# Octupole moment driven free charge generation in partially chlorinated subphthalocyanine for planar heterojunction organic photodetectors

## TL;DR

This paper shows that chlorinated subphthalocyanine can generate free charges efficiently in organic photodetectors due to its high octupole moment, leading to high performance.

## Contribution

The study introduces the role of high octupole moment in enabling direct charge generation in single-component organic photodetectors.

## Key findings

- Chlorinated subphthalocyanine generates photocurrent through direct charge generation, not exciton separation.
- A 50 nm thick layer achieves detectivity near 10^13 Jones with low dark current.
- Increasing layer thickness reduces trap density and improves response time.

## Abstract

In this study, high-performance organic photodetectors are presented which utilize a pristine chlorinated subphthalocyanine photoactive layer. Optical and optoelectronic analyses indicate that the device photocurrent is primarily generated through direct charge generation within the chlorinated subphthalocyanine layer, rather than exciton separation at layer interfaces. Molecular modelling suggests that this direct charge generation is facilitated by chlorinated subphthalocyanine high octupole moment (−80 DÅ2), which generates a 200 meV shift in molecular energetics. Increasing the thickness of chlorinated subphthalocyanine leads to faster response time, correlated with a decrease in trap density. Notably, photodetectors with a 50 nm thick chlorinated subphthalocyanine photoactive layer exhibit detectivities approaching 1013 Jones, with a dark current below 10−7 A cm−2 up to −5 V. Based on these findings, we conclude that high octupole moment molecular semiconductors are promising materials for high-performance organic photodetectors employing single-component photoactive layer.

Rana et al. report octupole moment-driven local energetic offsets in Cl6-SubPc, which leads to direct free charge generation when serves as the electron acceptor layer in planar heterojunction organic photodetectors, exhibiting significant potential for single- and multi-layer optoelectronic devices.