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Vol. 18 (2026)

Enhancing π-Delocalization and Suppressing Traps via Doping in Electron Transport Materials for Efficient Semitransparent Organic Photovoltaics

https://doi.org/10.1007/s40820-026-02083-1
Yating Mo
College of Polymer Science and Engineering, State Key Laboratory of Advanced Polymer Materials, Sichuan University, 610065 Chengdu, People’s Republic of China
Jiayu Wang
College of Polymer Science and Engineering, State Key Laboratory of Advanced Polymer Materials, Sichuan University, 610065 Chengdu, People’s Republic of China
Hanjiao Chen
Analytic & Testing Center, Sichuan University, 610065 Chengdu, People’s Republic of China
Yufei Gong
Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, 100190 Beijing, People’s Republic of China
Jianglong Zhou
Key Laboratory of Green Chemistry & Technology, Ministry of Education, College of Chemistry, Sichuan University, 610065 Chengdu, People’s Republic of China
Junhao Lu
College of Polymer Science and Engineering, State Key Laboratory of Advanced Polymer Materials, Sichuan University, 610065 Chengdu, People’s Republic of China
Cenqi Yan
College of Polymer Science and Engineering, State Key Laboratory of Advanced Polymer Materials, Sichuan University, 610065 Chengdu, People’s Republic of China
Lei Meng
Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, 100190 Beijing, People’s Republic of China
Liang‑Wen Feng
Key Laboratory of Green Chemistry & Technology, Ministry of Education, College of Chemistry, Sichuan University, 610065 Chengdu, People’s Republic of China
Yongfang Li
Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, 100190 Beijing, People’s Republic of China
Pei Cheng
College of Polymer Science and Engineering, State Key Laboratory of Advanced Polymer Materials, Sichuan University, 610065 Chengdu, People’s Republic of China

Corresponding Author: Pei Cheng

chengpei@scu.edu.cn

Nano-Micro Letters, Vol. 18 (2026), Article Number: 247

Abstract

The ultrathin metal electrode in semitransparent organic photovoltaics (STOPVs) usually suffers from limited charge collection capability and conductivity and thus hinders the power conversion efficiency (PCE). Herein, a new strategy of enhancing the π-delocalization of electron transport layer (ETL) via lithium bis(trifluoromethanesulfonyl)imide doping is developed. The enhanced π-delocalization in ETL benefits sizeable intermolecular π–π overlap, prone to harvesting electrons and thereby improving charge collection range. Doping also improves the conductivity of both ETL and ultrathin silver electrode. Furthermore, the trap densities in ETL and STOPV devices are reduced after doping, contributing to suppressed recombination and higher PCE. Consequently, ETL doping maintains an average visible transmittance of ~ 30% while promotes the PCE of STOPVs from 13.0% to 14.3% and light utilization efficiency from 3.74% to 4.15%, which is among the highest values of optical structure-free STOPVs. This work provides a new insight of π-delocalization manipulation in ETL for efficient STOPVs.


Highlights:
1 High-performance semitransparent organic photovoltaics (STOPVs) with decreased electrical loss were fabricated via introducing lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to electron transport layer (ETL).
2 LiTFSI interacts with ETL material PDINN and enhanced π-delocalization in PDINN, which is beneficial to conductivity and thereby electron collection range.
3 LiTFSI-doped PDINN-based STOPVs show an improved power conversion efficiency of 14.3%, average visible transmittance of 29.0%, and light utilization energy of 4.15%, which is among the highest values of optical structure-free STOPVs.

Keywords

Semitransparent organic photovoltaics Interfacial engineering π-delocalization Surface traps Electrical loss
Mo, Yating, Jiayu Wang, Hanjiao Chen, Yufei Gong, Jianglong Zhou, Junhao Lu, Cenqi Yan, Lei Meng, Liang‑Wen Feng, Yongfang Li, and Pei Cheng. 2026. “Enhancing π-Delocalization and Suppressing Traps via Doping in Electron Transport Materials for Efficient Semitransparent Organic Photovoltaics”. Nano-Micro Letters 18 (February):247. https://doi.org/10.1007/s40820-026-02083-1.
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