| Back Amorphous-Crystalline silicon Heterojunction (BACH) solar cells which combine the benefits of back contact and heterojunction silicon solar cells have been fabricated at the University of Toronto. p- and n-type amorphous silicon deposited at low temperature (∼<200°C) by DC Saddle-Field PECVD system forms interdigitated hetero-emitter and base contacts on the rear-side. A photolithography approach using thermal oxide for electrical isolation demonstrates the proof-of-concept. Three methods for fabricating simplified and advanced BACH cells were explored. The best performing 1 cm 2 cell showed an AM1.5G conversion efficiency of 8.11%, VOC = 0.536 V, JSC = 20.1 mA/cm2 and FF = 75.5%. The BACH cell performance is limited by poor surface passivation and un-optimized cell design. With completely low temperature processing, highly passivated front and rear surfaces, and independent optimization of front-side optical antireflective features and rear-side electrical junctions and contacts, the BACH cell has the potential of becoming highly cost competitive. |
