Contents lists available at ScienceDirect Solar Energy Materials and Solar Cells journal homepage: www.elsevier.com/locate/solmat Radiative and conductive thermal annealing of hybrid organic-inorganic perovskite layer Bosky Sharma a , Shivam Singh c , Shiwani Pareek b , Amrut Agasti b , Sudhanshu Mallick a,b , Dinesh Kabra a,c,* , Parag Bhargava a,b,** a Centre for Research in Nano-Technology and Science, Indian Institute of Technology Bombay, 400076, India b Department of Metallurgical Engineering and Material Science, Indian Institute of Technology Bombay, 400076, India c Department of Physics, Indian Institute of Technology Bombay, 400076, India ARTICLE INFO Keywords: Near Infrared (NIR) radiations annealing Crystallization MAPbI 3 ABSTRACT We report an alternative method adopting Near InfraRed (NIR) radiations for annealing CH 3 NH 3 PbI 3 (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. 1. Introduction Organic-inorganic hybrid perovskite material as an absorber layer has revolutionized solar photovoltaics domain because of the unique combination of versatile optical and electrical properties than existing materials [1]. The solution processing methods, ease of deposition on flexible substrate, less expensive precursor salts, easy tuning of the band gap, high absorption coefficient, flexible architecture, high carrier mobility, long exciton diffusion length and low non-radiative carrier recombination rates make perovskite potentially competitive with ex- isting photovoltaics technologies [1]. Methyammonium lead iodide (MAPbI 3 ) is the most commonly used material in the perovskite pho- tovoltaic community due to its high absorption coefficient, high carrier mobility, long exciton diffusion length and small binding energy [2]. In 2009, for the first time Miyasaka et al. reported 3.9% power conversion efficiency (PCE) perovskite-based solar cells [3]. Within a short span of time, hybrid organic–inorganic perovskites described by the formula ABX 3 (A = CH 3 NH 3 + ; B = Pb 2+ or Sn 2+ ; and X = Cl - ,I - , and/or Br - ) have been intensively studied as an emerging material for solar energy harvesting due to impressive power conversion efficiency over 20% [4–7]. Perovskite solar cells have been fabricated by em- ploying low temperature solution methods such as spin-coating, vapor deposition techniques using one-step [8], two-step [6,9]vapor assisted deposition [10], anti-solvents [11,12] and additive methods [13,14]. It can be stated that performance of perovskite solar cells, besides many other factors, critically depends on precursor composition, annealing methods used for preparing the perovskite layer and the resulting morphology, [15]. The most common annealing process for MAPbI 3 films is thermal annealing at 100 °C for 10 min on hot plate [16,17]. There has been a focus on obtaining highly crystalized, homogeneous, conformal and smooth perovskite films by introducing new annealing methods like hot cast [18] and solvent annealing [19]and altering ex- isting thermal annealing like high temperature [20]and multistep [21] or ramped annealing. In addition, hot plates in general have various heat zones and there is always slightly lower temperature away from centre of the hot plate. We note that such variations can lead to irre- producible results from device to device commonly observed in per- ovskite community. These cumbersome methods possess bottleneck in https://doi.org/10.1016/j.solmat.2019.03.022 Received 21 October 2018; Received in revised form 6 March 2019; Accepted 9 March 2019 * Corresponding author. Centre for Research in Nano-Technology and Science, Indian Institute of Technology Bombay, 400076, India. ** Corresponding author. Centre for Research in Nano-Technology and Science, Indian Institute of Technology Bombay, 400076, India. E-mail addresses: boskiisharma@gmail.com (B. Sharma), dkabra@iitb.ac.in (D. Kabra), pbmatsc@gmail.com (P. Bhargava). Solar Energy Materials and Solar Cells 195 (2019) 353–357 0927-0248/ © 2019 Elsevier B.V. All rights reserved. T