For last several decade, although intensive researches has been conducted, the maximum power-conversion-efficiency (PCE) of Si solar cells has been economically limited to ~25%. Since Si solar cells absorbed mainly photons in visible wavelength, the silicon solar cells using energy-down-shift (EDS) mechanism has been recently proposed. Un-doped core/shell quantum dots such as CdSe/ZnS or Cd_0.5Zn_0.5S/ZnS have well demonstrated EDS by the Stokes shift of 52~127 nm and enhances ~1% of the PCE in the Si solar cells by implementing them on the Si solar-cell surface¹. In addition, environment-safe InP/ZnS core/shell quantum dots well demonstrated the PCE enhancement of the Si solar cells. However, such small Stokes shift from core/shell quantum dots led the Si solar cell surface to resorb partially the emitting blue light so that the possible PCE enhancement would be limited to ~1%. Recently, the higher than ~200 nm of the Stokes shift from Mn²⁺-doped Cd_0.5Zn_0.5S/ZnS core/shell quantum dots has been demonstrated and enhances ~0.5% of the PCE in Si solar cells. Since Mn²⁺-doped Cd_0.5Zn_0.5S/ZnS core/shell quantum dots basically performs a lower quantum yield (~51%) so that their PCE enhancement would be limited to less than 1%². Thus, another challenge such as energy-up-conversion through the core/shell quantum dots is necessary to overcome the limit of EDS in enhancing the PCE of Si solar cells. In this presentation, we will discuss these issues.

Reference

1. S.W.Baek, J.H.Shim, H.M.Seung, G.S.Lee, J.P.Hong, K.S.Lee, and J.G.Park, Nanoscale, 6, 12524 (2014).
2. M.Jalalah, Y.H.Ko, F.A.Harraz, M.S.Al-Assiri, and J.G.Park, Nano Energy, 33, 257 (2017)