Research On Performance Of Ternary Organic Photomultiplier Detector Based On Trap Doping

Organic photomultiplier detectors have become the focus of research due to their high External Quantum Efficiency(EQE).Trap doping is an important method to realize current multiplication of organic photodetector,but it still has the problem of low concentration of trap doping.In order to solve the above problems,this thesis adopts a double-doping method of doping two kinds of electron traps in the active layer system of ternary heterojunction P3HT:PTB7:PC61BM.Firstly,organic photomultiplier detector with single-doped C70 trap is studied.The experimental results show that the device doped with 2.5wt%C70 has the best performance.The EQE of single-doped devices under-2V bias,?=460nm,Pin=0.21mW·cm-2 illumination is 421.33%.Then in order to increase the trap doping concentration,while keeping the optimal doping concentration of C 70 unchanged,three double-doped organic photomultiplier detectors,C70:C60,C70:DDQ,and C70:F4-TCNQ,were studied.The experimental results show that the optimal trap doping concentrations of the three types of dual-doped devices are 4.0wt%,4.0wt%and 3.0wt%,respectively,which are about 1.6 times,1.6 times and 1.2 times of those of single-doped devices.Its carrier concentration increased from 4.38×1017cm-3 of a single-doped device to 1.10×1018cm-3,1.23×1018cm-3,1.07×1018cm-3,respectively.It shows that the double doping method can increase the hole tunneling injection of the electrode,increase the photocurrent density,and obtain a high multiplication effect.Therefore,the double-doping method can improve the aggregation phenomenon of dopant,improve the doping concentration and doping efficiency,and obtain the high concentration trap doped active layer.The EQE of the three double-doped devices are 1691.65%,4221.26%and 1117.56%,respectively,which are about 4.66 times,10.02 times and 2.65 times of that of the single-doped devices.The comparative analysis shows that because of the cyanide(-CN)and halogen(chlorine)atoms in DDQ molecule,it has a low LUMO level,which is conducive to electron capture.Therefore,C70:DDQ shows good trap doping effect.While for F4-TCNQ,although it has lower LUMO level,more cyanide(-CN)and halogen(fluorine)atoms in its molecular structure promote the crystallization of P3HT and PTB7 on F4-TCNQ,promote the agglomeration of F4-TCNQ,affect its dispersion,and reduce the doping efficiency.Thus,the hole injection effect from Al cathode is weakened.In conclusion,the double-doping method can effectively increase the trap doping concentration of the active layer,thus improving the external quantum efficiency and photomultiplier of the device.This thesis provides a new idea for high concentration trap doping of organic active layer.