Porphyrin‐Based Bulk Heterojunction Organic Photovoltaics: The Rise of the Colors of Life

Abstract

Organic photovoltaics (OPV) represent a thin‐film PV technology that offers attractive prospects for low‐cost and aesthetically appealing (colored, flexible, uniform, semitransparent) solar cells that are printable on large surfaces. In bulk heterojunction (BHJ) OPV devices, organic electron donor and acceptor molecules are intimately mixed within the photoactive layer. Since 2005, the power conversion efficiency of said devices has increased substantially due to insights in the underlying physical processes, device optimization, and chemical engineering of a vast number of novel light‐harvesting organic materials, either small molecules or conjugated polymers. As Nature itself has developed porphyrin chromophores for solar light to energy conversion, it seems reasonable to pursue artificial systems based on the same types of molecules. Porphyrins and their analogues have already been successfully implemented in certain device types, notably in dye‐sensitized solar cells, but they have remained largely unexplored in BHJ organic solar cells. Very recent successes do show, however, the strong (latent) prospects of porphyrinoid semiconductors as light‐harvesting and charge transporting materials in such devices. Here, an overview on the state‐of‐the‐art of porphyrin‐based solution‐processed BHJ OPV is provided and insights are given into the pathways to follow and hurdles to overcome toward further improvements of porphyrinic materials and devices.

Spectral-Luminescent Properties of meso-Tetraarylporphyrins Revisited: The Role of Aryl Type, Substitution Pattern and Macrocycle Core Protonation

“…[38] The attachment of the second proton to Ph 4 was found to be energetically comparable to the first protonation step, instead of being significantly less favorable as in the case of Mes 4 . The second proton attachment to Ph 4 is facilitated by the interplay between the tilting of the pyrrolenine ring to be protonated and a pronounced electrostatic binding spot at the protonation site (the nitrogen atom of the pyrrolenine ring).…”

“…The family of meso-tetraarylporphyrins, with its most notable example 5,10,15,20-tetraphenylporphyrin or TPP (hereafter referred to as Ph 4 to provide a clear structurerelated notation allowing easy comparison of all compounds studied in this work), gathers the most frequently occurring synthetic porphyrins. These compounds are widely used in the design of artificial models of naturally occurring porphyrin chromophores, [1,2] as key structures of high performance photoactive compounds in dye-sensitized and bulk heterojunction organic solar cells, [3,4] as photosensitizers in photodynamic (cancer) therapy (PDT) and in antibacterial therapy, [5] being the "heart" of a huge diversity of supramolecular systems of different complexity and destination.…”

“…These compounds are widely used in the design of artificial models of naturally occurring porphyrin chromophores, [1,2] as key structures of high performance photoactive compounds in dye-sensitized and bulk heterojunction organic solar cells, [3,4] as photosensitizers in photodynamic (cancer) therapy (PDT) and in antibacterial therapy, [5] being the "heart" of a huge diversity of supramolecular systems of different complexity and destination. [1,6] The popularity of 5,10,15,20-tetraarylporphyrins arises from their well-developed and straightforward syntheses and the availability of a wide variety of aryl-functionalized derivatives.…”

“…Being almost indistinguishable in their free base (FB) forms, no similarity remains upon protonation of these porphyrins. Whereas the sequential formation of monoprotonated (MP) and diprotonated (DP) species is documented for Mes 4 , [36] the diprotonated form of Ph 4 appears in a single step involving the simultaneous attachment of two protons, [10] with special efforts needed to stabilize the monoprotonated form. [37] The mechanism of porphyrin basicity control by the meso-…”

Hybrid Mn-Porphyrin-Nanogold Nanomaterial Applied for the Spectrophotometric Detection ofβ-Carotene

“…e major peak of Mn-porphyrin is located at 477 nm, the highest intensity of the gold plasmon is positioned at 525 nm, and the plasmonic band of the MnTTPCl/n-Au hybrid is strongly bathochromically shifted to 590 nm, widening in the wavelength range of 480-750 nm and manifesting a hyperchromic e ect. ese three features of the hybrid nanomaterial recommend it for optoelectronic applications [39].…”