code: def calc_efficiency(self):
          
          cell_power = self.calc_power_density()
          solar_power = self.calc_blackbody_radiant_power_density()
          efficiency = cell_power/solar_power
  
          return efficiency.decompose().value
docs: Solar cell efficiency
  
          The efficiency is calculated according to Shockley & Queisser's :cite:`10.1063/1.1736034` Eq. 2.8. This method returns a :class:`float`.