Achieving >28% power conversion efficiency in a-Si:H/c-Si solar cells through emitter optimization

Heterojunction solar cell efficiency is crucial for performance and commercial viability. This study investigates hydrogenated microcrystalline silicon (μc-Si:H), hydrogenated nanocrystalline silicon (nc-Si:H), and hydrogenated amorphous silicon germanium (a-SiGe:H) as p-type emitter layers in a-Si:H/c-Si heterojunction solar cells, examining their influence on short-circuit current density (Jsc), open-circuit voltage (Voc), fill factor (FF), and power conversion efficiency (PCE). Considering the reported effects of hydrogen dilution and substrate temperature on the optoelectronic properties of these materials [1, 2], we employed AMPS-1D simulations to model device performance with various emitter layers (a-Si:H(p), nc-Si:H(p), μc-Si:H(p), a-SiC:H(p), and a-SiGe:H(p)). A baseline (PCE) of 27.38% was achieved using a standard a-Si:H(p) emitter (1.8 eV bandgap). Alternative emitters yielded improved PCEs: nc-Si:H(p) (28.26% at 1.9 eV), μc-Si:H(p) (28.04% at 1.5 eV), and a-SiGe:H(p) (28.18% at 1.7 eV). These enhancements are attributed to the wider bandgaps, higher conductivity, and lower defect densities of these materials, resulting in reduced recombination losses and enhanced carrier collection. Our findings demonstrate the significant potential of emitter layer optimization for maximizing a-Si:H/c-Si heterojunction solar cell power conversion efficiency.