High-Quality ITO/Al-ZnO/n-Si Heterostructures with Junction Engineering for Improved Photovoltaic Performance

• Main Authors: Chong Tong, Manjeet Kumar, Ju-Hyung Yun, Joondong Kim, Sung Jin Kim
• Format: Article
• Language: English
• Published: MDPI AG 2020-07-01
• Series: Applied Sciences
• Subjects: Al-ZnO/Si heterojunction photovoltaic; junction engineering; built-in potential; thin film stress release
• Online Access: https://www.mdpi.com/2076-3417/10/15/5285

A heterostructure of Sn-doped In₂O₃(ITO)/Al-doped ZnO (AZO)/n-Si was proposed and studied for photovoltaics. The top ITO worked as a transparent conducting layer for excellent optical transparency and current collection. The AZO/n-Si served as the active junction and provided the built-in potential (<i>qV_bi</i>) for the photovoltaic devices. To achieve a higher open circuit voltage (V_oc), which is the main challenge for AZO/Si heterojunctions due to the junction interfacial defects, the AZO and AZO/Si junction properties were systematically investigated. By modulating the Al doping in the AZO thin films via a dual beam co-sputtering technique, the AZO/n-Si junction quality was significantly improved with <i>qV_bi</i> increased from 0.21 eV to 0.74 eV. As a result, the V_ocof our best device was enhanced from 0.14 V to 0.42 V, with a short circuit current (J_sc) of 26.04 mA/cm² and a conversion efficiency (E_ff) of 5.03%. To our best knowledge, this is the highest V_oc reported for ZnO/Si heterojunctions prepared by the sputtering method. The results confirmed the validity of our proposed structure and junction engineering approach and provided new insights and opportunities for ZnO/Si heterojunction optoelectronics.