McAnally Shaun, Brooks Eucalyptus, Lindsay Oliver, Burn Paul L, Gentle Ian R, Shaw Paul E
Centre for Organic Photonics & Electronics, School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD, 4072, Australia.
Small. 2025 Feb;21(8):e2409485. doi: 10.1002/smll.202409485. Epub 2025 Jan 29.
Y6 homojunction solar cells are prepared using the exciton/electron-blocking material poly[9,9-di-n-octylfluorene-alt-N-(4-sec-butylphenyl)diphenylamine] (TFB) as a secondary hole transport layer material in conjunction with PEDOT:PSS. Using this device architecture, a maximum power conversion efficiency (PCE) of 2.57% is achieved, which is the highest reported thus far for a solution-processed small molecule homojunction organic photovoltaic (OPV) device. The devices display an unexpectedly low thickness dependence, with the average PCE only decreasing by ≈17% when the Y6 active layer thickness is increased from 80 to 300 nm. Time-resolved photoluminescence measurements show that the TFB does not contribute to charge generation through photoinduced hole or electron transfer. However, transient absorption spectroscopy on thin films of neat Y6 and a 1:1 blend of Y6:TFB shows that the TFB enhances the formation of the long-lived Y6 intermolecular charge-transfer state in the blend film. It is found that careful selection of the electron transport layer (ETL) is required to avoid unintended charge generation at the interface with Y6 so as to ensure that the device is a true homojunction. The improved efficiency of this architecture is attributed to the electron-blocking and hole-extraction effects of the TFB layer.
采用激子/电子阻挡材料聚9,9-二正辛基芴-alt-N-(4-仲丁基苯基)二苯胺作为辅助空穴传输层材料，并与PEDOT:PSS结合，制备了Y6同质结太阳能电池。使用这种器件结构，实现了2.57%的最大功率转换效率(PCE)，这是迄今为止溶液处理的小分子同质结有机光伏(OPV)器件报道的最高效率。这些器件显示出出乎意料的低厚度依赖性，当Y6活性层厚度从80 nm增加到300 nm时，平均PCE仅下降约17%。时间分辨光致发光测量表明，TFB不会通过光致空穴或电子转移对电荷产生做出贡献。然而，对纯Y6薄膜和Y6:TFB 1:1混合薄膜的瞬态吸收光谱表明，TFB增强了混合薄膜中长寿命Y6分子间电荷转移态的形成。发现需要仔细选择电子传输层(ETL)，以避免在与Y6的界面处产生意外电荷，从而确保器件是真正的同质结。这种结构效率的提高归因于TFB层的电子阻挡和空穴提取效应。
