Inkjet printing of zinc oxide and P3HT:ICBA in ambient conditions for inverted bulk heterojunction solar cells

The third-generation organic solar cells have the benefits of low-cost, solution processability, low energy payback time, environment friendliness and appropriateness for mass production via large area printing techniques. The electron transport layer improves the ohmic contact between the cathode and the photoactive layer. In this research article, we demonstrate a drop on demand inkjet printing of the zinc oxide electron transport layer and the photoactive layer blend consisting of a donor poly(3-hexylthiophene-2,5-diyl) (P3HT) and acceptor Indene C-60 bisadduct (ICBA) of an organic solar cell. Consequently, all inkjet printed solar cell achieved a power conversion efficiency of 4.7% under ambient conditions. We highlighted that drop spacing, substrate temperature and the waveform parameters such as voltage and time are the important parameters for printing. Moreover, we observed a difference in morphology between spin coated and inkjet printed devices as characterized via UV–Visible absorbance, atomic force microscopy and scanning electron microscopy. Furthermore, we applied device characterization from impedance spectroscopy to elucidate the difference in device performance. Particularly, the effective lifetime and global mobilities calculated from the impedance spectroscopy Nyquist plots at 1 Voltage bias in the dark for all inkjet-printed devices are 0.0374 μs and 57.5 × 10⁻³ cm²/V–S respectively, and for all, spin-coated devices are 0.0628 μs and 115.3 × 10⁻³ cm²/V–S respectively.