  One of the most viable renewable energies is solar power because of its
versatility, reliability, and abundance.In the market, a majority of the solar
panels are made from silicon wafers.These solar panels have an efficiency of
26.4 percent and can last more than 25 years.The perovskite solar cell is a
relatively new type of solar technology that has a similar maximum efficiency
and much cheaper costs, the only downside is that it is less stable and the
most efficient type uses lead.The name perovskite refers to the crystal
structure with an ABX3 formula of the perovskite layer of the cell.All
materials possess a property called a band gap.The smaller the band gap the
more conductive the material, but this does not necessarily mean that the
smaller the band gap the better the solar cell.The Shockley-Queisser limit
provides the optimal band gap in terms of efficiency for a single junction
solar cell which is 1.34 eV for single junction cells.This research focuses on
tuning the band gap of lead-free perovskites through B-site cation replacement.
Through this investigation, the optical band gaps of tin and lead perovskites
were re-established.However, the copper-based perovskite disagrees with
existing DFT calculations.Additionally, the mixed tin and copper perovskite in
this experiment contradicts the intuitive prediction.
