Morphology and carrier non-geminate recombination dynamics regulated by solvent additive in polymer/fullerene solar cells

Ming-Ming Huo; Rong Hu; Qing-Shan Zhang; Shaoting Chen; Xing Gao; Yi Zhang; Wei Yan; Yong Wang

doi:10.1039/d0ra03389h

Morphology and carrier non-geminate recombination dynamics regulated by solvent additive in polymer/fullerene solar cells

RSC Adv. 2020 Jun 17;10(39):23128-23135. doi: 10.1039/d0ra03389h. eCollection 2020 Jun 16.

Authors

Ming-Ming Huo¹, Rong Hu², Qing-Shan Zhang², Shaoting Chen¹, Xing Gao², Yi Zhang², Wei Yan¹, Yong Wang¹

Affiliations

¹ Laser Institute, Qilu University of Technology (Shandong Academy of Sciences) Qingdao Shandong 266100 China yongwang@sdlaser.cn mingminghuo@sdlaser.cn shaoting.chen@sdlaser.cn weiyan@sdlaser.cn.
² Research Institute for New Materials Technology, Chongqing University of Arts and Sciences Chongqing 402160 China hurong_82@cqwu.edu.cn 2584435203@qq.com 1345542490@qq.com 2803904178@qq.com.

Abstract

In this study, PBDTTT-E (based on benzo [1,2-b:4,5-b'] dithiophene (BDT) and thieno [3,4-b] thiophene (TT)) as a donor and fullerene derivative PC₇₁BM (phenyl-C₇₁-butyric acid methyl ester) as an acceptor with and without 1,8-diiodooctane (DIO)-treated copolymer solar cells were investigated. The device based on PBDTTT-E with treated DIO showed remarkably high current density (J _sc), fill factor (FF) and similar open-circuit voltage (V _oc). Charge carrier lifetime (τ _n ), density (n) and non-geminate recombination rate (k _rec) in the photoactive layers were measured by employing transient photovoltage (TPV) and charge extraction (CE) techniques. Based on k _rec and n, J-V curves were reconstructed. The DIO optimized the morphology of the active layer and its PBDTTT-E:PC₇₁BM interfaces were increased. Therefore, compared to the device without the treated DIO, the device with the treated DIO showed larger electron mobility, longer carrier lifetime (τ _n ) and lower non-geminate recombination rate (k _rec), which enhances the carrier transport and restrains the non-geminate recombination, realizing the higher J _sc and FF. In addition, that the DIO-treated devices can weaken the role of other factors (such as field dependent geminate recombination) in limiting device performance. The results provide some hints of improved device performance upon DIO as an additive in the D-A type polymer/fullerene solar cells.