Over 17.4% Efficiency of Layer‐by‐Layer All‐Polymer Solar Cells by Improving Exciton Utilization in Acceptor Layer

• Published in: Advanced functional materials Vol. 33; no. 28
• Main Authors: Xu, Wenjing, Zhang, Miao, Ma, Xiaoling, Zhu, Xixiang, Jeong, Sang Young, Woo, Han Young, Zhang, Jian, Du, Wenna, Wang, Jian, Liu, Xinfeng, Zhang, Fujun
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc 01.07.2023
• Subjects: all‐PSCs; Charge transport; Efficiency; Electrodes; Energy conversion efficiency; Energy gap; Energy transfer; exciton utilization; Excitons; layer‐by‐layer; Materials science; Photoluminescence; Photovoltaic cells; Polymers; Solar cells; Spin coating; Utilization
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202215204

Layer‐by‐layer all‐polymer solar cells (LbL all‐PSCs) are prepared with PM6 and PY‐IT by using sequential spin coating method. The exciton dissociation efficiency in acceptor layer near electrode is rather low due to the limited exciton diffuse distance and impossible energy transfer from narrow bandgap acceptor to wide bandgap donor. In this study, less PM6 is incorporated into PY‐IT layer to enhance exciton dissociation in PY‐IT layer near electrode. A power conversion efficiency (PCE) of 17.45% is achieved in the LbL all‐PSCs incorporating 10 wt% PM6 into PY‐IT layer, which is much larger than 16.04% PCE of PM6/PY‐IT‐based LbL all‐PSCs. Over 8% PCE enhancement can be realized by incorporating 10 wt% PM6 into PY‐IT layer, which is attributed to the enhanced exciton utilization efficiency in PY‐IT layers near electrode. The enhanced exciton utilization efficiency in PY‐IT layer can be confirmed from the quenched photoluminescence (PL) emission in PY‐IT:PM6 films. Meanwhile, charge transport in acceptor layers can be optimized by incorporating less PM6, as confirmed from the optimized molecular arrangement. This study indicates that the strategy of incorporating less donor into acceptor layer has great potential in fabricating efficient LbL all‐PSCs by improving exciton utilization efficiency in acceptor layer near electrode. There is a great challenge in improving exciton utilization efficiency on top of acceptor layer in layer‐by‐layer all‐polymer solar cells (LbL all‐PSCs) due to the limited exciton diffuse distance and impossible energy transfer from acceptor to donor. The exciton utilization efficiency in PY‐IT layers near electrode can be improved by incorporating appropriate PM6 in PY‐IT layer, resulting in the enhanced power conversion efficiencies from 16.04% to 17.45% in LbL all‐PSCs with 10 wt% PM6 in PY‐IT layer.