Proceedings of nanoGe Fall Meeting19 (NFM19)
DOI: https://doi.org/10.29363/nanoge.nfm.2019.262
Publication date: 18th July 2019
The energetic offset between the initial photoexcited state and charge-transfer (CT) state in organic heterojunction solar cells influences both charge generation and open-circuit voltage (Voc). In this work, we use time-resolved spectroscopy and voltage loss measurements to analyse the effect of the exciton-CT state offset on charge transfer, separation and recombination processes in chemically similar blends of a low-bandgap isoindigoid polymer (INDT-S) with fullerenes derivatives of different electron affinity (PCBM and KL). The two blends possess large offsets for hole transfer, but different offsets for electron transfer: a very low offset for the INDT-S:PCBM blend and a higher one for the INDT-S:KL blend. In the case of the lower exciton-CT state offset (INDT-S:PCBM), the photocurrent generation is lower, Voc is higher and non-radiative voltage losses are lower than in INDT-S:KL. By characterising the dynamics of the devices after photoexcitation using both transient absorption spectroscopy (TAS) and pump push photocurrent (PPPC) , we find that the dynamics of the INDT-S:PCBM blend shows different excited state dynamics depending on whether the donor or acceptor is photoexcited. Interestingly, the charge recombination dynamics in INDT-S:PCBM are distinctly faster than in INDT-S:KL upon excitation of the donor. We reconcile these observations using a model for the dependence of Voc on radiative and non-radiative recombination. We also explain the effect of exciting donor or acceptor on charge transfer and recombination using a simple kinetic model. The results of the model show that hybridisation between the lowest excitonic and CT states can significantly reduce Voc losses whilst still allowing reasonable charge generation efficiency.
nanoGe is a prestigious brand of successful science conferences that are developed along the year in different areas of the world since 2009. Our worldwide conferences cover cutting-edge materials topics like perovskite solar cells, photovoltaics, optoelectronics, solar fuel conversion, surface science, catalysis and two-dimensional materials, among many others.
Previously nanoGe Spring Meeting (NSM) and nanoGe Fall Meeting (NFM), MATSUS is a multiple symposia conference focused on a broad set of topics of advanced materials preparation, their fundamental properties, and their applications, in fields such as renewable energy, photovoltaics, lighting, semiconductor quantum dots, 2-D materials synthesis, charge carriers dynamics, microscopy and spectroscopy semiconductors fundamentals, etc.
International Conference on Hybrid and Organic Photovoltaics
International Conference on Hybrid and Organic Photovoltaics (HOPV) is celebrated yearly in May. The main topics are the development, function and modeling of materials and devices for hybrid and organic solar cells. The field is now dominated by perovskite solar cells but also other hybrid technologies, as organic solar cells, quantum dot solar cells, and dye-sensitized solar cells and their integration into devices for photoelectrochemical solar fuel production.
Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
The main topics of the Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics (IPEROP) are discussed every year in Asia-Pacific for gathering the recent advances in the fields of material preparation, modeling and fabrication of perovskite and hybrid and organic materials. Photovoltaic devices are analyzed from fundamental physics and materials properties to a broad set of applications. The conference also covers the developments of perovskite optoelectronics, including light-emitting diodes, lasers, optical devices, nanophotonics, nonlinear optical properties, colloidal nanostructures, photophysics and light-matter coupling.
The International Conference on Perovskite Thin Film Photovoltaics Perovskite Photonics and Optoelectronics (NIPHO) is the best place to hear the latest developments in perovskite solar cells as well as on recent advances in the fields of perovskite light-emitting diodes, lasers, optical devices, nanophotonics, nonlinear optical properties, colloidal nanostructures, photophysics and light-matter coupling.