Sub-5 nm single crystalline organic p\u2013n heterojunctions

Mingchao Xiao,Yanjun Shi,Lang Jiang,Chuan Liu,Yuanyuan Hu,Wenping Hu,Yuanping Yi,Dong Wang,Shuai Wang,Guangchao Han,Zhengxu Cai,Xike Gao,Zitong Liu,Yunqi Liu,Ji Liu,Jie Liu,Xi Zhang,Chunlei Li,Henning Sirringhaus

doi:10.1038/s41467-021-23066-3

Abstract

The cornerstones of emerging high-performance organic photovoltaic devices are bulk heterojunctions, which usually contain both structure disorders and bicontinuous interpenetrating grain boundaries with interfacial defects. This feature complicates fundamental understanding of their working mechanism. Highly-ordered crystalline organic p–n heterojunctions with well-defined interface and tailored layer thickness, are highly desirable to understand the nature of organic heterojunctions. However, direct growth of such a crystalline organic p–n heterojunction remains a huge challenge. In this work, we report a design rationale to fabricate monolayer molecular crystals based p–n heterojunctions. In an organic field-effect transistor configuration, we achieved a well-balanced ambipolar charge transport, comparable to single component monolayer molecular crystals devices, demonstrating the high-quality interface in the heterojunctions. In an organic solar cell device based on the p–n junction, we show the device exhibits gate-tunable open-circuit voltage up to 1.04 V, a record-high value in organic single crystalline photovoltaics.

Highlights

The cornerstones of emerging high-performance organic photovoltaic devices are bulk heterojunctions, which usually contain both structure disorders and bicontinuous interpenetrating grain boundaries with interfacial defects
Achieving highly ordered crystalline p–n heterojunctions with atomically well-defined interface at monolayer thickness limit, is a powerful strategy for studying exciton physics without the limitations imposed by exciton diffusion lengths, as well as an efficient way to reveal the fundamental mechanisms in organic optoelectronic devices
We proposed a controllable two-dimensional space phase separation method, and monolayer molecule crystals (MMCs) are obtained from a solution mixture of poly(methyl methacrylate) (PMMA) and 2,6-bis(4-hexylphenyl)anthracene (C6DPA, Fig. 1a)[29]

Summary

Introduction

The cornerstones of emerging high-performance organic photovoltaic devices are bulk heterojunctions, which usually contain both structure disorders and bicontinuous interpenetrating grain boundaries with interfacial defects This feature complicates fundamental understanding of their working mechanism. On the other hand, when thickness of the p–n junction is downscaled to the molecular level, excitons generated by photon absorption would be present directly at the p–n junction interface with low loss, and probably completely dissociate into free holes and electrons It has been experimentally validated higher device performance could be obtained when size of micro-phase domain decreased[18,19], and the optimized micro-phase domain size might vary from case to case depending on the materials used. Achieving highly ordered crystalline p–n heterojunctions with atomically well-defined interface at monolayer thickness limit, is a powerful strategy for studying exciton physics without the limitations imposed by exciton diffusion lengths, as well as an efficient way to reveal the fundamental mechanisms in organic optoelectronic devices. The direct growth of such thin single-crystalline p–n heterojunctions remains a huge challenge, which significantly limits their applications in organic optoelectronic devices

Methods

Results

Conclusion