Infrared photon-assisted annealing for crystal engineering in perovskite solar cells

In this study, it was found that infrared-assisted annealing (IAA) was a novel and rapid method for growing of high-qualitied MAPbI 3 films. Compared to traditional thermal annealing, this new strategy combined high-intensity infrared photon flux into annealing process, which achieved the high-qualitied MAPbI 3 film with large crystalline grains and less surface defects. The reaction between MAI and PbI 2 was characterized by confocal laser scanning and X-ray diffraction, which showed the addition of the infrared photons accelerated the reaction of the crystal, and the growth process of perovskite films with the increase of photon number is revealed. The simulation results revealed that infrared photons reduced the critical-free energy of crystallization of MAI and PbI 2 , leading to the rapid growth of grains. Fabricated perovskite devices based on MAPbI 3 film obtained by this strategy produced optimized power conversion efficiency over 17% under only 5 min of IAA treatment, which increased by 2.6% compared to the thermal annealing. The efficiency improvement mainly attributed to better crystallinity, larger crystal grains under the IAA treatment, which had provided a new strategy for the future industrial production of perovskites.