Results of comparative, experimental studies on the reversible, metastable, ultrafast photoinduced electron transfer from semiconducting, conjugated polymers onto C-60 are summarized. Photoinduced absorption in millisecond and femtosecond time scales, steady state and picosecond time-resolved photoluminescence, steady state and picosecond transient photoconductivity, steady state infrared photoexcitation spectroscopy and finally steady state Light induced electron spin resonance measurements are summarized as experimental evidence for an ultrafast (< 1 picosecond) forward electron transfer resulting in a long-lived charge separated state. Comparative studies demonstrate that in degenerate ground state polymers soliton excitations, and in polydiacetylenes the strongly bound excitons, form before the electron transfer occurs; thereby inhibiting charge separation. Utilizing thin films of the semiconducting polymer and buckminsterfullerene to form a heterojunction interface, we have fabricated donor-acceptor diode bilayers which functioned as photodiodes and photovoltaic cells.