A research group led by Prof. Liu Shengzhong from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) and Prof. Yang Dong at Shaanxi Normal University have developed high efficiency semi-transparent perovskite solar cells by using MoO3 sandwiched gold nanomesh (MoO3/Au/MoO3) multilayer as the transparent electrode. Combined with a superior heterojunction silicon solar cell, a high efficiency four-terminal perovskite/silicon tandem solar cell was obtained.
Tandem/multijunction structure has been proven to be an effective way to break the Shockley-Queisser limit. To obtain a high efficiency tandem solar cell, the key is to fabricate transparent electrode with high conductivity as well as high transparency through a mild method.
To obtain the highly conductive and transparent electrode, the group demonstrated a MoO3/Au/MoO3 multilayer fabricated by thermal evaporation. The thermal evaporation is mild and will not damage the underneath layer.
The large surface tension of MoO3 improves wettability for gold, resulting in Frank–van der Merwe growth to produce an ultrathin gold nanomesh layer, which guarantees not only excellent conductivity but also great optical transparency. The top MoO3 layer reduces the reflection at the gold layer to further increase light transmission.
As a result, the semitransparent perovskite cell shows an efficiency of 18.3%, which the team stated was the highest ever reported for this type of devices. When the semitransparent perovskite device is mechanically stacked with a heterojunction silicon solar cell of 23.3% PCE, it yields a combined efficiency of 27.0%, higher than those of both the sub-cells. This breakthrough in elevating the efficiency of semitransparent and multijunction/tandem devices can help to break the Shockley–Queisser limit.