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.