Technoeconomically competitive four-terminal perovskite/graphene-silicon tandem solar cells with over 20% efficiency

Perovskite/Silicon (PS) tandem solar cells have attracted much interest over recent years. However, the most popular crystalline silicon solar cells utilized in tandems require complicated fabrication processes mainly including texturization, diffusion, passivation and metallization, which takes up much cost in photovoltaic market. Here, we report a facile graphene/silicon (Gr/Si) solar cell featuring of low-temperature (≤200 °C) processing and an efficiency of 13.56%. For reducing the heat dissipation loss of high energy photon, the perovskite solar cell (PSC) with a wide band gap of 1.76 eV was adopted as the top cell for the tandem. To reduce the loss of parasitic absorption in hole transport layers (HTLs), thickness of Spiro-OMeTAD is re-optimized by compromising the efficiency and the optical transmittance of the devices. As a result, the semitransparent top perovskite solar cell yields a highest efficiency of 13.35%. Furthermore, we firstly achieved a low-temperature-processed four-terminal (4-T) perovskite/graphene-silicon (PGS) heterojunction tandem solar cell with the efficiency of 20.37%. The levelized cost of electricity (LCOE) of PGS 4-T modules were estimated to a competitive price, exhibiting much greater potential for practical application compared to that of PS 4-T modules.