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Nano Lett. 2018 Sep 12;18(9):5805-5811. doi: 10.1021/acs.nanolett.8b02452. Epub 2018 Aug 10.

High Mobility Indium Oxide Electron Transport Layer for an Efficient Charge Extraction and Optimized Nanomorphology in Organic Photovoltaics.

Huang W1,2, Zhu B1,2, Chang SY1,2, Zhu S1,2, Cheng P1,2, Hsieh YT1,2, Meng L1,2, Wang R1,2, Wang C1,2, Zhu C3, McNeill C4, Wang M5, Yang Y1,2.

Author information

1
Department of Materials Science and Engineering , University of California , Los Angeles , California 90095 , United States.
2
California NanoSystems Institute , University of California , Los Angeles , California 90095 , United States.
3
Advanced Light Source , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States.
4
Department of Materials Science and Engineering , Monash University , Clayton , Victoria 3800 , Australia.
5
Wuhan National Laboratory for Optoelectronics , Huazhong University of Science and Technology , Wuhan 430070 , People's Republic of China.

Abstract

The electron transport layer (ETL) plays an important role in determining the device efficiency of organic solar cells (OSCs). A rational design of an ETL for OSCs targets high charge extraction and induction of an optimized active layer morphology. In this Letter, a high mobility In2O3 synthesized via a solution-processed combustion reaction is successfully used as a universal ETL in an organic photovoltaic device. With the modification of a thin layer of polyethylenimine ethoxylated (PEIE), a device based on crystalline In2O3 outperforms its counterpart, ZnO, in both PBDTTT-EFT-based fullerene and nonfullerene systems. As ZnO is replaced by In2O3, the average efficiency increases from 9.5% to 10.5% for PBDTTT-EFT-PC71BM fullerene-based organic solar cells and also increases from 10.8% to 11.5% for PBDTTT-EFT-IEICO-4F nonfullerene-based organic solar cells, respectively. Morphological studies have unraveled the fact that the crystalline In2O3 ETL with highly aligned nanocrystallites has induced the crystallization of polymer into a preferential molecular packing that favors the charge transport across an active layer. From the photophysical study, it is found that charge extraction in the crystalline In2O3 device is significantly faster than in the ZnO device due to the higher mobility of In2O3 and optimized nanomorphology of the active layer.

KEYWORDS:

Organic solar cells; charge extraction; electron transport layer; indium oxide; morphology

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