Browsing by Autor "Juan Felipe Montoya"

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Catalytic role of bridging oxygens in TiO2 liquid phase photocatalytic reactions: analysis of H216O photooxidation on labeled Ti18O2
(Royal Society of Chemistry, 2017) Juan Felipe Montoya; Detlef W. Bahnemann; Pedro Salvador; José Peral
TiO2 surface lattice oxygens are actively involved in the photocatalytic oxidation of water as demonstrated by isotopic tracing experiments with Ti18O2.
Low organic content hybrid perovskite (Cs1-xDMAx)Pb(Br1-xIx)3 with increased stability for solar cell fabrication
(National University of Colombia, 2023) Juan J. Patiño; Juan Felipe Montoya; Edwin Alexander Ramírez; Franklin Jaramillo; Daniel Ramírez
Hybrid perovskites with reduced organic content have brought great interest for solar cells applications. Particularly, adding inorganic cations increase material stability, by providing an adequate tolerance factor. However, these cations lead to lower absorption coefficient than using only organic cations, therefore it is necessary to implement strategies for having films with appropriate thickness and good light absorption properties. In this work, several experiments were performed with ((Cs1-xDMAx)Pb(Br1-xIx)3 perovskite films of different thicknesses, resulting in devices with photovoltaic conversion efficiency (PCE) near 80% of the reference MAPbI3 cell, high purity phase, appropriate morphology, and higher stability. The perovskite successfully maintained integrity for 12 days in air with relative humidity between 30 and 40%, indicating the fulfillment of the study's objectives.
Optimization of the Ag/PCBM interface by a rhodamine interlayer to enhance the efficiency and stability of perovskite solar cells
(Royal Society of Chemistry, 2017) John Ciro; Santiago Mesa; José Ignacio Uribe; Mario Alejandro Mejía Escobar; Daniel Ramírez; Juan Felipe Montoya; Rafael Betancur; Hyun-Seok Yoo; Nam‐Gyu Park; Franklin Jaramillo
Effective control of the interface between the metal cathode and the electron transport layer (ETL) is critical for achieving high performance p-i-n planar heterojunction perovskite solar cells (PSCs). Several organic molecules have been explored as interlayers between the silver (Ag) electrode and the ETL for the improvement in the photovoltaic conversion efficiency (PCE) of p-i-n planar PSCs. However, the role of these organic molecules in the charge transfer at the metal/ETL interface and the chemical degradation processes of PSCs has not yet been fully understood. In this work, we systematically explore the effects of the interfacial modification of the Ag/ETL interface on PSCs using rhodamine 101 as a model molecule. By the insertion of rhodamine 101 as an interlayer between Ag and fullerene derivatives (PC60BM and PC70BM) ETLs improve the PCE as well as the stability of p-i-n planar PSCs. Atomic force microscopy (AFM) characterization reveals that rhodamine passivates the defects at the PCBM layer and reduces the band bending at the PCBM surface. In consequence, charge transfer from the PCBM towards the Ag electrode is enhanced leading to an increased fill factor (FF) resulting in a PCE up to 16.6%. Moreover, rhodamine acts as a permeation barrier hindering the penetration of moisture towards the perovskite layer as well as preventing the chemical interaction of perovskite with the Ag electrode. Interestingly, the work function of the metal cathode remains more stable due to the rhodamine incorporation. Consequently, a better alignment between the quasi-Fermi level of PCBM and the Ag work function is achieved minimizing the energy barrier for charge extraction. This work contributes to reveal the relevance of proper interfacial engineering at the metal-cathode/organic-semiconductor interface.