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TOPIC：Controlling Microstructure, Morphology and Defects in Perovskite Solar Cells
SPEAKER：Prof. Martyn A. McLachlan，Imperial College London
TIME： 2019年8月6日，下午4:00 
LOCATION：化学B楼410室
INVITER：钟洪亮 特别研究员


 
Abstract
Perovskite solar cells (PSCs) continue to stimulate intense research activity with a multitude of processing modifications, obscure additives and some good old-fashioned chemistry being cited as the underlying reasons for improvements in PSC performance. Of the growing volume of PSC literature that exists a small quantity focuses on minor changes to the processing methodology employed and/or additives that have been cited to be responsible for a variety of measurable improvements in device performance. Here I will discuss several recent case studies where processing modifications have been investigated as a means of controllably varying active layer crystallinity. 

First we use scanning transmission electron microscopy (STEM) to locate previously unobserved nanoscale defects residing within individual grains of solution‐processed methylammonium lead tri‐iodide (CH3NH3PbI3, MAPI) thin films, these defects are associated with the established solution processing methodology-hence we introduce a facile processing modification to eliminate them and improve performance. 

We investigate the role of solvent annealing combined with the addition of bulky cation additives- we do not identify 2D perovskite or Ruddlesden-Popper phase material, rather a surface decoration of the additives that suppresses non-radiative recombination resulting from charge trapping and the formation of massive, monolithic perovskite grains formed during solvent annealing.

In both case studies we identify microstructural modifications in the active layer and correlate these with the observed performance improvements, using a variety of spectroscopic probes to support our observations.