Non-Fullerene Acceptor-Based Solar Cells: From Structural Design to Interface Charge Separation and Charge Transport.

Runzhou Su,Qungui Wang,Yuanzuo Li,Yanhui Yang,Peng Song,Fengcai Ma

doi:10.3390/polym9120692

Abstract

The development of non-fullerene small molecule as electron acceptors is critical for overcoming the shortcomings of fullerene and its derivatives (such as limited absorption of light, poor morphological stability and high cost). We investigated the electronic and optical properties of the two selected promising non-fullerene acceptors (NFAs), IDIC and IDTBR, and five conjugated donor polymers using quantum-chemical method (QM). Based on the optimized structures of the studied NFAs and the polymers, the ten donor/acceptor (D/A) interfaces were constructed and investigated using QM and Marcus semi-classical model. Firstly, for the two NFAs, IDTBR displays better electron transport capability, better optical absorption ability, and much greater electron mobility than IDIC. Secondly, the configurations of D/A yield the more bathochromic-shifted and broader sunlight absorption spectra than the single moiety. Surprisingly, although IDTBR has better optical properties than IDIC, the IDIC-based interfaces possess better electron injection abilities, optical absorption properties, smaller exciton binding energies and more effective electronic separation than the IDTBR-based interfaces. Finally, all the polymer/IDIC interfaces exhibit large charge separation rate (KCS) (up to 1012–1014 s−1) and low charge recombination rate (KCR) (<106 s−1), which are more likely to result in high power conversion efficiencies (PCEs). From above analysis, it was found that the polymer/IDIC interfaces should display better performance in the utility of bulk-heterojunction solar cells (BHJ OSC) than polymer/IDTBR interfaces.

Highlights

With the exhaustion of fossil fuel and the sustained environmental pollution, seeking new sustainable and clean energy is imminent
Based on the optimized ground-sated structures of non-fullerene acceptors (NFAs) and the five polymers, we studied the ten D/A interfaces, which include the two synthesized D/A interfaces (P-BZS/IDIC and PDBT-T1/IDIC) and eight newly designed
The results demonstrated that: (a) As the substitution of fullerene derivatives, the lowest unoccupied molecular orbitals (LUMOs) of the two NFAS are all higher than that of PCMB, which can enhance the value of VOC > (b) Among the five polymers, PDBT-T1 has largest absorption peak in the visible region, and polymers

Summary

Introduction

With the exhaustion of fossil fuel and the sustained environmental pollution, seeking new sustainable and clean energy is imminent. Organic solar cell (OSC) is the core device for converting solar energy into electric energy, and bulk-heterojunction (BHJ) polymer solar cells play an important role in many solar cell devices [1,2,3]. Polymer solar cells (PSCs) have attracted much attention because of their own advantages such as being a low-cost, flexible, and lightweight material, and having a large-area fabrication [4,5,6,7]. The active layer is a key part of the heterojunction solar cell, which typically consists of the electronic donor and electronic acceptor materials, installing into a bilayer structure or in the form of a blend [8], and the volume density of organic active layer has direct influence on organic photovoltaics (OPV) performance [8].

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