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 ( η ed ) and charge transfer state dissociation efficiency ( η cd ). These spacers enhance interfacial band‐bending, boosting η cd with minimal η ed loss. The optimized ITO/HAT‐CN/TPD/SubPc/6PFB(4 nm)/C 60 /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.