Utilizing Benzotriazole and Indacenodithiophene Units to Construct Both Polymeric Donor and Small Molecular Acceptors to Realize Organic Solar Cells With High Open-Circuit Voltages Beyond 1.2 V

Abstract

Devolopment of organic solar cells with high open-circuit voltage (VOC) and power conversion efficiency (PCE) simutaniously plays a significant role, but there is no guideline how to choose the suitable photovoltaic material combinations. In our previous work, we developed “the Same-Acceptor-Strategy” (SAS), by utilizing the same electron-accepting segment to construct both polymeric donor and small molecular acceptor. In this study, we further expend SAS to use both the same electron-accepting and electron-donating units to design the material combination. The p-type polymer of PIDT-DTffBTA is designed by inserting conjugated bridge between indacenodithiophene (IDT) and fluorinated benzotriazole (BTA), while the n-type small molecules of BTAx (x = 1, 2, 3) are obtained by introducing different end-capped groups to BTA-IDT-BTA backbone. PIDT-DTffBTA: BTAx (x = 1–3) based photovolatic devices can realize high VOC of 1.21–1.37 V with the very small voltage loss (0.55–0.60 V), while only the PIDT-DTffBTA: BTA3 based device possesses the enough driving force for efficient hole and electron transfer and yields the optimal PCE of 5.67%, which is among the highest value for organic solar cells (OSCs) with a VOC beyond 1.20 V reported so far. Our results provide a simple and effective method to obtain fullerene-free OSCs with a high VOC and PCE.

Benzotriazole-Based Acceptor and Donors, Coupled with Chlorination, Achieve a High VOC of 1.24 V and an Efficiency of 10.5% in Fullerene-Free Organic Solar Cells

“…As reported in our previous work, utilizing the same acceptor unit (A) to build both p-type and n-type photovoltaic materials, named “Same-A-Strategy” or “Same-Acceptor-Strategy” (SAS), could facilitate to decrease the Δ E LUMO and Δ E HOMO to some extent and thus improve the V OC . , Herein, the benzotriazole (BTA) is chosen as the conjunct A unit for the application in SAS. As shown in Scheme , BTA3 with a high-lying LUMO energy level is chosen as the non-fullerene acceptor (NFA), and a D-π-A type polymer ( J52 ) containing fluorinated BTA unit is chosen as the p-type material.…”

Planar Benzofuran Inside-Fused Perylenediimide Dimers for High VOC Fullerene-Free Organic Solar Cells

“…24 Until recent successful exploration of tailoring methods, various PDI molecules exhibiting good stability and high electron mobility have become an exciting and active research area within the field of fullerene-free OSCs. 25,26 The modified position at the bay or imide position of the perylene core and the nature of the attached substituents strongly impact their solubility, electronic structure, and absorption capability. According to the number of parent PDI units, PDI-based small molecules can be divided into single-, double-, and multi-PDIs.…”

“…The major reason is that the intense intermolecular interactions between the rigid fused PDI molecules induce poor controllability of phase separation size in the blend system, resulting in serious charge recombination . Until recent successful exploration of tailoring methods, various PDI molecules exhibiting good stability and high electron mobility have become an exciting and active research area within the field of fullerene-free OSCs. , …”

Development of n-Type Porphyrin Acceptors for Panchromatic Light-Harvesting Fullerene-Free Organic Solar Cells

“…In the 2010s, new types of OSCs replaced the fullerenes with strong light-harvesting organic non-fullerene acceptors (NFAs). The active layer was composed of organic donors and NFAs, called fullerene-free OSCs (Cheng et al, 2017 ; Lin et al, 2017 ; Tang et al, 2018 ; Yan et al, 2018 ). Due to the strong absorption of both NFAs and organic donors in the visible area, their complementary absorption is important to achieve panchromatic photon-to-current conversion in the active layer.…”