Conjugated Mesopolymer Achieving 15% Efficiency Single‐Junction Organic Solar Cells

Abstract

The high‐performance organic solar cells (OSCs) tend to choose the polymers with high molecular weight as donors, which easily produce good crystallinity to facilitate intermolecular charge transfer. However, these polymers usually accompanied by the low solubility and synthetic difficulty, increasing batch‐to‐batch variations. The proposal of conjugated mesopolymers (molar mass (Mn) in 1–10 kDa) can overcome these problems. Herein, a new mesopolymer, MePBDFClH as donor material is designed and synthesized, and firstly applied in OSCs. As a comparison, other lower molecular weight mesopolymer of MePBDFClL and higher molecular weight polymer of PBDFCl with same structure are also prepared and investigated. Because of its appropriate phase separation and miscibility in the blend film, the MePBDFClH exhibits the highest power conversion efficiency (PCE) of 15.06% among the three materials. Meanwhile, the champion PCE is a new record for benzo[1,2‐b:4,5‐b′]difuran‐based photovoltaic materials. Importantly, comparing to the pronounced PCE decrease of polymer PBDFCl by about 12%, a slightly PCE difference for mespolymer MePBDFClL is only less than 5%, reducing the batch‐to‐batch variation. This work not only suggests that the benzo[1,2‐b:4,5‐b′]difuran unit is a promising electron‐donating core but also shows that the mesopolymers have great potentials to produce the low‐differentiated and high‐performance organic photovoltaic materials.

High Performance and Stable Organic Solar Cells Fabricated by Y-Series Small Molecular Materials as the Interfacial Modified Layer

“…The slope β of the V OC versus P light shows the monomolecular recombination of the OSCs and when the slope β = kT / e ( k is Boltzmann’s constant, T is the absolute temperature, and e is the elementary charge), it indicates minimal monomolecular recombination. The slope β values of the control, Y6-modified, BTP-eC9-modified, and L8-BO-modified devices are 1.333 kT / e , 1.021 kT / e , 1.114 kT / e , and 1.052 kT / e , respectively, which indicates that the monomolecular recombination is also hindered by the optimization of the IML . Moreover, Figure c shows that the photocurrent density versus effective voltage ( J ph – V eff ) curves of the different devices were measured to investigate the exciton dissociation probability in the active layer.…”

“…The slope β values of the control, Y6-modified, BTP-eC9-modified, and L8-BO-modified devices are 1.333 kT/e, 1.021 kT/e, 1.114 kT/e, and 1.052 kT/e, respectively, which indicates that the monomolecular recombination is also hindered by the optimization of the IML. 41 Moreover, Figure 3c shows that the photocurrent density versus effective voltage (J ph −V eff ) curves of the different devices were measured to investigate the exciton dissociation probability in the active layer. J ph is the value of the difference between the illuminated current density (J L ) and the dark current density (J D ).…”

A Benzo[1,2‐b:4,5‐b′]Difuran Based Donor Polymer Achieving High‐Performance (>17%) Single‐Junction Organic Solar Cells with a Fill Factor of 80.4%

“…[42][43][44] Besides, due to the smaller size of furan than thiophene, the steric hindrance in the BDF-based polymer backbones is usually weaker than that in the BDT-based ones, leading to tighter molecular packing and thus higher hole mobility in the bulk-heterojunction. [45][46][47] In addition, the furan units are more environmentalfriendly due to its biodegradability and bio-renewability, which may be more suitable for scale-up production. [48][49][50] Therefore, it is promising to design novel polymer donors based on BDF units and it is also important to choose proper NFAs to match with them for highly efficient OSCs.…”

Recent advances in benzodifuran based photovoltaic materials

“…Nevertheless, a small molecular weight is difficult to crystallize, hindering high efficiency. Recently, Zheng et al 24 utilized the advantage of stacking for BDF-based materials, synthesizing a mesopolymer and achieving a PCE of over 15%. Thus, BDF-based materials have facilitated a rapid increase in photovoltaic performance from 5% to 16% 75 in 10 years (Fig.…”