Schottky‐Barrier‐Controllable Graphene Electrode to Boost Rectification in Organic Vertical P–N Junction Photodiodes

Abstract

Monolayer graphene is used as an electrode to develop novel electronic device architectures that exploit the unique, atomically thin structure of the material with a low density of states at its charge neutrality point. For example, a single semiconductor layer stacked onto graphene can provide a semiconductor-electrode junction with a tunable injection barrier, which is the basis for a primitive transistor architecture known as the Schottky barrier field-effect transistor. This work demonstrates the next level of complexity in a vertical graphene-semiconductor architecture. Specifically, an organic vertical p-n junction (p-type pentacene/n-type N,N′-dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C 8 )) on top of a graphene electrode constituting a novel gate-tunable photodiode device structure is fabricated. The model device confirms that controlling the Schottky barrier height at the pentacene-graphene junction can (i) suppress the dark current density and (ii) enhance the photocurrent of the device, both of which are critical to improve the performance of a photodiode.

Self‐Powered Photodetector Based on β‐Ga 2 O 3 / GaN Heterojunction With Enhanced UV Detectivity

“…This is attributed to the fact that the photon energy is higher than the optical bandgap of both Ga 2 O 3 and GaN layers; in other words, the absorption fraction is dominated by β-Ga 2 O 3 in the layer between 200 to around 256 nm. Where GaN governs the absorption above 363 nm, these outcomes are in well accordance with literature [32,46,52].…”

“…By varying the concentration of donors at Ga 2 O 3 , it can be observed that at reverse bias -2 to 0 V lower doping leads to a wider depletion region; this creates a high volume where the photogenerated carriers are stored. The built-in voltage, which improves the current density at the reverse state, could influence those charge carriers [43,46]. For instance, for 3 × 10 16 and.…”

Self‐Powered Photodetector Based on β‐Ga 2 O 3 / GaN Heterojunction With Enhanced UV Detectivity

“…This is attributed to the fact that the photon energy is higher than the optical bandgap of both Ga 2 O 3 and GaN layers; in other words, the absorption fraction is dominated by β-Ga 2 O 3 in the layer between 200 to around 256 nm. Where GaN governs the absorption above 363 nm, these outcomes are in well accordance with literature [32,46,52].…”

“…By varying the concentration of donors at Ga 2 O 3 , it can be observed that at reverse bias -2 to 0 V lower doping leads to a wider depletion region; this creates a high volume where the photogenerated carriers are stored. The built-in voltage, which improves the current density at the reverse state, could influence those charge carriers [43,46]. For instance, for 3 × 10 16 and.…”

Nanoscale electronic transport at graphene/pentacene van der Waals interfaces

“…8 The result n 1 > n 2 indicates a less ideal Gr/P5 interface than the P5/C-AFM tip one, and it can be related to more defects, impurities at the Gr/P5 interface. Although this parameter was not systematically reported in previous works on Gr/P5 Schottky diodes, 14,21,24,25 we note that the present value is better than ≈3 reported for HOPG/P5 diodes. 21 More interesting, we systematically obtained higher energy barriers for sample B than sample A: ε 1 > Φ B1 and ε 2 > Φ B2 (see Table 2 and 3).…”

Performance Improvement with an Ultrathin p-Type Interfacial Layer in n-Type Vertical Organic Field-Effect Transistors Based on Reduced Graphene Oxide Electrode

“…The LUMO level of PTCDI-C 8 is approximately 4.3 eV. 19 Due to the gatetunable injection barrier height at the rGO/PTCDI-C 8 interface, I D could be effectively modulated under different V G at V D > 0 V. When an ultrathin CuPc interfacial layer was applied, the higher LUMO level (3.5 eV) of CuPc was expected to limit both the on-and off-current densities of the device because of the intrinsically larger injection barrier height at the rGO/CuPc interface. Interestingly, only the off-current density was significantly restrained, whereas the on-current density of the device was slightly enhanced from 0.73 to 0.79 mA/cm 2 .…”

“…The work function of the rGO electrode was estimated to be 5.3 eV using photoelectron yield spectroscopy (Figure S2). The LUMO level of PTCDI-C 8 is approximately 4.3 eV . Due to the gate-tunable injection barrier height at the rGO/PTCDI-C 8 interface, I D could be effectively modulated under different V G at V D > 0 V. When an ultrathin CuPc interfacial layer was applied, the higher LUMO level (3.5 eV) of CuPc was expected to limit both the on- and off-current densities of the device because of the intrinsically larger injection barrier height at the rGO/CuPc interface.…”

Self‐Powered Photodetector Based on β‐Ga 2 O 3 / GaN Heterojunction With Enhanced UV Detectivity

“…This is attributed to the fact that the photon energy is higher than the optical bandgap of both Ga 2 O 3 and GaN layers; in other words, the absorption fraction is dominated by β-Ga 2 O 3 in the layer between 200 to around 256 nm. Where GaN governs the absorption above 363 nm, these outcomes are in well accordance with literature [32,46,52].…”

