Realizing photomultiplication-type organic photodetectors based on C_(60)-doped bulk heterojunction structure at low bias

Photomultiplication(PM) structure has been widely employed to improve the optoelectronic performance of organic photodetectors(OPDs). However, most PM-type OPDs require a high negative operating voltage or complex fabrication. For obtaining high-efficiency OPDs with low voltage and easy process, here the bulk heterojunction(BHJ) structure of high exciton dissociation efficiency combined with the method of trap-assisted PM are applied to the OPDs.In this paper, we investigate the operating mechanism of OPDs based on poly(3-hexylthiophene)(P3 HT):(phenyl-C61-butyric-acid-methyl-ester)(PC61 BM), and poly-{[4,8-bis[(2-ethylhexyl)oxy]-benzo[1,2-b:4,5-b]dithiophene-2,6-diyl]-alt-[3-fluore-2-(octyloxy)carbonyl-thieno[3,4-b]thiophene-4,6-diyl]}(PBDT-TT-F):PC_(61)BM doped with C_(60) as active layer.Furthermore, the influence of C_(60) concentration on the optoelectronic performances is also discussed. With 1.6 wt.% C_(60)added, the P3 HT:PC_(61)BM:C_(60) OPD exhibits a 327.5% external quantum efficiency, a 1.21 A·W^(-1) responsivity, and a4.22 x 1012 Jones normalized detectivity at-1 V under 460 nm(0.21 mW·cm^(-2)) illumination. The experimental results show that the effective electron traps can be formed by doping a small weight of C_(60) into BHJ active layer. Thus the PM-type OPDs can be realized, which benefits from the cathode hole tunneling injection assisted by the trapped electrons in C_(60) near the A1 side. The efficiency of PM is related to the C_(60) concentration. The present study provides theoretical basis and method for the design of highly sensitive OPDs with low operating voltage and facile fabrication.

Photomultiplication type all-polymer photodetectors with single carrier transport property

Photomultiplication(PM)type all-polymer photodetectors(all-PPDs)are first demonstrated with the sandwich structure of ITO/PEDOT:PSS/PBDB-T:PZ1(100:x,wt/wt)/Al.The optimal PM type all-PPDs with PBDB-T:PZ1(100:3,wt/wt)as active layers exhibit external quantum efficiency(EQE)of>100%in the spectral range from 310 to 790 nm.Under 675 nm light illumination,the champion EQE value arrives to 1,470%at-20 V bias and the specific detectivity approaches 1×10^12 Jones at-10 V bias.The PM phenomenon in all-PPDs results from hole tunneling injection assisted by interfacial band bending induced by trapped electrons in PZ1 near Al electrode.The EQE values of optimal PM type all-PPDs still remained over 90%of the original value after 60 d of the storage in a high-purity nitrogen-filled glove box.

Broadband photomultiplication-type polymer photodetectors and its application in light-controlled circuit

Photomultiplication-type polymer photodetectors(PM-PPDs)were achieved with polymer P3HT as donor and PY3Se-1V as acceptor based on structure of ITO/PEDOT:PSS/active layer/Al.The optimal weight ratio of P3HT to PY3Se-1V is about 100:3.Amounts of isolated electron traps are formed with PY3Se-1V surrounded by P3HT due to rather less content of PY3Se-1V in active layers and about 0.94 e V energy offset between the lowest unoccupied molecular orbitals(LUMO)of P3HT and PY3Se-1V.The optimal PM-PPDs exhibit broad spectral response from 350 to 950 nm and external quantum efficiency(EQE)values of68,200%at 360 nm,26,400%at 630 nm and 19,500%at 850 nm under-15 V bias.The working mechanism of PM-PPDs is attributed to the interfacial trap-assisted hole tunneling injection from external circuit.The performance of PM-PPDs can be further improved by incorporating appropriate PMBBDT with high hole mobility as the third component.The EQE values of optimal ternary PM-PPDs are increased to 105,000%at 360 nm,40,000%at 630 nm and 31,800%at 850 nm under-15 V bias,benefiting from the enhanced hole transport in ternary active layers.The optimal ternary PM-PPDs were successfully applied in a light-controlled circuit to turn on or turn off light emitting diode(LED).

Highly sensitive polymer photodetectors with a wide spectral response range

A series of highly sensitive polymer photodetectors（PPDs） was fabricated with P3HT100-x：PBDT-TS1x：PC71BM1 as the active layers, where x represents the PBDT-TS1 doping weight ratio in donors. The response range of PPDs can cover from the UV to near-infrared regions by adjusting the PBDT-TS1 doping weight ratio. The best external quantum efficiency（EQE） values of ternary PPDs with P3HT：PBDT-TS1：PC（71）BM（50：50：1 wt/wt/wt） as the active layers reach 830%, 720%,and 330% under 390-, 625-, and 760-nm light illumination and-10 V bias, respectively. The large EQE values indicate that the photodetectors utilise photomultiplication（PM）. The working mechanism of PM-type PPDs can be attributed to interfacial trap-assisted hole tunnelling injection from the external circuit under light illumination. The calculated optical field and photogenerated electron volume density in the active layers can well explain the EQE spectral shape as a function of the PBDT-TS1 doping weight ratio in donors.