Perfluoroarene-Based Interlayers Unlock High External Quantum Efficiency in Planar Heterojunction OPDs

Abstract

Suppressing dark current while enhancing photocurrent remains a key challenge in organic photodiodes (OPDs). Planar heterojunction (PHJ) OPDs offer low dark current and high phase stability but often suffer from low photocurrent. Here, we present perfluoroarene-based spacer layers-2PFB, 4PFB, and 6PFB-as a strategy to simultaneously improve exciton dissociation efficiency (eta ed) and charge transfer state dissociation efficiency (eta cd). These spacers enhance interfacial band-bending, boosting eta cd with minimal eta ed loss. The optimized ITO/HAT-CN/TPD/SubPc/6PFB(4 nm)/C60/Bphen/Al OPD achieves a peak external quantum efficiency (EQE) over 70%. The method is compatible with various donors when favorable Fermi level alignment is present. Furthermore, monolithic integration of 6PFB-based OPDs on CMOS readout circuits yielded a 77.9% increase in sensitivity, confirming their practical viability. This approach offers a generalizable, effective pathway to overcoming the EQE-photocurrent trade-off in PHJ OPDs, representing a significant advancement toward high-performance, commercially viable organic photodetectors.