基于Re-BCP为缓冲层有机太阳能电池性能的研究

有机太阳能电池(OSCs)因成本低、质量轻、柔性 和可大面积制备等优点而被广泛关注。本文通过定向合成有机配合物Re-BCP,首次将其作 为阴极缓冲层引入到OSCs中。通过实验发现,OSCs效率与Re-BCP层厚度密切相关。在标准 太阳光照条件下,结构为ITO/CuPc(20nm)/C60(40nm)/Re-BCP(x nm)/Al(100nm)器件的效率随着Re-BCP厚度的增加先增大后变 小,当其厚为0nm时,效率为0.65%;厚为7nm时,效率为1.10%;而当厚为10nm时,效率降为0.50%。结合器件结构,探讨了器件性能提高的机理。     

Bathocuproine作为缓冲层改善Rubrene/C70太阳能电池的性能

制备了结构为ITO/Rubrene/C70/BCP/Al的双层有机太阳能电池(OSCs),通过优化缓冲层BCP的厚度研究了BCP对OSCs性能的影响及其作用机理。实验发现,BCP厚为6nm时,器件的效率最高达到1.78%,同时获得了较大的开路电压0.901V。相对于没有缓冲层,器件的效率、短路电流、开路电压和填充因子分别提高了432.9%、74.8%、95.4%和55.5%。     

MoO3对有机太阳能电池性能影响的研究

采用MoO3作为阳极缓冲层,制备了结构为ITO/MoO3/P3HT/C60/Bphen/Ag的有机太阳能电池器件,研究了MoO3薄膜厚度对器件性能的影响。采用常用的等效电路模型,仿真计算得到MoO3缓冲层对器件串联电阻的影响。此外,测试了器件的吸收光谱,研究了MoO3缓冲层对器件光子吸收的作用。结果表明,在MoO3厚度为1 nm时,器件的短路电流密度、开路电压和填充因子都得到了提高。MoO3可以改善电极和有机层的界面接触性能,能够有效降低器件的串联电阻,提高载流子的传输和收集效率;同时,MoO3缓冲层透过率高,不会对器件的光吸收效率造成影响。     

基于CuBB为阴极缓冲层有机太阳能电池性能的研究

通过定向合成Cu(I)配合物,首次将 其作为阴极缓冲层引入到有机太阳能电池(OSCs)中。实验分析发现,OSCs的光电能量转换效 率(PCE)与CuBB层厚度紧密相关,在标准太阳 光照条件下,结构为ITO/CuPc (20nm)/C60(40nm)/CuBB (x m m)/Al (100nm)的器件PCE随着CuBB厚度的增加 先增大后变小,当厚为8nm 时PCE达到0.94%。器件性能提高的原因主要是CuBB具有良好 的电子迁移率,但厚度过大时则由于串联电阻增加及电子不能经阴极缓冲层传输而使性能降 低。     

热处理对Rubrene/C70有机太阳能电池性能的改善

制备了ITO/MoO3(6nm)/Rubrene(30nm)/C70(30nm)/BCP(6nm)/Al(150nm)的PN结构和ITO/MoO3(5nm)/Rubrene(25nm)/Rubrene:C70(5nm)/C70(25nm)/BCP(6nm)/Al(150nm)的PIN结构有机太阳能电池(OSCs)。通过对两种器件进行热处理,研究热处理对OSCs性能的影响。实验表明,在热处理后,PN结构和PIN结构器件的短路电流密度分别达到了3.526mA·cm-2和5.413mA·cm-2,功率转换效率分别达到了1.43%和2.09%。与未经过热处理的器件相比,PN结构和PIN结构器件的短路电流密度、填充因子、功率转换效率分别提高了19.0%、7.1%、28.3%和4.8%、20%、24.1%。可见,热处理可以提高Rubrene/C70OSCs的性能。     

MgF2缓冲层对蓝光OLED性能的影响

为了提高蓝光有机电致发光器件(OLED)的发光性能,将MgF2缓冲层插入ITO阳极与空穴传输层NPB之间,通过优化MgF2的厚度,制备了结构为ITO/MgF2(x nm)/NPB(50nm)/DPVBi:DSA-ph(30nm)/Alq3(30nm)/LiF(0.6nm)/Al(100nm)的高性能蓝光器件。实验结果表明,MgF2厚为1.0nm时,器件性能最佳,对应的器件最大电流效率达到5.51cd/A,最大亮度为23 290cd/m2(10.5V),与没有MgF2缓冲层的标准器件相比,分别提高47.3%和25.2%。对ITO表面的功函数测量结果表明,MgF2缓冲层可以有效修饰ITO表面,降低ITO与NPB之间的势垒高度差,改善空穴的注入效率,从而导致电子和空穴的注入更加平衡,激发机制更高效,实现了高性能的蓝光发射,为实现高效而稳定的全彩显示和白光照明奠定了基础。     

