An organic semiconductor obtained with a low-temperature process for light-addressable potentiometric sensors

In this study, the first trial of donor and acceptor bulk heterojunctions (BHJs) is proposed for light-addressable potentiometric sensors (LAPSs) due to organic conjugated molecules with the advantages of energy level/band gap modification and high absorption of visible light. The benzodithiophene-based polymer PTB7-Th and fullerene PC71BM are selected for integration with an Al2O3 sensing membrane using atomic layer deposition at temperatures lower than 100 celcius for pH sensing LAPS. In the stability performance, the hysteresis width of the best condition with a mixing weight ratio of PC71BM to PTB7-Th of 1.5 is 4.4 mV, which is inferior to that of the conventional inorganic semiconductor-based LAPSs. By means of an additional spin-coated zinc oxide (ZnO) layer, the signal-to-noise ratio of the photocurrent of this fabricated LAPS can be maintained at 3.2 after 170 min of measurement with an acceptable sensitivity, linearity, drift coefficient and hysteresis of 50.2 mV/pH, 99.9%, - 3.1 mV/h and 1.4 mV, respectively. With the proper adjustment of illumination with low power and large spots, chemical imaging with a scanning step of 25 mu m can be conducted to indicate the feasibility of this lowtemperature process developed for spin-coated organic semiconductor-based LAPSs.

Automated summary

This study proposes the first trial of using donor and acceptor bulk heterojunctions (BHJs) for light-addressable potentiometric sensors (LAPS) with organic conjugated molecules, which have the advantages of energy level/band gap modification and high absorption of visible light. The chosen materials for integration with an Al2O3 sensing membrane are benzodithiophene-based polymer PTB7-Th and fullerene PC71BM, and they are deposited at temperatures lower than 100 celcius for pH sensing LAPS. By adding a spin-coated zinc oxide (ZnO) layer, the fabricated LAPS shows a signal-to-noise ratio of 3.2 after 170 min of measurement, with acceptable sensitivity, linearity, drift coefficient, and hysteresis.