High‐Performance Binary All‐Polymer Solar Cells with Efficiency Over 18.3% Enabled by Tuning Phase Transition Kinetics

Abstract

All‐polymer solar cells (All‐PSCs) are considered to be the most promising candidates for realizing efficient and stable organic solar cells (OSCs). However, the challenge of controlling morphology has hindered the performance of All‐PSCs. Compared to small molecule acceptors, polymer acceptors play a more crucial role in obtaining an ideal morphology for All‐PSCs. The molecular weight of polymer acceptors is one of the key factors determining the morphological and mechanical properties as well as the interactions with donors. Herein, by using a monomer of PYIT (PYIT1) and PYITs with low (PYIT2) and high (PYIT3) molecular weights, the impact of molecular weight of the polymer acceptor is systematically investigated on the phase transition process, morphological, and photovoltaic properties. It is found that tuning the molecular weight effectively regulates the phase transition process of the polymer acceptor and its interaction with the polymer donor. This induces significant effects on the aggregation behaviors of the polymers. Appropriate molecular weight polymer acceptors can facilitate favorable phase separation morphology. With PBQx‐Cl as the donor and PYIT2 as acceptor, a high‐performance binary All‐PSC is achieved with an efficiency of 18.39%. This study provides deep insights into the performance enhancement of All‐PSCs through rational polymer acceptor design.

Ternary polythiophene enables over 17% efficiency organic solar cells

“…PTVT-T:BTP-eC9 transport to electrodes. 36 In addition, to further assess the charge carrier transport abilities in the PT:BTP-eC9 blend lms, the space charge limited current (SCLC) method was employed to determine the hole (m h ) and electron (m e ) mobilities of the devices. As shown in Fig.…”

“…The shortest charge carrier extraction time and the longest τ of the PT-CN:BTP-eC9 based device suppress the charge carrier recombination and facilitate charge carriers to transport to electrodes. 36 In addition, to further assess the charge carrier transport abilities in the PT:BTP-eC9 blend films, the space charge limited current (SCLC) method was employed to determine the hole ( μ h ) and electron ( μ e ) mobilities of the devices. As shown in Fig.…”

Single-component organic solar cells—Perspective on the importance of chemical precision in conjugated block copolymers

“…The resulting material (PM6- b -PYIT) ( Figure 1D ) yielded the most efficient CBC-based SC-OSCs to date (14.9% PCE). In terms of peak efficiency, state-of-the-art binary polymer:NFA (>19%) (Liu K. et al, 2023 ; Wang et al, 2023 ) and all-polymer OSCs (>18%) (Bi et al, 2023 ) still outperform SC-OSCs. However, CBC-based solar cells are quickly catching up and show untapped potential (Li et al, 2021 ; Wu et al, 2021 , 2022 ; Cheng et al, 2023 ; Zheng et al, 2023 ).…”

“…This approach is thus very attractive for CBC synthesis, in particular since PM6 (or a derivative thereof) is applied as the D part for some of the best-performing CBCs to date. Bi et al ( 2023 ) investigated the impact of the molar mass of the polymer acceptor in PM6:PYIT all-polymer solar cells. Their findings revealed a substantial influence of the A polymer's length on the aggregation behavior and overall performance of the polymer blend.…”

Revealing the Role of Dynamic and Static Disorder on Charge-Transfer-State Absorption in Polymer Solar Cells

“…Organic heterojunctions, which consist of a mixture of an electron donor and an electron acceptor, are commonly used as functional layers in most high-performance polymer solar cells (PSCs). − For such a system, one of the features is the presence of a large number of donor/acceptor (D/A) interfaces, which not only promotes the dissociation of strongly bound excitons into weakly bound interface charge-transfer (CT) states (or free charges) − but also enriches the photophysical processes. For instance, under the measurement of ultrafast and highly sensitive technologies, additional weak absorption signals, which appear well below the optical gap of the donor and acceptor, have been successively observed in different D/A systems. − Several potential mechanisms, such as doping, defect, and polaron-related absorption, have been proposed to explain the origin of these signals. − In recent years, more works have demonstrated that the weak absorption signal also comes from direct CT absorption at D/A interfaces. , In other words, a bound CT state can be generated at the D/A interface without undergoing a conventional process, where electrons in the exciton transfer from the donor to the acceptor.…”