Enhanced photovoltaic performance of perovskite solar cells based on sufficient pore-filling in the mesoporous TiO_2 electron transport layer

摘要

Mesoporous TiO_2 (m-TiO_2) layer has been widely used as a photoelectrode of solar cells. Compared with conventional planar TiO_2 layer, appropriate pore size dramatically improves infiltration of perovskite (PVK) into the mesoporous layer because of the larger voids formed within the TiO_2 mesoporous layer and further enhances the light absorption efficiency of PVK for the better light-scattering ability of 20 nm TiO_2 nanoparticles. In our study, 75-95 nm pore size of TiO_2 scaffold layer was successfully prepared by adding different contents of ethyl cellulose (EC) as a template and terpineol as a leveling agent into conventional TiO_2 paste composed of 20 nm-sized TiO_2 nanoparticles and then applied to PVK solar cells (PSCs).The novel mesoporous layer was conducive to increase light-harvesting capacity and photovoltaic performance of PSCs. The influence of different contents of EC was discussed systematically for TiO_2 scaffold layer, the charge carrier dynamic, and the hysteresis behavior for our devices. Finally, by optimizing the parameters of the electron transport layer, the power conversion efficiency of the champion device with a 16.5% mass fraction of EC reached as high as 18%.