The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
ACS Appl Mater Interfaces. 2012 May;4(5):2534-40. doi: 10.1021/am300228w. Epub 2012 Apr 20.
We report the use of two solution-processable triindoles, triazatruxene (TAT), and N-trimethyltriindole (TMTI), as hole selective materials in organic solar cells. The unique optical and electronic properties of these molecules make them suitable as a hole extracting/electron blocking layer, i.e. transparency in the visible region due to a wide bandgap, high LUMO (lowest unoccupied molecular orbital) energy level, modest HOMO (highest occupied molecular orbital) level, and high hole carrier mobility. TAT is shown to have a LUMO at -1.68 eV, a HOMO at -5.03 eV, and a bandgap of 3.35 eV, whereas TMTI has a LUMO at -2.05 eV, a HOMO at -5.1 eV, and a bandgap of 3.05 eV, obtained from cyclic voltammetry measurements and absorption spectroscopy. Planar heterojunction photovoltaic devices, consisting of a solution processed transparent TAT (or TMTI) layer and a vapor-deposited C60 layer, exhibited efficiencies of up to 0.71 % (or 0.87 %). In these bilayer devices, the excitons are primarily generated in the C60 layer and undergo dissociation in the interfaces via hole transfer from the C60 layer to the TAT (or TMTI) layer. Additionally, spin-casting methanol solution of TAT on the top of P3HT:PCBM bulk heterojunction in an inverted device produced a hole selective interfacial layer between the photoactive layer and anode, leading to a 26% efficiency increase as compared to a control device without the TAT layer.
我们报告了两种可溶液处理的三吲哚，即三嗪并三苯（TAT）和 N-三甲基三吲哚（TMTI），作为有机太阳能电池中的空穴选择材料的应用。这些分子独特的光学和电子性质使它们适合作为空穴提取/电子阻挡层，即在可见光区域具有高透明度，因为具有宽能带隙、高 LUMO（最低未占据分子轨道）能级、适度的 HOMO（最高占据分子轨道）能级和高空穴载流子迁移率。TAT 的 LUMO 能级为-1.68 eV，HOMO 能级为-5.03 eV，带隙为 3.35 eV，而 TMTI 的 LUMO 能级为-2.05 eV，HOMO 能级为-5.1 eV，带隙为 3.05 eV，这些数值是通过循环伏安法测量和吸收光谱法获得的。由溶液处理的透明 TAT（或 TMTI）层和气相沉积的 C60 层组成的平面异质结光伏器件，其效率高达 0.71%（或 0.87%）。在这些双层器件中，激子主要在 C60 层中产生，并通过从 C60 层到 TAT（或 TMTI）层的空穴转移在界面处发生离解。此外，在倒置器件中，将 TAT 的甲醇溶液旋涂在 P3HT:PCBM 体异质结的顶部，可以在光电活性层和阳极之间形成空穴选择性界面层，与没有 TAT 层的对照器件相比，效率提高了 26%。
