## 1 Introduction  
Humans need to care for our \"mother earth\" with intelligence, diligence, and heart. In a society experiencing an energy shortage, the pursuit of sustainable development has become the social mainstream. With rapid economic development, industrial scale expands. However, energy and environmental problems gradually appear at the same time. In the process of industrial production, most energy is released in the form of heat. Thermoelectric (TE) materials can directly convert waste heat into electricity based on the Seebeck effect [1; 2]. While TE materials show a great prospect environmentally and economically, the lower efficiency of TE materials limits their wide application. The efficiency of TE materials is determined by the dimensionless figure of merit \(ZT\), which is defined as \(ZT=\alpha^{2}\sigma\Gamma/\kappa\), where \(\alpha\) is Seebeck coefficient, \(\sigma\) is electrical conductivity, \(\kappa\) is the thermal conductivity, and T is absolute temperature. A good TE material should have high \(\alpha\) and \(\sigma\) as well as low \(\kappa\) value. The intrinsic properties of TE materials determine the coupling effect between the conductivity and Seebeck coefficient. Generally, the higher power factor (PF = \(\alpha^{2}\sigma\)) corresponds to higher power output. PF is proportional to the effect mass (\(m^{*}\)) and mobility of the carriers (\(\mu\)). Thermal property is determined by the total thermal conductivity (\(\kappa\)), which is composed of lattice part (\(\kappa_{\rm L}\)) and carrier part (\(\kappa_{e}\)). Electronic thermal conductivity (\(\kappa_{e}\)) is proportional to the conductivity. Reducing the \(\kappa_{\rm L}\) of a TE material is an effective way to reduce the total thermal conductivity. Cu\({}_{2}\)SnSe\({}_{3}\) with a diamond structure has gained great attention recently due to its low thermal conductivity originating from the complex crystal structure and high specific heat. In addition, Cu\({}_{2}\)SnSe\({}_{3}\) has good electrical conductivity and adjustable electrical properties [3]. To further improve the thermoelectric properties of Cu\({}_{2}\)SnSe\({}_{3}\), a great deal of research has been carried out to optimize the material from multiple perspectives. [PERSON] et al. obtained a maximum \(ZT\) of 0.45 for Cu\({}_{2}\)SnSe\({}_{3}\) material at 773 K by one-step high-pressure combustion synthesis (HPCS) [4]. [PERSON] et al. prepared the Cu\({}_{2}\)SnSe\({}_{3}\) material using combustion synthesis and obtained a maximum \(ZT\) of 0.51 at 773 K, which is the best result for Cu\({}_{2}\)SnSe\({}_{3}\) compared to other methods [5]. [PERSON] et al. optimized the synthesis parameters to form uniform particles of wurtzite, cubic, linear heterostructures, and tetrapods by colloidal synthesis. The facile synthesis strategy opens pathways for extension to other compositions of multielement copper chalcogenides where the cubic and hexagonal phases can be formed [6]. [PERSON] et al. and [PERSON] et al. synthesized Cu\({}_{2}\)SnSe\({}_{3}\) nanocrystals and controlled the nanostructure successfully by solvothermal method [7; 8]. In addition to optimizing the preparation process, doping of materials is also an important way to enhance the performance of TE materials. [PERSON] et al. synthesized a Ga-doped Cu\({}_{2}\)Ga\({}_{1-x}\)Ge\({}_{x}\)Se\({}_{3}\) sample and approached its theoretical minimum value of lattice thermal conductivity, resulting in a \(ZT\) value of 0.5 at 750 K [9]. [PERSON] et al. reported a lower lattice thermal conductivity of the Cu\({}_{2}\)Ga\({}_{0.075}\)Sn\({}_{0.925}\)Se\({}_{3}\) sample and obtained a maximum \(ZT\) of 0.43 at 700 K [10]. In addition, [PERSON] et al. confirmed that substituting Se with S is also an effective method to improve the TE performance of Cu-based ternary selenides [11]. The combustion synthesis method can prepare high-performance thermoelectric materials, but it is difficult to precisely control.