Computer calculation of the power output from a pin solar cell as a function of intrinsic layer thickness. The differing curves indicate results for monochromatic illumination with absorption coefficients from 5000/cm to 100 000/cm; for typical a-Si: H, this range corresponds to a photon energy range from 1.8 to 2.5 eV. Solid symbols indicate illumination through the p-layer and open symbols indicate illumination through the n-layer. Incident photon flux = 2 × 1017/cm2s; no back reflector. The data are obtained from real experiments, with the curves calculated using methods outlined in the references [3-8].