Organic solar cells (OSCs) with thick active layers exhibit great potential for future roll‐to‐roll mass production. However, increasing the thickness of the active layer generally leads to unfavorable morphology, which decreases the device's performance. Therefore, it is a critical challenge to achieve OSCs with high efficiency and thick film simultaneously. Herein, a small molecular donor, ZW1, incorporating a bithiazole unit along with a thiophene group as a π‐bridge is reported. ZW1 with high crystallinity is employed to fabricate D18:ZW1:Y6 ternary devices, which enhances the crystallization, optimizes the morphology, and suppresses bimolecular recombination. Additionally, ZW1 shows better miscibility with D18, resulting in the preferred vertical phase distribution. As a result, an outstanding power conversion efficiency (PCE) of 18.50% is realized in ternary OSCs with 120 nm active layer thickness. Importantly, the thick ternary OSCs attain a high PCE of 16.67% (thickness ≈300 nm), significantly higher than the corresponding binary devices (13.50%). The PCE of 16.67% is one of the highest values for thick‐film OSCs reported to date. This work demonstrates that the incorporation of highly crystalline small‐molecule donors into ternary OSCs, possessing good miscibility with host materials, presents an effective strategy for fabricating highly efficient thick OSCs.

No abstract

Comprehensive Summary All‐small‐molecule organic solar cells (ASM OSCs) are promising for commercial application due to the well‐defined chemical structures, convenient purifying process and low batch‐to‐batch variation. However, the similarity of molecule structures between small molecule donors and acceptors makes a hard regulation of their blend morphology, which will limit the efficiency. One of the efficient approaches is structural tuning, among which the π‐bridge engineering is considered as a good method to improve the blend morphology. Herein, we synthesized two porphyrin‐based small‐molecule donors, Por‐BR and Por‐TR, by introducing alkoxybenzene and alkylthiophene as π bridges. The Por‐BR‐based active layer produces poor morphology and does not achieve satisfying device efficiency because of the excessive aggregation tendency. As for Por‐TR, an efficiency of 11.26% is achieved with such a high open circuit voltage of 0.904 V. This study shows that altering π‐bridge units can facilitate the improvement of film morphology, finally increase the device performance, and also provides a sample for molecule designing in terms of structure‐property correlation.

With the tactful material design, skillful device engineering, and in‐depth understanding of morphology optimization, organic solar cells (OSCs) have achieved considerable success. Therefore, OSCs have reached high power conversion efficiencies (PCEs) exceeding 19%. Especially, continuously emerging new materials have been considered as one of the key factors to improve the PCEs of OSCs. Among molecular design strategies, side‐chain engineering is an easy and commonly‐used means which can optimize the solubility, alter intermolecular stacking arrangement, fine‐tune the open circuit voltage (VOC), thus ultimately improve the performance. As hybrid side chains, silane and siloxane side chains have considerable effects, not only in increasing the carrier mobility and tuning the energy level, but also in affecting the crystallinity and molecular orientation.In this review, the latest developments in photovoltaic materials based on silane and siloxane side chains are presented to illustrate the structure‐property relationships. The review comprehensively includes silane‐side based polymer/small molecule donors; siloxane‐side based polymer/small molecule donors, and polymer/small molecule acceptors. Then the similarities and differences between these two side chains are demonstrated. Finally, the possible applications and future prospects of silane and siloxane side chains are presented.This article is protected by copyright. All rights reserved.