Bifacial Si heterojunction-perovskite organic-inorganic tandem to produce highly efficient (ηT* ∼ 33%) solar cell

As single junction photovoltaic (PV) technologies, both Si heterojunction (HIT) and perovskite based solar cells promise high efficiencies at low cost. Intuitively, a traditional tandem cell design with these cells connected in series is expected to improve the efficiency further. Using a self-consistent numerical modeling of optical and transport characteristics, however, we find that a traditional series connected tandem design suffers from low J(SC) due to band-gap mismatch and current matching constraints. Specifically, a traditional tandem cell with state-of-the-art HIT (eta = 24%) and perovskite (eta = 20%) sub-cells provides only a modest tandem efficiency of eta(T) similar to 25%. Instead, we demonstrate that a bifacial HIT/perovskite tandem design decouples the optoelectronic constraints and provides an innovative path for extraordinary efficiencies. In the bifacial configuration, the same state-of-the-art sub-cells achieve a normalized output of eta(T)* = 33%, exceeding the bifacial HIT performance at practical albedo reflections. Unlike the traditional design, this bifacial design is relatively insensitive to perovskite thickness variations, which may translate to simpler manufacture and higher yield. (C) 2015 AIP Publishing LLC.