We report steady state 5.49 MeV alpha particle detection results using organic semiconductor diodes fabricated using a blend of poly(3-hexylthiophene) and phenyl-c61-butyric acid methyl ester, under modest bias conditions (up to ±20 V). Alpha particle device sensitivities between 10^4 and 10^7 nC mGy^-1 cm^-3 are achieved (depending on individual device and drive conditions). The alpha particle charge detection efficiencies are compared to transient and steady state photoconduction charge detection efficiencies for the same devices. Trapped electrons within the organic blend induce significant current gain in forward biased devices, both in photoconduction and in alpha detection. Results indicate that the photoconductive charge generation efficiency is a viable proxy for the alpha particle device sensitivity or detection efficiency, given the approximately linear experimental relationship between them. Hecht equation fitting of the collected charge-electric field results obtained returns mobility-lifetime values of order 10^-7 cm^2 V^-1, consistent with Time of Flight results for the same devices. The results provide proof of principle that large area, solution processed, organic semiconductor based diodes can achieve high sensitivity alpha detection without requiring high bias drive conditions or the growth of single, large molecular crystals.