Bphen/Ag/Bphen复合缓冲层对有机太阳电池性能的影响

采用Bphen/Ag/Bphen作为阴极缓冲层,制备了基于CuPc/C60的有机太阳电池,研究了在有机薄膜中加入金属超薄层对器件性能的影响。结果表明,在Bphen缓冲层中加入1 nm的Ag时,器件的电子注入和传输都得到了提高。采用常用的等效电路模型,计算了缓冲层对器件性能参数的影响。发现Bphen/Ag/Bphen可以改善有机层和电极的界面接触性能,降低器件的串联电阻。此外,测试了器件的吸收光谱,研究了复合缓冲层对器件光子吸收的作用,发现加入Ag薄层后提高了器件的光吸收能力。     

阴极缓冲层对m-MTDATA/BAlq有机紫外光探测器性能的影响

制备了有机紫外光探测器(OUV-PD),器件结构为I TO/m-MTDATA(30nm)/m-MTDATA:BAlq(40～60nm,1∶1)/BAlq(40nm)/LiF(1nm)/Al(100nm),并研究了施加Liq、TPBi、Bphen和Zn(4-MeBTZ)₂为阴极缓冲层时对器件性 能的影响。实验结果表明,OUV-PD光响应与阴极缓冲层厚度和电子传输性能紧密相关,在 1.05mW/cm²的波长为365nm UV光照射下,响应度最大值分别达到218mA/W、247mA/W、305mA/W 和283mA/W。     

正置倒置异质结有机小分子太阳能电池

以MoO3为阳极修饰层,以Rubrene/C60为活性层,制备了正置和倒置异质结有机小分子太阳能电池。实验结果表明倒置器件的开路电压Voc、短路电流密度Jsc、填充因子FF和功率转换效率η比正置结构的器件分别提高了34%、20%、25%和102%。当插入BCP阴极缓冲层后,阻挡了热的Al原子对C60层的破坏,对倒置器件的性能没有明显的影响,但却显著改善了正置器件的性能,并分析了MoO3和BCP对倒置和正置器件的作用。     

用ZnS薄膜作为空穴缓冲层的高效率有机发光二极管

用磁控溅射方法制备的ZnS薄膜作为有机发光器件(OLEDs)的空穴缓冲层,使典型结构的 OLEDs(ITO/TPD/Alq/LiF/Al) 的发光性能得到改善.ZnS 缓冲层厚度对器件性能影响的实验结果表明,当ZnS缓冲层厚度为 5 nm 时,器件的亮度增加了2倍多;当ZnS缓冲层厚度为5、10 nm时,器件的发光电流效率增加40%.研究结果表明 ZnS 薄膜是一种好的缓冲层材料,它能够提高器件的发光效率,改善器件的稳定性.     

Novel cathode buffer layer of Ag-doped bathocuproine for small molecule organic solar cell with inverted structure

2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline (C₂₆H₂₀N₂), known as bathocuproine (BCP), is a commonly used cathode buffer layer in conventional structure organic solar cells (OSCs). We demonstrated that BCP layer can also be used as a buffer layer in inverted structure OSCs. Unfortunately, the device exhibited an anomalous kink in the current density–voltage (J–V) characteristics, namely, an S-shaped J–V curve, leading to a low fill factor and low power conversion efficiency (PCE). To improve device performance, Ag-doped BCP layer (Ag:BCP) was used to replace the BCP layer. The results showed that the Ag:BCP layer can eliminate the S-kink in the J–V curve, resulting in a large improvement of fill factor and PCE. The origin of the S-shaped J–V curve was demonstrated to originate from the charge accumulation at the fullerene (C₆₀)/BCP interface. On the contrary, the C₆₀/Ag:BCP interface has favorable electronic properties with beneficial gap states for the transport of free carriers. Together with the good conductivity of Ag:BCP layer and the smooth morphology properties, the device performance was greatly improved by Ag:BCP buffer layer.     

