In-situ understanding on the formation of fibrillar morphology in green solvent processed all-polymer solar cells

Ruijie Ma; Hongxiang Li; Top Archie Dela Peña; Heng Wang; Cenqi Yan; Pei Cheng; Jiaying Wu; Gang Li

doi:10.1093/nsr/nwae384

In-situ understanding on the formation of fibrillar morphology in green solvent processed all-polymer solar cells

Natl Sci Rev. 2024 Nov 4;11(12):nwae384. doi: 10.1093/nsr/nwae384. eCollection 2024 Dec.

Authors

Ruijie Ma¹, Hongxiang Li², Top Archie Dela Peña³, Heng Wang², Cenqi Yan², Pei Cheng², Jiaying Wu³, Gang Li¹

Affiliations

¹ Department of Electrical and Electronic Engineering, Research Institute for Smart Energy (RISE), Photonic Research Institute (PRI), The Hong Kong Polytechnic University, Hong Kong 999077, China.
² College of Polymer Science and Engineering, State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu 610040, China.
³ Function Hub, Advanced Materials Thrust, The Hong Kong University of Science and Technology, Guangzhou 511400, China.

Abstract

Solid additive engineering has been intensively explored on morphology tuning for highly efficient all-polymer solar cells (all-PSCs), a promising photovoltaic technology towards multi-scenario application. Although the nano-fibrillar network of the active layer induced by additive treatment is confirmed as the key factor for power conversion efficiency (PCE) of all-PSCs, its formation mechanism is not clearly revealed, for lack of precise and convincing real-time observation of crystallization and phase separation during the liquid-to-solid transition process of spin-coating. Herein we report an in-situ grazing incidence wide-angle/small-angle X-ray scattering (GIWAXS/GISAXS) screening that reveals the fact that naphthalene derived solid additives can suppress the aggregation of the polymer acceptor (PY-IT) at the beginning stage of spin coating, which provides sufficient time and space for the polymer donor (PM6) to form the fibril structure. Moreover, guided by this knowledge, a ternary all-polymer system is proposed, which achieves cutting-edge level PCEs for both small-area (0.04 cm²) (also decent operational stability) and large-area (1 cm²) devices.

Keywords: all-polymer solar cells; in-situ morphology screening; naphthalene-based solid additives; phase segregation.