다이오드 레이저 어닐링 공정을 적용한 태양전지용 CdTe 박막 특성

Abstract

Laser annealing has some advantages, including excellent annealing selectivity to the underlayers for a short duration and precise control of the heating time with localized high temperature. Laser annealing has a superior ramp-up rate (up to 108 times higher) compared to the rapid thermal process (RTP). Multi-layered devices require precise control of the annealing process in order to realize negligible diffusion and very low sheet resistance. Heterostructured thin-film solar cells also require a selective annealing process in order to avoid inter-diffusion with the underlayers or substrate during the annealing process. Cadmium telluride (CdTe) is a II-VI compound semiconductor and has attracted considerable attention as a photovoltaic absorber in thin-film solar cells owing to its direct band gap (Eg) of 1.45-1.50eV, high absorption coefficient (α)≥104 cm-1, flexibility and large-scale commercialization. The laser annealing process is performed restrictively in silicon solar cell applications for crystallization and grain growth to improve the efficiency, but few studies have evaluated thin-film solar cell applications.