From 11% Thin Film to 23% Heterojunction Technology (HJT) PV Cell: Research, Development and Implementation Related 1600 × 1000 mm2 PV Modules in Industrial Production

Abstract

Plasma-enhanced chemical vapor deposition (PECVD) developed for thin film (TF) Si:Hbased materials resulted in large area thin film PV cells on glass and flexible substrates. However, these TF cells demonstrate low power conversion efficiency PCE = 11% for double and PCE = 13% for triple junction cells below predicted PCE ≈ 24%. PV cells on crystalline silicon (c-Si) provide PCE ≈ 17–19%. Cost of c-Si PV cells lowered continuously due to reducing price of silicon wafers and enlarging their size. Two factors stimulated a combination of PECVD films and c-Si devices: (a) compatibility of the technologies and (b) possibility for variation of electronic properties in PECVD materials. The latter results in additional build-in electric fields improving charge collection and harvesting solar spectrum. We describe a transformation of PECVD TF solar cell technology for 11% efficiency modules to heterojunction technology (HJT) c-Si modules with 23% efficiency. HJT PV structure comprises c-Si wafer with additional junctions created by PECVD deposited layers allowing development of single wafer PV cells with PCE ≈ 24% and the size limited by wafer (15.6 x 15.6 cm2). The chapter starts with background in PECVD and c-Si PV cells. Then, in Section 2, we describe electronic properties of PECVD materials in HJT PV structures. Section 3 deals with structure and fabrication process for HJT devices. In Section 4, we present and discuss performance characteristics of the devices. Section 5 describes implementation of the developed HJT module (1600 x 1000 mm2) based on HJT single wafer cells in industry with presentation and discussion of characteristics related to industrial production. Finally, Section 6 presents the outlook and summary of the chapter.