The cross-sectional structure of the fabricated bulk heterojunction OPV devices is illustrated in Fig. 1. The glass
substrates were cleaned by sequential ultrasonic treatment in detergent, de-ionized water, acetone, and isopropyl alcohol
for 20 minutes, and were then treated by UV-ozone for 15 min to improve the wettability for further processes. The
transparent anode is composed of inkjet-printed Ag grids between two spin-coated poly(3,4-ethyJenedioxythiophene):
poly(styrenesulfonate) (PEDOT:PSS) layers. The PEDOT:PSS (CLEVIOS™ PH500 purchased from H.C.Starck)
solution was modified with 5% DMSO, and then sonicated for 10 min before use. The first PEDOT:PSS layer was spincoated
onto the UV -ozone treated glass and annealed at 120°C for 10 min to achieve the thickness of about 30 nm. The
non-particle type silver ink for inkjet printing was supplied from Kunshan Hisense Electronics, China. The ink viscosity
and surface tension were tuned to allow the ink to be jettable through a 10 pL cartridge associated with the Dimatix DMP
2800 drop-on-demand piezoelectric inkjet printer system. The inkjet-printed Ag grid was annealed at 150°C for 10 min
to achieve good conductivity. The second PEDOT:PSS layer was then spin-coated on top of the Ag grids to complete the
anode process.