A dark notch is generated by using an amplitude mark to cross partially spatially incoherent light beam.The notch is imaged onto the input face of the crystal.The full width at half maximum of notch is 16.75 μm.Power of input beam is 400 μW.Based on the bulk photovoltaic effect,a pair of Y-junction dark photovoltaic solitons is written with partially spatially incoherent light beam when the background illumination is absent.The experimental result demonstrates that Y-junction dark photovoltaic solitons can be written in LiNbO3:Fe crystal without background illumination.