Enhanced photovoltaic performance for quinoxaline‐based polymeric donor via backbone engineering for non‐fullerene organic solar cells

Abstract

Herein, we demonstrate a facile technique for transforming a low‐energy‐converting quinoxaline‐based polymer into an efficient polymeric donor for non‐fullerene acceptor‐based organic solar cells (NFA‐OSCs). Alternating copolymers, namely P(BDTSi‐DTfQ), incorporating electron‐rich 4,8‐bis(triisopropylsilylethynyl)‐benzo[1,2‐b:4,5‐′]dithiophene (BDTSi) and electron‐deficient 2,3‐didodecyl‐6‐fluoro‐5,8‐di(thiophen‐2‐yl)quinoxaline (DTfQ) units were synthesized. The properties of P(BDTSi‐DTfQ) were thoroughly studied and briefly compared to those of the reported polymers, namely P(BDTSi‐DTffQ), made up of BDTSi and 2,3‐didodecyl‐6,7‐difluoro‐5,8‐di(thiophen‐2‐yl)quinoxaline (DTffQ) units. Polymer P(BDTSi‐DTfQ) exhibited a lower bandgap (Eg) and higher highest occupied and lowest unoccupied energy levels (HOMO and LUMO) than P(BDTSi‐DTffQ). The estimated Eg and HOMO/LUMO for P(BDTSi‐DTfQ) were 1.90 eV and −5.46 eV/−3.56 eV, respectively, and for P(BDTSi‐DTffQ) the same were 1.94 eV and −5.58 eV/−3.64 eV, respectively. Interestingly, the NFA‐OSCs made from P(BDTSi‐DTfQ) as the donor and NFA, namely ITIC, as the acceptor, gave a power conversion efficiency (PCE) of 3.68%, which is much higher than the PCE obtained (⁓0.75%) for the OSCs prepared by using the P(BDTSi‐DTffQ):ITIC blend. Noticeably, the energy levels of P(BDTSi‐DTfQ) were found to be favorable for efficient charge separation when it was blended with ITIC. This blend not only allowed a better charge separation at the donor/acceptor interfaces but also significantly lowered bimolecular recombination. The overall effect was to provide a higher PCE. However, P(BDTSi‐DTffQ) showed mismatched energy levels with ITIC resulting in a higher bimolecular recombination and lower PCE.

Bifunctional Urea–Polyethyleneimine‐Mediated Surface Engineering in SnO2 Electron‐Transport Layer for Efficient and Stable Organic Solar Cells

“…In response, electron-transport layers (ETLs) have been developed and optimized to mitigate the energy barrier with Y-series NFAs, improving the charge-carrier transfer. [6][7][8][9][10] Currently, zinc oxide (ZnO) is the predominant choice for ETL materials for inverted OSCs because of its distinctive characteristics, including energy levels compatible with Y-series NFAs. [11][12][13][14] However, the well-known photostability issues of ZnO, which cause the degradation of Y-series NFAs through photocatalytic reactions under UV light, led us to investigate alternative ETL materials possessing both durability and optimized energy-level alignment with Y-series NFAs.…”

Molecular structural descriptor‐assisted machine learning for organic photovoltaics with perylenediimide acceptors

“…In addition to the development of the process for BHJ morphological optimization, the series of steps for synthesizing new materials, testing numerous material combinations, and fine-tuning the chemical composition ratios require numerous trials and errors. [9][10][11][12][13][14] Therefore, machine learning (ML) approaches to screen numerous BHJ combinations in a short time and with little effort, based on a comprehensive understanding of the potential of OPV materials, have attracted considerable attention. 15,16 State-of-the-art OPV ML models achieved superior accuracy with a variety of input data types and algorithms.…”