Grain structure control and greatly enhanced carrier transport by CH3NH3PbCl3 interlayer in two-step solution processed planar perovskite solar cells

We report that the use of a CH3NH3PbCl3 interlayer onto the PEDOT:PSS layer in the two-step solution deposition of CH3NH3PbCl3 for planar p-i-n type perovskite solar cells (PSCs) can lead to a dramatic enhancement of short-circuit current density (J(SC)) by 52.8% from 13.07 mA cm(-2) to 19.98 mA cm(-2). While the absorption and thus the composition of the perovskite layers remain unchanged, Incident photon-to-current efficiency (IPCE) measurement results reveal much enhanced carrier transport, which in turn can be correlated to the larger and more columnar grain structure in the perovskite layer with the use of the CH3NH3PbCl3 interlayer. On the other hand, the two-step solution processed perovskite layers without the CH3NH3PbCl3 interlayer exhibit smaller and more cross-hatching grain structure and yield significantly smaller J(SC). Therefore our results revealed clearly that the insertion of CH3NH3PbCl3 interlayer, which affects the nucleation dynamics, may control the grain structure of the two-step solution processed perovskite layers and improve dramatically the photovoltaic performance of the resultant planar p-i-n type PSCs. Our CH3NH3PbCl3 interlayer may thus serve as an effective method for p-i-n PSCs to achieve high J(SC) with thicker perovskite layer. (C) 2016 Elsevier B.V. All rights reserved.