“…By varying the concentration of donors at Ga 2 O 3 , it can be observed that at reverse bias -2 to 0 V lower doping leads to a wider depletion region; this creates a high volume where the photogenerated carriers are stored. The built-in voltage, which improves the current density at the reverse state, could influence those charge carriers [43,46]. For instance, for 3 × 10 16 and.…”

Nanoscale electronic transport at graphene/pentacene van der Waals interfaces

“…8 The result n 1 > n 2 indicates a less ideal Gr/P5 interface than the P5/C-AFM tip one, and it can be related to more defects, impurities at the Gr/P5 interface. Although this parameter was not systematically reported in previous works on Gr/P5 Schottky diodes, 14,21,24,25 we note that the present value is better than ≈3 reported for HOPG/P5 diodes. 21 More interesting, we systematically obtained higher energy barriers for sample B than sample A: ε 1 > Φ B1 and ε 2 > Φ B2 (see Table 2 and 3).…”

Performance Improvement with an Ultrathin p-Type Interfacial Layer in n-Type Vertical Organic Field-Effect Transistors Based on Reduced Graphene Oxide Electrode

“…The LUMO level of PTCDI-C 8 is approximately 4.3 eV. 19 Due to the gatetunable injection barrier height at the rGO/PTCDI-C 8 interface, I D could be effectively modulated under different V G at V D > 0 V. When an ultrathin CuPc interfacial layer was applied, the higher LUMO level (3.5 eV) of CuPc was expected to limit both the on-and off-current densities of the device because of the intrinsically larger injection barrier height at the rGO/CuPc interface. Interestingly, only the off-current density was significantly restrained, whereas the on-current density of the device was slightly enhanced from 0.73 to 0.79 mA/cm 2 .…”

“…The work function of the rGO electrode was estimated to be 5.3 eV using photoelectron yield spectroscopy (Figure S2). The LUMO level of PTCDI-C 8 is approximately 4.3 eV . Due to the gate-tunable injection barrier height at the rGO/PTCDI-C 8 interface, I D could be effectively modulated under different V G at V D > 0 V. When an ultrathin CuPc interfacial layer was applied, the higher LUMO level (3.5 eV) of CuPc was expected to limit both the on- and off-current densities of the device because of the intrinsically larger injection barrier height at the rGO/CuPc interface.…”

Self‐Powered Photodetector Based on β‐Ga 2 O 3 / GaN Heterojunction With Enhanced UV Detectivity

“…This is attributed to the fact that the photon energy is higher than the optical bandgap of both Ga 2 O 3 and GaN layers; in other words, the absorption fraction is dominated by β-Ga 2 O 3 in the layer between 200 to around 256 nm. Where GaN governs the absorption above 363 nm, these outcomes are in well accordance with literature [32,46,52].…”

“…By varying the concentration of donors at Ga 2 O 3 , it can be observed that at reverse bias -2 to 0 V lower doping leads to a wider depletion region; this creates a high volume where the photogenerated carriers are stored. The built-in voltage, which improves the current density at the reverse state, could influence those charge carriers [43,46]. For instance, for 3 × 10 16 and.…”

Nanoscale electronic transport at graphene/pentacene van der Waals interfaces

“…8 The result n 1 > n 2 indicates a less ideal Gr/P5 interface than the P5/C-AFM tip one, and it can be related to more defects, impurities at the Gr/P5 interface. Although this parameter was not systematically reported in previous works on Gr/P5 Schottky diodes, 14,21,24,25 we note that the present value is better than ≈3 reported for HOPG/P5 diodes. 21 More interesting, we systematically obtained higher energy barriers for sample B than sample A: ε 1 > Φ B1 and ε 2 > Φ B2 (see Table 2 and 3).…”

Performance Improvement with an Ultrathin p-Type Interfacial Layer in n-Type Vertical Organic Field-Effect Transistors Based on Reduced Graphene Oxide Electrode

“…The LUMO level of PTCDI-C 8 is approximately 4.3 eV. 19 Due to the gatetunable injection barrier height at the rGO/PTCDI-C 8 interface, I D could be effectively modulated under different V G at V D > 0 V. When an ultrathin CuPc interfacial layer was applied, the higher LUMO level (3.5 eV) of CuPc was expected to limit both the on-and off-current densities of the device because of the intrinsically larger injection barrier height at the rGO/CuPc interface. Interestingly, only the off-current density was significantly restrained, whereas the on-current density of the device was slightly enhanced from 0.73 to 0.79 mA/cm 2 .…”

“…The work function of the rGO electrode was estimated to be 5.3 eV using photoelectron yield spectroscopy (Figure S2). The LUMO level of PTCDI-C 8 is approximately 4.3 eV . Due to the gate-tunable injection barrier height at the rGO/PTCDI-C 8 interface, I D could be effectively modulated under different V G at V D > 0 V. When an ultrathin CuPc interfacial layer was applied, the higher LUMO level (3.5 eV) of CuPc was expected to limit both the on- and off-current densities of the device because of the intrinsically larger injection barrier height at the rGO/CuPc interface.…”