On the optoelectronic performance of solution-processable N-(4-methoxy-2-nitrophenyl) acetamide microrods thin films for efficient light detection applications

Abstract

Micro and nanostructured organic thin films offer flexible and scalable ways for high-performance organic/inorganic optoelectronics. Consequently, herein, N-(4-methoxy-2-nitrophenyl) acetamide (4M2NPA) thin films are prepared using a solution-processable spin coating technique at different thicknesses. The thickness-dependent structural parameters such as crystallite size and microstrain are estimated and enhanced with film thickness. The FESEM micrographs showed the microrod-based films with a diameter of range (0.40–0.65) μm and a length in the range of (1.5–2) μm. Moreover, the linear optical transmittance, reflectance, and absorbance of the fabricated 4M2NPA thin films are measured in the range of (190–2500) nm. The dispersion behavior of the prepared films is analyzed and explained based on the single oscillator model. Additionally, the increment of film thickness induced a decrease in the energy gap, Eg, from 2.34 to 2.24 eV, and an increase of Urbach energy, Eu, from 125.6 eV to 132.8 meV. The oscillator strength and electric dipole strength are calculated and interpreted in detail. The thickness-dependence of the microelectronic parameters of the manufactured Ag/4M2NPA/p-Si/Al heterojunction is evaluated from the measured dark current-voltage relation. The photoresponse of the implemented heterojunctions with different thicknesses of the organic layer is observed with enhanced photocurrent. The light sensor's figures of merit such as responsivity, specific detectivity, linear dynamic range, and signal to noise ratio showed a thickness-dependent behavior and were found to be 45.26 mA/W, 2.09 × 1010 Jones, 49.85 dB, and 310.7, respectively for the highest thickness of 4M2NPA. Furthermore, the fabricated heterojunction devices showed a fast and stable switching response with trise/tfall ∼ 51 ms/45 ms for the thickest 4M2NPA film.