RESUMEN
Two-dimensional (2D) molybdenum ditelluride (MoTe2) exhibits an intriguing polymorphic nature, showing stable semiconducting 2H and metallic 1T' phases at room temperature. Polymorphism in MoTe2 presents new opportunities in developing phase-change memory, high- performance transistors, and spintronic devices. However, it also poses challenges in synthesizing homogeneous MoTe2 with a precisely controlled phase. Recently, a new yet simple method using sputtering and 2D solid-phase crystallization (SPC) is proposed for synthesizing high-quality and large-area MoTe2. This study investigates the polymorphism control of MoTe2 synthesis using 2D SPC. The Te/Mo ratio and oxygen content in the as-sputtered films correlate strongly with the final phase and electrical properties of SPC MoTe2. Furthermore, the SPC thermal budget may be exploited for stabilizing a deterministic phase. The comprehensive experiments presented in this work demonstrate the versatile and precise controllability on the MoTe2 phase by using the simple 2D SPC technique.
RESUMEN
A nontoxic hydrogen-assisted solid Se vapor selenization process (HASVS) technique to achieve a large-area (40 × 30 cm(2)) Cu(In,Ga)Se2 (CIGS) solar panel with enhanced efficiencies from 7.1 to 10.8% (12.0% for active area) was demonstrated. The remarkable improvement of efficiency and fill factor comes from improved open circuit voltage (Voc) and reduced dark current due to (1) decreased interface recombination raised from the formation of a widened buried homojunction with n-type Cd(Cu) participation and (2) enhanced separation of electron and hole carriers resulting from the accumulation of Na atoms on the surface of the CIGS film. The effects of microstructural, compositional, and electrical characteristics with hydrogen-assisted Se vapor selenization, including interdiffusion of atoms and formation of buried homojunction, were examined in detail. This methodology can be also applied to CIS (CuInSe2) thin film solar cells with enhanced efficiencies from 5.3% to 8.5% (9.4% for active area) and provides a facile approach to improve quality of CIGS and stimulate the nontoxic progress in the large scale CIGS PV industry.
