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 ( ${D}^{\ast } $ ), and transparency. Remarkably high R of 9040, 64.0, and 2.0 A/W and ${D}^{\ast } $ of $1.32\times 10^{{15}}$ , $2.86\times 10^{{12}}$ , and $1.10\times 10^{{11}}$ 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 ( ${d}_{\text {C60}}$ ) revealed a strong dependence of both R and ${D}^{\ast } $ on ${d}_{\text {C60}}$ . For shorter wavelengths (405 and 450 nm), the maxima of ${R} \sim {d}_{\text {C60}}$ curves were observed around ${d}_{\text {C60}} =10$ nm, whereas for longer wavelengths (532, 650, and 850 nm), they appeared at around ${d}_{\text {C60}} =5$ nm. The maxima of ${D}^{\ast } \sim {d}_{\text {C60}}$ curves were consistently located at ${d}_{\text {C60}} =5$ nm for all measured wavelengths. Further investigations on the impact of CuPc layer thickness ( ${d}_{\text {CuPc}}$ ) indicated that the device achieved maximal R and ${D}^{\ast } $ at ${d}_{\text {CuPc}} =2$ 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 ${d}_{\text {CuPc}} =40$ nm, while ${D}^{\ast } $ peaked at ${d}_{\text {CuPc}} =2$ 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.