Title:	Charge-transport mechanisms in organic, metal-organic and inorganic hole- and electron-transport materials
DNr:	SNIC 2020/5-66
Project Type:	SNIC Medium Compute
Principal Investigator:	Lars Kloo <lakloo@kth.se>
Affiliation:	Kungliga Tekniska högskolan
Duration:	2020-02-01 – 2021-02-01
Classification:	10499 10403 10407
Homepage:	https://www.kth.se/sv/che
Keywords:

Abstract

In order for new light-absorbing to work optimally in solar cell devices, they need to be sandwiched between electron- and hole-capturing materials that reduce recombination losses significantly. In perovskite solar cells such materials can boost power conversion efficiencies from <5% to >20%. However, very little is known about the central charge-transfer mechanisms from the light-absorbing material to the surrounding materials, as well as the transport in the materials themselves. This project aims to build relevant models of the materials as well as materials interfaces. Input will consist of interface modelled using in-house classical and ab initio molecular dynamics transferred for more detailed studies at preferably DFT level. The materials and interface models necessary will inevitable become too large to allow efficient studies using our in-house resources. For one of the major project, recently, we reported polymatic, cost-effective, dopant-free hole transport materials for efficient and stable perovskite solar cells (J. Am. Chem. Soc. 2019, 141, 50, 19700-19707). A stabilized power conversion efficiency (PCE) of 20.3% and remarkably enhanced device longevity are achieved using the dopant-free polymer P3 with a low concentration of 5 mg/mL, qualifying the device as one of the best PSC systems constructed on the basis of dopant-free HTMs so far. Adequate experiments were done to characterize the properties, and prove the good function of the new material. However, the crystal structue is still unavailable and the spatial stacking mode of the molecules is unknown yet, as well as the hole/charge transfer mechanism under the current experimental conditions. However, theoretical tools can provide a useful way to understanding on the molecular level. We plan to find the operation mechanism of hole/charge transfer and why the materials can reap the benefits from substituting florides into the sidechains. This will be highly useful insights for future design of new and efficient hole-transport materials. In practice, the adequent models for the materials are based on a number of repeated units of the polymer, and the number should be sufficiently high to simulate the nature of the materials. Thus the computational cost will be very high to generate fully converged results. The NSC has well-known efficient and powerful computation resources, which would facilitate our calculations.