(nm)

Under these conditions, the quantum efficiency is directly proportional to the absorption coefficient. Figure 5 illustrates this relationship for anthracene heavily doped with tetracene. The results in Figs. 4 and 5 are in good agreement with the model. Mulder’s values for the diffusion length of undoped anthracene were between 400 and 600 A, in agreement with earlier work of Simpson (1956). For

tetracene doped (2 x 10-4 M) anthracene, the diffusion length was 80 A. Mulder’s results, in conjunction with earlier studies, led to the general conclusion that anthracene was an extrinsic photoconductor.