A calorimetric approach to reach high performance perovskite solar cells

• Revealed thermal transitions in the perovskite layer during crystallization.
• DSC is a comprehensive tool to determine optimal perovskite crystallization.
• Low formation energies of CH3NH3PbI3−xClx implies feasible material formation and degradation.

Perovskite solar cells (PSCs) have emerged as an alternative photovoltaic technology reaching record certified efficiencies of 20.1% in only 6 years. Film morphology and crystalline structure of the perovskite are crucial factors to determine the final photovoltaic performance. In this work, the thermal transitions occurring during the crystallization of the CH3NH3PbI3−xClx perovskite were revealed by differential scanning calorimetry (DSC). Particularly, the calorimetric analysis suggest that an annealing temperature around 130 °C drives to better ordered perovskite structures as confirmed by X-ray diffraction (XRD) analysis. Indeed, the photovoltaic performance of the devices developed at such optimal temperature reached 8.7% average PCE which is in the state-of-the-art for the considered pin planar PSC. Our experimental observations highlight the relevance of DSC as a powerful tool to determine in situ the CH3NH3PbI3−xClx optimal crystallization conditions. This analysis provides a better understanding of the physical processes occurring during the perovskite crystallization and has the potential to be applied in the optimization of novel photovoltaic materials and structures.

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