In　the　reported　fabrication　process　of　organic　photovoltaics　(OPVs),　the　effects　of　the　light　environment　are　usually　thought　to　be　negligible,　and　so　are　not　included　in　the　experimental　section　of　a　paper.　In　this　work,　the　morphology　of　organic　bulk-heterojunction　(BHJ)　photovoltaics　in　the　presence　and　absence　of　white　light　during　the　film　formation　process　was　examined　by　using　small-angle　neutron　scattering　and　grazing　incidence　X-ray　scattering.　We　provide　the　first　clear　experimental　evidence　that　the　morphology,　thermodynamics　and　function　of　BHJ　blends　are　significantly　impacted　by　photo　absorption　during　the　film　formation　process.　The　results　clearly　demonstrate　that　the　crystal　sizes　of　donor　materials　decrease,　while　the　size　of　the　pure　acceptor　phase　increased　with　an　increase　in　the　light　intensity　along　with　enhanced　acceptor　aggregates.　Moreover,　the　specific　interfacial　area　between　the　pure　acceptor　phase　and　its　surrounding　matrix　is　found　to　be　crucial　for　the　electron　transport　and　device　performance,　which　reaches　a　maximum　under　1　sun　illumination,　resulting　in　the　best　device.　The　generalization　of　the　impact　of　light　illumination　was　also　investigated　in　other　OPV　systems,　including　the　fullerene　and　non-fullerene　systems.　These　findings　opened　the　door　to　a　wide　range　of　applications,　such　as　providing　simple　illumination　during　the　processing　of　organic　semiconductor-based　devices　to　precisely　control　the　morphology,　and　surely　expend　the　application　of　illumination　for　further　improvements　in　the　OPV　performance.　This　journal　is　©　The　Royal　Society　of　Chemistry.