Energy recycling under ambient illumination for internet-of-things using metal/oxide/metal-based colourful organic photovoltaics.

Colorful indoor organic photovoltaics (OPVs) have gained considerable attention in recent years for their autonomous function in Internet of Things (IoT) devices. In this study, a solution-processed TiO2 layer in a metal-oxide-metal (MOM) color filter electrode was used for light energy recycling in P3HT:ICBA-based indoor OPVs. The MOM electrode permits tuning of the optical cavity mode to maximize photocurrent production by modulating the thickness of the TiO2 layer in the sandwich structure. This approach preserves the optoelectronic properties of the OPVs without damaging the photoactive layer and allows them to display various vivid colors. The optimized MOM-OPVs demonstrated an excellent power-conversion efficiency (PCE) of 8.8% ± 0.2%, which is approximately 20% higher than that of reference opaque OPVs under 1000-lx light emitting diode (LED) illumination. This can be attributed to the high photocurrent density due to the nonresonant light reflected from metals into the photoactive layer. Additionally, MOM-OPVs exhibit high external quantum efficiency and large parasitic shunt resistances, leading to improved fill factor and PCE values. The proposed MOM electrode provides excellent feasibility for realizing colorful and efficient indoor OPVs for IoT applications.