Speaker
Description
Surface modification of titanium dioxide (TiO$_2$) substrates was performed to enhance efficiency of perovskite solar cells efficiency by inserting small organic molecules between TiO$_2$ electron transporting layer and CH$_3$NH$_3$PbI$_3$ perovskite layer. TiO$_2$ substrates were immersed into a solution of amino propionic acid (APA) or amino benzoic acid (ABA) in order to tune up and improve surface quality which leads to changes in PbI$_2$ and CH$_3$NH$_3$PbI$_3$ perovskite morphology and structure. Fourier transform infrared spectroscopy (FTIR), field-emission scanning electron microscopes (FE-SEM), X-ray diffraction (XRD) and open-circuit voltage-decay (OCVD) were performed to characterize material and device properties. It was found that introduced organic molecules change the PbI$_2$ precursor morphology which attributes to different trend of efficiency enhancement. Small cracks spreading through PbI$_2$ film coated on TiO$_2$/APA were observed. These cracks promote PbI$_2$ transformation to CH$_3$NH$_3$PbI$_3$ perovskite when reacts with CH$_3$NH$_3$I. The device with APA treatment show the improvement in power conversion efficiency from 6.23% for untreated TiO$_2$ condition to 7.78%. In addition, the OCVD analysis revealed that charge carrier lifetime of APA-treated device is significantly longer than that of the untreated device. These imply that this simple surface modification by small organic molecules could improve efficiency of perovskite solar cells.
