High-Performance Semitransparent Photodiodes Based on Zinc Oxide/C₆₀/Copper Phthalocyanine Double Heterojunction

Photovoltaic devices based on metal oxide and organic semiconductor heterostructure generally exhibit poor performance due to inefficient exciton dissociation at the metal oxide/organic interface. Here, we present an enhancement in the performance of photodiodes fabricated via zinc oxide (ZnO)/C60/copper phthalocyanine (CuPc) double heterojunction solution. This obtained photodiode demonstrates photodetection in the wavelength range of 400–850 nm with high photoresponsivity (R), specific detectivity ( <tex-math notation="LaTeX">D </tex-math> ), and transparency. Remarkably high R of 9040, 64.0, and 2.0 A/W and <tex-math notation="LaTeX">D </tex-math> of <tex-math notation="LaTeX">1.32× 10^15 </tex-math> , <tex-math notation="LaTeX">2.86× 10^12 </tex-math> , and <tex-math notation="LaTeX">1.10× 10^11 </tex-math> Jones were achieved, for representative wavelengths of 405, 650, and 850 nm, respectively. The device exhibited a maximal average, transparency of 0.444 in the wavelength range of 400–1000 nm. Investigation into the effects of C60 layer thickness ( <tex-math notation="LaTeX">dC60 </tex-math> ) revealed a strong dependence of both R and <tex-math notation="LaTeX">D </tex-math> on <tex-math notation="LaTeX">dC60 </tex-math> . For shorter wavelengths (405 and 450 nm), the maxima of <tex-math notation="LaTeX">R ~ dC60 </tex-math> curves were observed around <tex-math notation="LaTeX">dC60 =10 </tex-math> nm, whereas for longer wavelengths (532, 650, and 850 nm), they appeared at around <tex-math notation="LaTeX">dC60 =5 </tex-math> nm. The maxima of <tex-math notation="LaTeX">D ~ dC60 </tex-math> curves were consistently located at <tex-math notation="LaTeX">dC60 =5 </tex-math> nm for all measured wavelengths. Further investigations on the impact of CuPc layer thickness ( <tex-math notation="LaTeX">dCuPc </tex-math> ) indicated that the device achieved maximal R and <tex-math notation="LaTeX">D </tex-math> at <tex-math notation="LaTeX">dCuPc =2 </tex-math> nm for light of wavelength 405 and 450 nm, and at 40 nm for light of wavelength 650 and 780 nm. Specifically, for the light of wave-length 532 nm, R was maximal at <tex-math notation="LaTeX">dCuPc =40 </tex-math> nm, while <tex-math notation="LaTeX">D </tex-math> peaked at <tex-math notation="LaTeX">dCuPc =2 </tex-math> nm. Moreover, optical simulations partially elucidated the physical origin behind these results. The obtained results provide an effective strategy to fabricate high-performance semitransparent photodiodes.