Alkyl‐Chain Branching of Non‐Fullerene Acceptors Flanking Conjugated Side Groups toward Highly Efficient Organic Solar Cells

Abstract

Side‐chain modifications of non‐fullerene acceptors (NFAs) are essential for harvesting their full potential in organic solar cells (OSC). Here, an effective alkyl‐chain‐branching approach of the Y‐series NFAs flanking meta‐substituted phenyl side groups at the outer positions is demonstrated. Compared to BTP‐4F‐PC6 with linear m‐hexylphenyl chains, two new acceptors named BTP‐4F‐P2EH and BTP‐4F‐P3EH are developed with bulkier alkyl chains branched at the β and γ positions, respectively. These branched chains result in altered molecular packing of the NFAs and afford higher open‐circuit voltage of the devices. Despite the blue‐shifted absorption of the branched‐chain NFAs, their blends with PBDB‐T‐2F enable improved short‐circuit current density for the corresponding devices owing to the more suitable phase separation and better exciton dissociation. Consequently, the OSCs based on BTP‐4F‐P2EH and BTP‐4F‐P3EH yield enhanced device performance of 18.22% and 17.57%, respectively, outperforming the BTP‐4F‐PC6‐based ones (17.22%). These results highlight that the side‐chain branching design of NFAs has great potential in optimizing molecular properties and promoting photovoltaic performance.

Low-cost synthesis of small molecule acceptors makes polymer solar cells commercially viable

“…Y6-CHO was purchased from hyper. Inc. F-IC, F-ID, Cl-ID were purchased from SunTech Inc. ID and BZ were purchased from Bide Pharmatech Ltd. BTP-CHO, eC9-CHO, L8-CHO and Y5-CHO were synthesized according to the method of reference 47 . 5-Br-IC and 6-Br-IC were synthesized according to the method of references 48 , 49 .…”

Isogenous Asymmetric–Symmetric Acceptors Enable Efficient Ternary Organic Solar Cells with Thin and 300 nm Thick Active Layers Simultaneously

“…The effect of the ternary strategy on morphological modulation has been proved in different types of OSCs, which generally requires that the third component possesses advisable compatibility, solubility, and crystallinity with the host matrix. [25][26][27][28] The well-developed morphology contributes to accelerating charge generation and extraction, resulting in elevated J SC and fill factor (FF). According to the above advantages, the ternary strategy should be a viable route to relieve the disease of sensitive performance to active layer thickness for OSCs.…”

Ferroelectric Polymer Drives Performance Enhancement of Non‐fullerene Organic Solar Cells

“…Organic solar cells (OSCs) have attracted more and more attention due to their low cost, light weight, flexible and solution-processable properties. [1][2][3][4][5][6][7] Especially in recent years, OSCs based on bulk heterojunction (BHJ) have developed rapidly with the appearance of non-fullerene acceptors (NFAs), and a break-through power conversion efficiency (PCE) of over 18 % has been obtained for the single-junction devices. [8][9][10][11] The high efficiency of the OSCs mainly originates from the good light harvesting, efficient charge separation, transport and collection of the photocarriers.…”