How Deep Hole Traps Affect the Charge Dynamics and Collection in Bare and Bilayers of Methylammonium Lead Bromide.

Wide-band-gap perovskites such as methylammonium lead bromide (MAPB) are promising materials for tandem solar cells because of their potentially high open-circuit voltage, which is yet still far below the maximum limit. The relatively short charge-carrier lifetimes deduced from time-resolved photoluminescence (TRPL) measurements seem in strong contrast with the long lifetimes observed with time-resolved photoconductance measurements. This is explained by a large amount of hole defect states, > 10 cm, in spin-coated layers of MAPB residing at or near the grain boundaries.

Calibrating lateral displacement sensitivity of AFM by stick-slip on stiff, amorphous surfaces.

We calibrate the lateral mode AFM (LFM) by determining the position-sensitive photodetector (PSPD) signal dependency on the lateral tip displacement, which is analogous to the constant-compliance region in normal-force calibration. By stick-slip on stiff, amorphous surfaces (silica or glass), the lateral tip displacement is determined accurately using the feedback loop control of AFM system. The sufficiently high contact stiffness between the Si AFM tip and stiff, amorphous surfaces substantially reduces the error of PSPD signal dependency on the lateral tip displacement.

Fast and controlled fabrication of porous graphene oxide: application of AFM tapping for mechano-chemistry.

This paper describes a novel method to fabricate porous graphene oxide (PGO) from GO by exposure to oxygen plasma. Compared to other methods to fabricate PGO described so far, e.g.