Influence of molar mass ratio,annealing temperature and cathode buffer layer on power conversion efficiency of P3HT:PC71BM based organic bulk heterojunction solar cell

In bulk heterojunction (BHJ) solar cells, the molar mass ratio of donor-acceptor polymers, the annealing temperature (T_an) and the cathode buffer layer plays very consequential role in improving the power conversion efficiency (PCE) by tuning the film morphology and enhancing the charge carrier dynamics. A comprehensive understanding of each of these factors is essential in order to optimize the performance of organic solar cells (OSCs). Albeit there are several fundamental reports regarding these factors, an altogether meticulous correlation of these physical processes with experimental evidence of the photo active layer are required. In this work, we systematically analyzed the influence of different molar mass ratio, the annealing temperature (T_an) and the cathode buffer layer of rrP3HT:PC₇₁BM based BHJ solar cells and their corresponding photovoltaic performances were correlated carefully with their thin film growth structure and energy level diagram. The device having 1:0.8 molar mass ratio of rrP3HT:PC₇₁BM and T_an = 150 °C annealing temperature with Bathocuproine (BCP) as the cathode buffer layer having ITO/PEDOT:PSS/rrP3HT:PC₇₁BM (molar mass ratio = 1:0.8; (T_an = 150 °C)/BCP/Al) configuration showed the best device performance with PCE, ɳ = 4.79%, Jsc = 14.21 mA/cm², V_oc = 0.58 V and FF = 57.8%. This drastic variation in PCE of the device having BCP/Al as the cathode contact compared to the other device configurations is due to the coalesced effects of better hole-blocking capacity of BCP along with Al and better phase separation of the active blend layer at 150 °C annealing temperature. These results explicate the cumulate role of all these physical parameters and their combined contribution to the PCE amendment and overall device performance with rrP3HT:PC₇₁BM based organic BHJ solar cell.     

Simple synthesis of solution-processable oxygen-enriched graphene as anode buffer layer for efficient organic solar cells

Interface material is a must for highly efficient and stable organic solar cells (OSCs) and has become a significant part of OSC research today. Here, low-cost and oxygen functionalized graphene (FG) was synthesized via a simple two-step method for applications in OSCs as anode buffer layer. The FG shows excellent dispersion in aqueous solution and great process compatibility with spin coating process. The introduction of work-function-tunable FG can effectively improve short current density of the devices. The power conversion efficiency of FG-based devices (4.13%, 4.49%, and 7.11% for P3HT:PC₆₁BM, P3HT:PC₇₁BM and PBDTTT-C:PC₇₁BM, respectively) outperforms PEDOT:PSS-based devices (3.67%, 4.17%, and 6.46%, respectively). Moreover, the stability of the devices was improved with FG as anode buffer layer compared to PEDOT:PSS. The results indicate that simple synthesized FG is a promising solution-processed anode buffer layer material for high-efficiency and stable OSCs.     

A low-cost and low-temperature processable zinc oxide-polyethylenimine (ZnO:PEI) nano-composite as cathode buffer layer for organic and perovskite solar cells

Nanocomposite buffer layer based on metal oxide and polymer is merging as a novel buffer layer for organic solar cells, which combines the high charge carrier mobility of metal oxide and good film formation properties of polymer. In this work, a nanocomposite of zinc oxide and a commercialized available polyethylenimine (PEI) was developed and used as the cathode buffer layer (CBL) for the inverted organic solar cells and p-i-n heterojunction perovskite solar cells. The cooperation of PEI in nano ZnO offers a good film forming ability of the composite material, which is an advantage in device fabrication. In addition, power conversion efficiency (PCE) of the ZnO:PEI CBL based device was also improved when compared to that of ZnO-only and PEI-only devices. The highest PCE of P3HT:PC₆₁BM and PTB7-Th:PC₆₁BM devices reached to 3.57% and 8.16%, respectively. More importantly, there is no obvious device performance loss with the increase of the layer thickness of ZnO:PEI CBL to 60 nm in organic solar cells, which is in contrast to the PEI based devices, whose device performance decreases dramatically when the PEI layer thickness is higher than 6 nm. Such a nano composite material is also applicable in inverted heterojunction perovskite solar cells. A PCE of 11.76% was achieved for the perovskite solar cell with a thick ZnO:PEI CBL (150 nm) CBL, which is around 1.71% higher than that of the reference cell without CBL, or with ZnO CBL. In addition, stability of the organic and perovskite solar cells having ZnO:PEI CBL was also found to be improved in comparison with that of PEI based device.     

Stable CdTe thin film solar cells with a MoOx back‐contact buffer layer

MoO_x thin films were employed as a buffer layer in the back contact of CdTe solar cells. A monograined CdS layer was employed as the window layer to reduce light absorption. The insertion of a MoO_x buffer layer in the back contact greatly reduced the Schottky barrier leading to increased fill factor and open‐circuit voltage. A CdTe solar cell, with an efficiency as high as 14.2%, was fabricated. The use of a MoO_x buffer layer made it possible to fabricate high‐efficient CdTe solar cell with much less Cu in the back contact, thus greatly enhancing the cell stability. Copyright © 2015 John Wiley & Sons, Ltd.     

