Structural and Compositional Properties of Recrystallized CdS/CdTe Thin-Films Grown on Oxidized Silicon Substrates

Abstract

Cadmium telluride (CdTe) thin-films are the most promising photovoltaic (PV) materials for lightweight and flexible solar cells because of their excellent light absorption (i.e., direct band-gap of 1.45 eV) and low-cost manufacturing processes. To improve the specific power (kW kg -1 ) and mechanical flexibility, recent research has focused on new PV design and low-temperature (< 450 °C) deposition processes, where the active n-CdS/p-CdTe layers are directly deposited on lightweight substrates, such as polymer [1, 2] and metal foils [3]. However, the measured PV efficiencies of these low-temperature devices (< 14 %) are still far below than those fabricated using high-temperature processing methods (> 22 %). Recognizing this temperature imparity, our approach is based on high-temperature CdTe synthesis (> 450 °C) on an oxidized silicon wafer (Si/SiO2) that can decouple the high-temperature grain growth and the subsequent thin-film lift-off / transfer processes (Figure 1). This method enables the integration of the high-quality CdS/CdTe active layers on lightweight and flexible substrates (e.g., plastic, fabric, cellulose paper) that have having the limited temperature tolerance.