Radiative and conductive thermal annealing of hybrid organic-inorganic perovskite layer

We report an alternative method adopting Near InfraRed (NIR) radiations for annealing CH3NH3PbI3 (MAPbI(3)) films. This technique provides fast crystallization of perovskite domains as thermal energy is transferred through radiation (non-contact) as well as conduction (contact) mode. While, in case of conventional annealing method (hot plate), thermal energy is released through conduction (contact) mode only. The champion cell fabricated via NIR radiation annealing method shows power conversion efficiency (PCE) of 12.33% compared to 10.92% by conventional hot plate thermal annealing. The films are characterized by morphological (SEM), optical (UV-ViS) and structural (XRD) aspects. The improved performance owes to smooth and compact morphology, higher absorption, enhanced crystallinity, lower series resistance, improved charge separation and collection in case of NIR annealed perovskite films. The charge transfer resistance and series resistance of interfaces are manifested by Electrochemical Impedance spectroscopy (EIS). It can be stated that method and mode of annealing plays a great role in crystallization of perovskite films, which can be adopted for large area industrial processing techniques for these materials.