Solution-processed hybrid light emitting and photovoltaic devices comprising zinc oxide nanorod arrays and tungsten trioxide layers

The goal of this research is to prepare inverted optoelectronic devices with improved performance by combining zinc oxide (ZnO) nanorod arrays and tungsten trioxide (WO₃) layer. ZnO seed layers with thickness of 52 nm were established, followed by growth of ZnO nanorods with length of 300 nm vertical to the ITO substrates in the precursor bath. The ZnO nanorod arrays possess high transmittance up to 92% in the visible range. Inverted light-emitting devices with the configuration of ITO/ZnO nanorods/ionic PF/MEH-PPV/PEDOT:PSS/Au were constructed. The best device achieved a max brightness and current efficiency of 10,620 cd/m² and 0.25 cd/A at 10 V, respectively, revealing much higher brightness compared with conventional devices using Ca/Al as cathode, or inverted devices based on ZnO thin film. By inserting a WO₃ thin layer between PEDOT:PSS and Au electrode, the max brightness and current efficiency were further improved to 21,881 cd/m² and 0.43 cd/A, respectively. Inverted polymer solar cells were also fabricated with the configuration of ITO/ZnO nanorods/ionic PF/P3HT:PC61BM/PEDOT/WO₃/Au. The best device parameters, including the open-circuit voltage, short-circuit current density, fill factor, and power conversion efficiency, reached 0.54 V, 14.87 mA/cm², 41%, and 3.31%, respectively.