In this study, we synthesized a series of four large-band gap small molecule acceptors with side-chain engineering of the dithieno-pyrrolo-fused pentacyclic benzotriazole (BZTTP or Y1 core) or the fused-ring dithienothiophene-pyrrolobenzothiadiazole (TPBT or Y6 core) with difluoro-indene-dione (IO2F) or dichloro-indene-dione (IO2Cl) end groups to form Y1-IO2F, Y1-IO2Cl, Y6-IO2F, and Y6-IO2Cl acceptors, respectively, for blending with poly(3-hexyl thiophene) (P3HT) for bulk heterojunction organic photovoltaics. The complementary UV–vis absorption spectra of these small molecules and P3HT along with their offset energy bands allow broad absorption and effective electron transfer. Through synchrotron wide-angle X-ray scattering (WAXS) analyses and contact angle measurements, we found that the blend of the small molecule Y6-IO2F (having a TPBT core) and P3HT achieves an optimum morphology that balances their crystallinity and miscibility, among those of these four blends, leading to a substantial enhancement in the short-circuit current density and thus power conversion efficiency (PCE) in their devices. For example, the P3HT:Y6-IO2F (w/w: 1/1.2) device exhibited a champion PCE of 10.5% with a short current density (J_sc) value of 15.9 mA/cm² as compared to the P3HT:Y1-IO2F device having a PCE of 2.2% with a J_sc value of 5.7 mA/cm² because of the higher Y6-IO2F (with TPBT core) molecular packing that facilitated carrier transport in the devices. The enhanced thermal stability exhibited by the devices incorporating Y6-IO2F and Y6-IO2Cl, as compared to that of Y1-IO2F and Y1-IO2Cl devices, is also due to the more planar TPBT core structure, while the photostability of devices incorporating Y6-IO2Cl and Y1-IO2Cl is better than that of devices incorporating Y6-IO2F and Y1-IO2F, owing to more photostable chemical structures. These results present an outstanding performance for P3HT-based organic solar cells. Moreover, these small molecule blends are processed with an environmentally friendly solvent tetrahydrofuran, demonstrating both the sustainability and commercial viability of these types of organic photovoltaics.

中文翻译：

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基于小分子受体核心单元侧链工程的高性能聚（3-己基噻吩）有机光伏

在本研究中，我们合成了一系列四种大带隙小分子受体，其侧链工程为二噻吩并吡咯稠合五环苯并三唑（BZTTP或Y1核心）或稠环二噻吩并噻吩-吡咯并苯并噻二唑（TPBT或Y6核心） ）与二氟茚二酮（IO2F）或二氯茚二酮（IO2Cl）端基分别形成Y1-IO2F、Y1-IO2Cl、Y6-IO2F和Y6-IO2Cl受体，用于与聚（3-己基噻吩）（P3HT）用于本体异质结有机光伏发电。这些小分子和 P3HT 的互补紫外可见吸收光谱及其偏移能带允许广泛的吸收和有效的电子转移。通过同步加速器广角 X 射线散射 (WAXS) 分析和接触角测量，我们发现小分子 Y6-IO2F（具有 TPBT 核）和 P3HT 的共混物实现了平衡其结晶度和混溶性的最佳形态。这四种混合物的性能显着提高，从而显着提高了器件的短路电流密度，从而提高了功率转换效率 (PCE)。例如，与 P3HT: Y1- 相比，P3HT:Y6-IO2F (w/w: 1/1.2) 器件表现出 10.5% 的冠军 PCE 和15.9 mA/cm ^{2的短电流密度 (} J _sc ) 值。 IO2F器件的PCE为2.2%，J _sc值为5.7 mA/cm ²，因为较高的Y6-IO2F（具有TPBT核）分子堆积有利于器件中的载流子传输。与 Y1-IO2F 和 Y1-IO2Cl 器件相比，包含 Y6-IO2F 和 Y6-IO2Cl 的器件表现出增强的热稳定性，这也是由于更平坦的 TPBT 核心结构，而包含 Y6-IO2Cl 的器件的光稳定性更好。由于具有更光稳定的化学结构，IO2Cl和Y1-IO2Cl比包含Y6-IO2F和Y1-IO2F的器件更好。这些结果展示了基于 P3HT 的有机太阳能电池的出色性能。此外，这些小分子混合物是用环保溶剂四氢呋喃加工的，证明了这些类型的有机光伏电池的可持续性和商业可行性。