Boron Subphthalocyanines and Silicon Phthalocyanines for Use as Active Materials in Organic Photovoltaics

Abstract

Organic photovoltaics (OPVs) have experienced continued interest over the last 25 years as a viable technology for the generation of power. Phthalocyanines are among the oldest commercial dyes and have been utilized in some of the earliest examples of OPVs. In recent years, the use of boron subphthalocyanines (BsubPcs) and silicon phthalocyanines (SiPcs) has attracted a flurry of interest with some examples of fullerene‐free devices reaching power conversion efficiencies >8 %. Unlike other more common divalent phthalocyanines such as copper or zinc, BsubPcs and SiPcs contain additional axial groups that can easily be functionalized without significantly affecting the optoelectronic properties of the macrocycle. This handle facilitates our ability to tune the solid‐state arrangement and other physical characteristics such as solubility ultimately giving us the ability to improve the thin film processing and final device performance. This review covers recent studies on the development of BsubPcs and SiPcs for use as active materials in organic photovoltaics.

Hexachlorinated Boron(III) Subphthalocyanine as Acceptor for Organic Photovoltaics: A Brief Overview

“…The interface gap E G of 1.95 eV was derived from soft XPS and XAS, with the use of DFT ( Table 1) [21]. This value of E G is much greater than what is attainable through pairing the SubPc donor with the conventional N-type acceptor C 60 , which explains the popularity of Cl 6 SubPc among the so-called "non-fullerene" acceptors for organic photovoltaics [5,16,17,21,25,27,30,32,33]. The DFT calculations on a Cl 6 SubPc molecule were also performed in Refs.…”

“…Cl 6 SubPc can be used in both-Refs. [5, 18-23, 25, 28-30, 35] and [5,6,27,33], respectively. Such flexibility is accounted for by the increased, as compared to phthalocyanines, solubility of Cl 6 SubPc, and subphthalocyanines in general, although a rigorous study of 1 Hexachlorinated Boron(III) Subphthalocyanine as Acceptor for Organic Photovoltaics: A Brief… DOI: http://dx.doi.org/10.5772/intechopen.90292 the solvation processes does not permit unambiguous attribution of conventional SubPc to the classical dyes, it is pigment-like rather [26,37].…”

“…Other data collections describing the performances of variously designed photovoltaic devices based on SubPc-type compounds can also be found in Refs. [1,4,5,28,64].…”

“…The thin film electronic devices utilizing both subphthalocyanines and diverse phthalocyanine-type compounds are traditionally classified as organic light-emitting diodes (OLEDs), organic field-effect transistors (OFETs), and organic photovoltaic cells (OPVC) [1,[4][5][6][7]. Of course, these fascinating heterocyclic molecules find their way into other areas of application such as resistive memory or molecular switches [8,9], but those are incomparably inferior to the above three types of thin film devices in terms of practical achievements.…”

“…We therefore will discuss SubPcs only from the viewpoint of their behavior in thin film photovoltaic cells, particularly in cells with an organic or hybrid heterojunction based on the hexachlorinated subphthalocyanine derivative Cl 6 SubPc (Figure 1). This compound is gaining practical importance, though many other peripherally halogen-substituted SubPc derivatives have been synthesized over the last decade [1][2][3][4][5]16]. To the best of our knowledge, only one hexachlorinated derivative with an extraligand other than chlorine was used in a photovoltaic cell [17].…”