Spectral Splitting Solar Cells Constructed with InGaP/GaAs Two-Junction Subcells and Infrared PbS Quantum Dot/ZnO Nanowire Subcells

We constructed an infrared PbS colloidal quantum dot (QD)/ZnO nanowire (NW) solar cell to develop a solution-processed bottom solar cell for multijunction solar cells. PbS QD/ZnO NW interdigitated structures comprising 1 μm long ZnO NWs enable the construction of spatially separated carrier pathways and thick PbS QD layers for high infrared light harvesting. Additionally, optical management plays an essential role in the harvesting process. Using infrared transparent conductive oxides as window layers and a wide-band-gap QD electron blocking layer (EBL), the parasitic absorption of the EBL is reduced and the reabsorption of the light reflected is enhanced by the metal back contact. Thus, the developed solar cell produced a short-circuit current density of 39.2 mA/cm2 under 1 sun illumination and 17.4 mA/cm2 over an 870 nm infrared region. Furthermore, series-connected spectral splitting solar cells, comprising an InGaP/GaAs top/middle (2J-TM) subcell and the infrared PbS CQD/ZnO NW bottom (1J-B) subcell, yielded a power conversion efficiency of 30.5% under 1 sun illumination.