A method to detect triplet exciton transfer from singlet fission materials into silicon solar cells: Comparing different surface treatments.

Benjamin Daiber,Moritz H Futscher,Stefan L Luxembourg,Steven Verboom,Bruno Ehrler,Sidharam P Pujari,Stefan W Tabernig,Jumin Lee,Han Zuilhof

doi:10.1063/1.5139486

Abstract

Singlet fission is one of the most promising routes to overcome the single-junction efficiency limit for solar cells. Singlet fission-enhanced silicon solar cells are the most desirable implementation, but transfer of triplet excitons, the product of singlet fission, into silicon solar cells has proved to be very challenging. Here, we report on an all optical measurement technique for the detection of triplet exciton quenching at semiconductor interfaces, a necessary requirement for triplet exciton or charge transfer. The method relies on the growth of individual, single-crystal islands of the singlet fission material on the silicon surface. The islands have different heights, and we correlate these heights to the quenching efficiency of triplet excitons. The quenching efficiency is measured by spatially resolved delayed fluorescence and compared to a diffusion-quenching model. Using silicon capped with a blocking thermal oxide and aromatic monolayers, we demonstrate that this technique can quickly screen different silicon surface treatments for triplet exciton quenching.

Highlights

The efficiency of silicon solar cells is already very close to its theoretical limit,1 which drives the search for new concepts to increase power conversion efficiency
To tandem solar cells, singlet fission has emerged as a promising route to allow for higher efficiency,2 with comparably simple implementation in solar cell devices and spectral stability under the changing environmental conditions
One implementation where singlet fission enhances the current of a silicon solar cell relies on a tandem cell configuration

Summary

Introduction

The efficiency of silicon solar cells is already very close to its theoretical limit,1 which drives the search for new concepts to increase power conversion efficiency. It would be more elegant to directly transfer triplet excitons into silicon, which would not require any changes to the contacts of a conventional silicon solar cell. A necessary requirement for the transfer of triplet exciton energy or charge is the quenching of the triplet exciton at the organic/silicon interface.

Results

Conclusion