where 𝐵 is the spectral radiance, 𝜆 is the wavelength, 𝑇 is the temperature, ℎ is Planck's constant, and 𝑐 is the speed of light. Table : Simulated (pvTrace v2.1sv) external photon efficiency for a variety of hypothetical bulk LSC designs using enclosing box or surface normal methods of ray counting. The sample numbers correspond to the bulk LSCs illustrated in Figure . For all parts the following conditions were applied: (i) top surface area of 6.25 cm 2 ; (ii) thickness of 0.21 cm; (iii) LR305 concentration = 500 ppm; (iv) refractive index = 1.5; (v) waveguide parasitic absorption of 0.525 cm -1 ; (vi) incident spectrum of 300-900 nm. The x-and y-dimensions of the enclosing box were set 101% of the actual x-and ydimensions of the LSC, while the z-dimension was 110% of the actual z-dimension of the LSC. . For all parts the following conditions were applied: (i) top surface area of 6.25 cm 2 ; (ii) thickness of 0.21 cm; (iii) LR305 concentration = 500 ppm; (iv) refractive index = 1.5; (v) waveguide parasitic absorption of 0.525 cm -1 ; (vi) incident spectrum of 300-900 nm. The x-and y-dimensions of the enclosing box were set 101% of the actual x-and y-dimensions of the LSC, while the z-dimension was 110% of the actual zdimension of the LSC.