Fig. 4: Grain-size effect of MAPbI3 perovskite films.
From: 2D materials for conducting holes from grain boundaries in perovskite solar cells
a–d Plan view and corresponding cross-sectional view of the scanning electron microscopy (SEM) images of perovskite films with different grain sizes on FTO/TiO2 substrates. The length of all the scale bars is 500 nm. The average grain sizes of the perovskite films in a–d are 200, 250, 300 and 390 nm, respectively. e, f J–V curves of the PSCs without (control) and with BP (2 coats) deposited on perovskite films. g Average PCEs and relative PCE enhancement (after the BP modification) of PSCs with different perovskite grain sizes. The black curve (control) and red curve (BP) correspond to the PCEs of devices without and with the BP modification, respectively, while the green columns represent the relative PCE enhancement after the BP modification
