Mapping Morphological and Structural Properties of Lead Halide Perovskites by Scanning Nanofocus XRD

Abstract

Scanning nanofocus X-ray diffraction (nXRD) performed at a synchrotron is used to simultaneously probe the morphology and the structural properties of spin-coated CH$_3$NH$_3$PbI$_3$ (MAPI) perovskite films for photovoltaic devices. MAPI films are spin-coated on a Si/SiO$_2$/poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) substrate held at different temperatures during the deposition in order to tune the perovskite film coverage. The films are then investigated using nXRD and scanning electron microscopy (SEM). The advantages of nXRD over SEM and other techniques are discussed. A method to visualize, selectively isolate, and structurally characterize single perovskite grains buried within a complex, polycrystalline film is developed. The results of nXRD measurements are correlated with solar cell device measurements, and it is shown that spin-coating the perovskite precursor solution at elevated temperatures leads to improved surface coverage and enhanced solar cell performance.This work was funded by the UK Engineering and Physical Sciences Research Council via grants EP/M025020/1 “High resolution mapping of performance and degradation mechanisms in printable photovoltaic devices,” EP/J017361/1 (Supersolar Solar Energy Hub) and the E-Futures Doctoral Training Center in Interdisciplinary Energy Research EP/G037477/1. This work was partially funded by the President of the UAE’s Distinguished Student Scholarship Program (DSS), granted by the Ministry of Presidential Affairs, UAE (M.A. PhD scholarship). This work was also partially funded by the Masdar Institute through the grant Novel Organic Optoelectronic Devices. The authors gratefully acknowledge Manfred Burghammer and Martin Rosenthal at the ID13 – the microfocus beamline at the ESRF for their assistance with the nXRD measurements. XMaS is a mid-range facility supported by the Engineering and Physical Sciences Research Council (EPSRC)