type Cu 2 Se 0.96 Te 0.04 /Cu 2 O composites resulted in an enhanced power factor within the medium-temperature range. Specifically, at 500 K, the Cu 2 Se 0.96 Te 0.02 I 0.02 /Cu 2 O ( x = 0.02) composites demonstrated the highest power factor among the series of Cu 2 Se 0.96 Te 0.04- x I x /Cu 2 O composites, measuring 9.1 μW cm -1 K -2 . According to the weighted mobility analysis, it is clear that the x = 0.02 composite possesses the optimal carrier concentration, which accounts for its superior power factor compared to the other composites in the series. Furthermore, the Cu 2 Se 0.96 Te 0.02 I 0.02 /Cu 2 O composites and Cu 2 Se 0.96 Te 0.04 /Cu 2 O composites displayed zT values of 0.49 and 0.33, respectively, at 550 K. Additionally, iodine doping led to an enhancement in the average zT values between 450 and 550 K. Therefore, electron doping in p-type materials presents itself as a viable strategy for shifting the operating temperature of a thermoelectric device from high to medium temperature. We successfully fabricated a thermoelectric generator comprising 6 pairs of p-leg Cu 2 Se 0.96 Te 0.02 I 0.02 /Cu 2 O composites and n-leg InSb 0.94 Bi 0.06 . This TEG achieved impressive results, including a maximum output voltage, power output, power density, and efficiency of 0.115 V, 10.6 μW, 35.1 μW cm -2 , and 1.74% at a temperature difference (Δ T ) of 120 K.