In this study, novel nanocomposites consisting of zinc oxide (ZnO) and a polymer polyethylenimine ethoxylated (PEIE) are fabricated by blending sol–gel ZnO dispersions with different concentrations of PEIE in solution. The photoelectric properties of ZnO:PEIE composites are characterized by a series of testing methods. The results show that PEIE as a doping agent can effectively modify and passivate the surface of ZnO nanoparticles, and ZnO:PEIE composite at 0.1 wt% PEIE possesses the highest conductivity and the lowest work function. Moreover, the ZnO and ZnO:PEIE composites with different concentrations of PEIE are used as electron transport layers (ETLs) in polymer solar cells (PSCs). Compared to pure ZnO as ETL, the power conversion efficiency (PCE) of the device based on P3HT:PCBM with ZnO:PEIE (0.1 wt% PEIE) as ETL is effectively improved from 3.01% to 3.52%. For the device based on PTB7:PCBM with ZnO:PEIE (0.1 wt% PEIE) as ETL, the PCE is improved from 6.92% to 8.03%. It is found that PEIE can not only reduce the surface defects and traps of ZnO nanoparticles, but also prevent the aggregation of ZnO precursor. Moreover, the addition of PEIE does not change the shape of synthetic nanometer ZnO materials, and the Fermi level of ZnO thin films is also gradually decreased with the addition of PEIE, which helps to reduce the electronic transmission barrier. Accordingly, ZnO:PEIE composites can be effective ETLs in PSCs.
Jingyu Peng,Ting Wang,Rujing Wang,Song Wang,Hanzhuang Zhang,Xulan Xue,Wenyu Ji
Interfaces between functional layers are among the most crucial and intricate structures in electronic devices with a multilayer structure; they determine the injection and distribution of charge carriers, as well as the efficiency and stability of the devices. Here, a general but previously overlooked acidic surface of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films is investigated in detail to construct efficient perovskite light-emitting diodes. This potent acidity leads to the decomposition of perovskites by the diffusion of active protons coming from the PSSH components in PEDOT:PSS. A polyethylenimine ethoxylated (PEIE) modifying layer is used to neutralize the PSSH on the surface of PEDOT:PSS films, which not only protects the perovskites, but also enhances device efficiency greatly. A peak current efficiency of 56.7 cd/A is obtained, enhancing by about 7 times compared with the control device without PEIE (7.8 cd/A). Our work addresses a long-standing but seldom-discussed issue in perovskite light-emitting diodes—the strong dependence of device performance on the surface characteristics of PEDOT:PSS films.
Hao Xiong,Bowen Li,Hongjie Qiu,Pengfei Liu,Kunyuan Zheng,Zening Lei,Peng Xiang,Xinyu Tan
Perovskite solar cells (PSCs) have attracted considerable research interest in recent decades due to their remarkable power conversion efficiencies. However, their thermal stability is remains one of the crucial challenges for commercial applications. Bathocuproine (BCP), widely employed as an interfacial buffer layer between the electron transport layer and the metal electrode, tends to undergo thermal aggregation at elevated temperatures, thereby compromising device stability. In this paper, the aggregation behavior of BCP under thermal stability test was investigated. It was proposed that introducing Polyethylenimine (PEIE) into BCP could inhibit its high-temperature aggregation. The -NH and -OH groups in PEIE can form hydrogen bonds with pyridine nitrogen in BCP. This interaction enables moderate π-π stacking between to exist within a wider temperature and improves the morphology and uniformity of the film. Concurrently, PEIE improves energy level alignment at the C60/BCP interface, facilitating more efficient electron extraction and transport. Moreover, the incorporation of PEIE remarkably suppresses the infiltration of Ag ions under continuous thermal conditions, which further boosts the thermal stability of the device. By utilizing the PEIE-modified BCP buffer layer, the resulting PSCs demonstrate a champion power conversion efficiency (PCE) of 25.83%. Even after 1000 hours operation under a relative humidity of 30%, it still maintains an efficiency of more than 85% demonstrating significantly enhanced stability. This work presents an innovative design strategy for developing PSCs with simultaneously enhanced efficiency and operational stability.
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