Tandem Organic Light-Emitting Diode and Organic Photovoltaic Device Inside Polymer Dispersed Liquid Crystal Cell

We have demonstrated a vertically stacked device consisting of organic photovoltaic device (OPV) and organic light-emitting diode (OLED) inside a polymer dispersed liquid crystal (PDLC) cell. In such a device, OLED and PDLC acted as transmissive- (T-) and reflective- (R-) mode, respectively, of a transflective display without the tradeoff of aperture ratio between R- and T-modes in a conventional transflective LC display. OPV functioned as the black background for PDLC operation and increased the contrast ratio of OLED. Electrical characteristics of OLED and OPV in the stacked device were nearly identical to their individual device, which showed the fabrication process had little effect on OLED and OPV performances. However, their optical properties showed a little degradation, coming from the multi-layer structure and hence the suitable optical cavity design was needed. Storage lifetime of OLED increased in the stacked device because LC material helped to prevent the water and oxygen attack. Driving voltage of PDLC increased due to the insertion of passivation layer upon the electrode which was used protect the OLED and OPV underneath.