High‐Performance Additive‐/Post‐Treatment‐Free Nonfullerene Polymer Solar Cells via Tuning Molecular Weight of Conjugated Polymers

Abstract

In recent years, rapid advances are achieved in polymer solar cells (PSCs) using nonfullerene small molecular acceptors. However, no research disclosing the influence of molecular weight (M ) of conjugated polymer on the nonfullerene device performance is reported. In this work, a series of polymers with different M s are synthesized to systematically investigate the connection between M and performance of nonfullerene devices for the first time. It is found that the device performance improves substantially as the M increases from 12 to 38 kDa and a power conversion efficiency (PCE) as high as 10.5% is realized. It has to be noted this PCE is achieved without using any additives and post-treatments, which is among the top efficiencies of additive- and post-treatment-free PSCs. Most importantly, the variation trend of the optimal active layer thickness and morphology is significantly different from the device with fullerene as acceptor. The findings clarify the effect of M on the performance of nonfullerene PSCs, which would benefit further efficiency improvement of nonfullerene PSCs.

Miscibility Tuning for Optimizing Phase Separation and Vertical Distribution toward Highly Efficient Organic Solar Cells

“…It has been recognized as a great promising substitute for silicon‐based photovoltaic with advantages of light weight, inexpensive cost, and large‐area flexible preparation with roll‐to‐roll (R2R) process. Besides understanding the internal mechanism of binary OSCs deeply, more and more efforts were paid to improve the performance of OSCs via tuning absorption and energy level of novel donor and acceptor materials, optimizing processing methods, interfacial engineering, and innovative device architectures …”

Effect of polymer molecular weight on J51 based organic solar cells

“…By comparing the device performance parameters, it is found that the V OC value slightly increases from 720 mV (J51-8kDa) to 753 mV (J51-36kDa), while the J SC and FF prominently increase from 5.42 to 12.18 mA cm À2 and 39.89% to 65.06%, respectively, because of the higher molar mass fractions, the higher charge mobility. 40,41 The surface morphology of optimal J51:PC 71 BM blends on ZnO-coated ITO was examined via atomic force microscopy (AFM) and measured in tapping mode (as shown in Fig. 4).…”

“…[21][22][23][24] Molecular weight is one of the most important parameter for polymer donors because molecular weight directly inuences optical-electricity property, solubility and the morphology of the active layer. [25][26][27][28][29][30][31] Relatively little efforts have been made to reveal how polymer molecular weight affects the device performance in OSCs, as it is difficult to control the polymer molecular weight well during the synthesis. With the increase of PBTIBDTT-S' M n from 12 to 38 kDa, the PCEs of PBTIBDTT-S:PC 71 BM devices gradually increased due to the large improvement in J sc and slight enhancement in FF.…”

A Wide‐Bandgap Conjugated Polymer Based on Quinoxalino[6,5‐f ]quinoxaline for Fullerene and Non‐Fullerene Polymer Solar Cells

“…This is different from the trend observed from fullerene‐based solar cells. The distinct molecular weight effects of polymer donors for different acceptors demonstrated in this paper will benefit the understanding of structure–property relationship and further development of new conjugated polymers for high efficiency PSCs 12b,30…”