Chirality transfer from chiral perovskite to molecular dopants via charge transfer states

TL;DR

This study demonstrates that doping chiral perovskites with F4TCNQ enhances electrical conductivity and introduces visible light absorption with circular dichroism, enabling selective circularly polarized light detection.

Contribution

It reveals a universal method to transfer chirality to molecular dopants via charge transfer states, broadening optical absorption and improving conductivity in chiral perovskites.

Findings

Doping improves electrical conductivity and introduces visible light absorption.

Charge transfer states exhibit strong circular dichroism, indicating chirality transfer.

Doped perovskite photodetectors can selectively detect circularly polarized light.

Abstract

Chiral perovskites are emerging semiconducting materials with broken symmetry that can selectively absorb and emit circularly polarized light. However, most of the chiral perovskites are typically low-dimensional structures with limited electrical conductivity and their light absorption occurs in the UV region. In this work, we find doping 2,3,5,6-Tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) in the chiral perovskite matrix can improve the electrical conductivity with an addition of visible light absorption through the emerging charge-transfer electronic states. The new absorption feature exhibits strong circular dichroism adapted from the chiral matrix, which is indicative of a chirality transfer from the host to the guest via an electronic coupling. The charge transfer state is validated by transient absorption spectroscopy and theory modeling. Quantum-chemical modeling identifies a strong wave function overlap between an electron and a hole of the guest-host in a closely packed crystal configuration forming the charge-transfer absorption state. We then integrate the doped chiral perovskite film in photodetectors and demonstrate a selective detection of circularly polarized light both in the UV and visible range. Our results suggest a universal approach of introducing visible photo absorption states to the chiral matrix to broaden the optical active range and enhance the conductivity.