Akademik Veri Yönetim Sistemi
Diğer Ülkelerden Üniversiteler Tarafından Desteklenmiş Proje, 2017 - 2018
For DSSC the present state-of-the art devices are based on organic or porphyrine dyes with donor-p bridge-acceptor (D-p-A) structures together with Cobalt(II/III) complexes as redox shuttles. The fundamental limitations with the Co-complexes have been identified as an unnecessary high driving force for dye regeneration and diffusion limitations. In the proposed project we will use these materials as reference systems. For development of redox systems and hole transporting materials (HTM) in DSSC we will focus on our recent breakthrough using copper(I/II) complexes as redox couples. These electrolytes give record solar cell open circuit voltages due to the small internal potential drop for dye regeneration. A driving force of only 0.2V is sufficient for efficient dye regeneration, which can be compared with about 0.4V for Co-complexes and more than 0.5V for the conventional iodide-tri-iodide system. The low driving force for dye regeneration is the fundamental basis for our focus on this new redox system in the proposed project, making it possible to reach DSSC power conversion efficiencies (PCEs) above 15%. The Cu-complexes can also be prepared as redox melts, which will be explored as a novel type of redox system in DSSC. Unexpectedly, we also found that the Cu-complexes can work as a solid-state HTM. With the development in the on-going project of J-aggregates and methodologies to study charge transport in such systems by Prof. Frank Nuesch, EMPA, we have an excellent platform to investigate charge transfer and transport processes in the solid-state Cu-complex HTMs. To develop new dyes for DSSC requires a fundamental understanding of the charge dynamics of the best D-p-A dyes. In the new strategy that has been introduced in the design of organic dye sensitizers, the conjugated p-bridge acts not only as a channel for electron transfer from D to A moieties but also as an individual chromophore. Various diketopyrrolopyrrole (DPP) and porphyrine cores have been successfully developed into effective excitonic p-bridges. The exact role of the chromophore bridge in kinetic processes, has however, not been explored yet. We intend in collaboration with Prof. Jacques Moser to focus on the characterization of sensitized solar cells with inherently colored p-bridged sensitizers. The aim will be to provide significant insights into the dual function of excitonic p-bridges on device performance and to bring new fundamental knowledge on photoinduced charge transfer mechanisms and dynamics in such complex D-p-A-TiO2 systems. During the last 2 years we have together with the laboratory of Prof. Michael Grätzel made a large leap forward in the field of perovskite solar cells (PSCs). We achieved at the end of year 2015 a certified PCE of 21%. The general composition of the perovskite material is ABX3, where A is a monovalent cation, B stands normally for Pb and X represents a halide ion. Today’s best performing perovskite solar cells use mixtures of A and X ions. Although the current PCE is impressive, the open-circuit voltage (VOC) of these solar cells reaches at best 1.20V, which is lower than their theoretical limit of 1.32V. The loss of at least 120 mV arises from non-radiative recombination of photo-generated charge carriers and manifests itself in a low external quantum yield for electroluminescence. One important goal of our investigation is thus to reduce the non-radiative recombination of charge carriers since this will pave the way to reach higher VOC and hence higher efficiency values. This will be done by scrutinizing the specific features of the mixed A-cation/mixed X-anion perovskite materials as light harvesters. The key role played by the nature of the interface formed between the electron and hole extraction layer with the perovskite light harvester in the photo-conversion process will also be elucidated in detail. The on-going project includes 4 PhD students and the present proposal will guarantee the continuation of the PhD work of all the students.