A self-powered photoactive room temperature gas sensor based on a porphyrin-functionalized ZnO nanorod/p-Si heterostructure

Abstract

The integration of self-powered photodetectors and highly selective gas sensors into a unified system has revolutionized the development of next-generation optoelectronic gas sensors towards overcoming the limitations of high power consumption and poor selectivity in traditional systems. In this scenario, this work describes a superior optoelectronic gas sensor based on 5-(4-carboxyphenyl)-10,15,20-triphenyl porphyrin (H₂TPPCOOH)-functionalized vertically aligned 1D ZnO nanorods grown on p-Si. The dual impact of porphyrin functionalization on the powering and chemical sensing properties of the ZnO NR/p-Si heterostructure was investigated. The resulting porphyrin-functionalized device demonstrated a maximum V_OC of 0.1 V and I_sc of 12.16 μA with good sensitivity and fast response towards triethylamine (TEA) vapors at room temperature. The level of defects in the device and the gas sensing mechanism were studied using the Scanning Kelvin Probe system, and the photoelectric mechanism is explained through energy band diagrams. The ambipolar charge transport in the device plays a significant role in chemical sensing at room temperature at zero power consumption. Hence, this work offers valuable insights for designing self-sustained, stable, cost-effective, miniaturized smart chemical sensors, which are highly selective to specific V_OC biomarkers in complex gas mixtures, with a potential for on-chip integration and point-of-care health monitoring.