MoO3修饰氧化石墨烯作为空穴注入层影响研究

研究了MoO₃修饰氧化石墨烯(GO)作为空穴注入层的影响。采用旋涂的方法制备了GO, 再真空蒸镀修饰层MoO₃,得到了空穴注入能力强和透过率高的复合薄膜。MoO₃的厚分 别采用0、3、5和8nm。通过优化MoO₃的厚度发现,当MoO₃的厚为5nm时,复合薄膜 的透过率达到最大值,在 550nm的光波长下透光率为88%,且此时采用 复合薄膜作为空穴注入层制备的结构为 ITO/GO/MoO₃(5nm)/NPB(40nm)/Alq₃(40nm)/LiF(1nm)/Al(100nm)的有机电致发光器件(OLED)性能 最佳。通过对OLED进一步的优化,改变Alq₃的厚度,分别取50、60和70nm,测量其电压 、电流、亮度、色坐标和电致发光(EL)光谱等参数发现,当Alq₃的厚为50nm时器件性能最 佳。最终制备了结构为ITO/GO/MoO₃(5nm)/NPB(50nm)/Alq₃(50nm)/LiF(1nm)/Al(100 nm)的OLED,在电压为10V时,最大电流效率达到5.87cd/A,与GO单独作为空穴注入层制备的器件相比,提高了50%。     

An antimonene modified hole extraction layer for high efficiency PEDOT:PSS-free nonfullerene organic solar cells

In this paper, a bilayer hole extraction layer (HEL) with solution-processed molybdenum trioxide (MoO₃) and two-dimensional (2D) material of antimonene was developed to achieve high performance nonfullerene organic solar cells (NF–OSCs). The application of antimonene facilitates effective charge extraction and lowered recombination loss, achieving improved photovoltaic performance. By inserting the antimonene layer, power conversion efficiency (PCE) of devices with MoO₃ HEL was increased from 8.92% to 11.30% in OSCs with non-fullerene systems of PBDB-T-2F:IT-4F, which was even much higher than that of the devices with PEDOT:PSS HEL (10.59%). Results make it clear that the solution-processed bilayer MoO₃/antimonene HEL shows great potential for application in high performance PEDOT:PSS-free NF–OSCs.     

Silicon germanium active layer with graded band gap and µc-Si:H buffer layer for high efficiency thin film solar cells

We investigated solar cells with graded band gap hydrogenated amorphous silicon germanium active layer and hydrogenated microcrystalline silicon buffer layer at the interface of intrinsic and n-type doped layer. A significantly improved, 10.4% device efficiency was observed in this type of single junction solar cell. The intrinsic type microcrystalline silicon buffer layer is thought to play dual roles in the device; as a crystalline seed-layer for growth of n-type hydrogenated microcrystalline silicon layer and helping efficient electron collection across the i/n interface. Based on these, an enhancement in cell parameters such as the open-circuit voltage (V_oc), and fill factor (FF) was observed, where the FF and V_oc reaches up to 69% and 0.85 V respectively. Our investigation shows a simple way to improve device performance with narrow-gap silicon germanium active layer in solar cells in comparison to the conventionally constant band gap device structure.     

Flexible organic solar cells using an oxide/metal/oxide trilayer as transparent electrode

Organic solar cells (OSCs) have attracted much attention as a clean and renewable energy convention system, owning to the low-cost and easy-processing nature of organic semiconductors. While indium tin oxide (ITO) is commonly used in OSCs as the transparent conductive electrode, the rising cost of indium, the high temperature process and the poor flexibility of ITO, make it incompatible with large-scale roll-to-roll manufacture of OSCs. In this paper, the MoO₃/thin metal/MoO₃ trilayer structure was used to replace the ITO electrode in OSCs. The optical and electrical properties of the trilayer were shown to depend on the material and thickness of the intermediate metal layer. The maximum power conversion efficiency of up to 2.5% under simulated 1 sun AM 1.5 solar illumination was achieved for OSCs based on poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM), compared to a maximum efficiency of 3.1% for the ITO-based devices. Moreover, due to the flexible nature of the trilayer structure, the OSCs with the trilayer electrode exhibited good mechanical flexibility. The efficiency of the flexible device was only reduced by ∼6% from its original performance after 500 bending cycles with a bending radius of 1.3 cm. Therefore, the performance of the ITO-free devices on rigid/flexible substrates suggests that this oxide/metal/oxide trilayer electrode is a promising ITO replacement in OSCs.