Efficient and stable mesoporous perovskite solar cells using p-type poly (9-vinylcarbazole) modified the interface of perovskite/mesoporous TiO2 layers

Abstract A p-type poly(9-vinylcarbazole) (PVC) was inserted into the interface between perovskite and mesoporous TiO2 electron transport layers. The ultrathin PVC modified TiO2 layer can obviously improve the crystallinity of perovskite layer with less pinholes, passivate the interface and inhibit hole carriers transport into the interface of perovskite/TiO2 electron transport layers. The perovskite film modified with PVC shows larger grain sizes and more compact films, which helps to increase photocurrent and reduce the leak current of cells. The passivating interface with less hole carrier accumulation and hydrophobicity can greatly reduce carrier recombination, improve carrier transport and extraction abilities and cells stability. Therefore, perovskite solar cells (PSCs) with PVC modified TiO2 layer exhibited a power conversion efficiency (PCE) of 19.02%, which is remarkably higher than that (16.09%) of the reference cells. Furthermore, PSCs without and with PVC modification respectively retained 20% and 55% of the initial PCE values aging for 30 days at the relative humidity 15% in air without encapsulation. For thermal stability test, the pervoskite layers were heated for 10 h at 100 °C before further spin-coating Spiro-OMeTAD, PSCs with PVC modification were still remained 70% of the original PCEs, which is greatly higher than that (30%) of the reference cells. These results indicate that PSCs with PVC modified TiO2 layer can effectively improve PCEs and show better moisture resistance and thermal stability.