Highly efficient, transparent and stable semitransparent colloidal quantum dot solar cells: a combined numerical modeling and experimental approach†
Semitransparent solar cells (SSCs) can open new photovoltaic applications in many areas. However, because of the fundamental trade-off between optical transparency and photovoltaic efficiency, it is of special importance to minimize additional optical losses such as from reflectance and parasitic absorption. In this work, a semitransparent colloidal quantum dot solar cell (SCQDSC) with high efficiency, transparency and stability is investigated using a coupled theoretical and experimental approach. Extensive numerical simulations and experimental investigations are performed for optimizing the device transparency and efficiency simultaneously. The results show that the transparency and efficiency are largely enhanced as a result of lowering the optical losses in the SCQDSC, and the device exhibits a high efficiency of 7.3% with an average visible transmittance of 20.4%. Importantly, the SCQDSC exhibits very good stability under long term continuous illumination and the unencapsulated SCQDSCs show no large degradation in performance during storage for 70 days under ambient conditions. These findings suggest that the SCQDSC has high potential for applications, such as for building integrated photovoltaics, automobiles or screens. Moreover, this work also provides practical and quantitative guidelines for further enhancing the SSC performance.