Implications of Multichromophoric Arrays in Organic Photovoltaics

Abstract

A covalently linked multi-chromophoric array (BDP-Por) was used as the donor layer in planar hetero-junction organic photovoltaic (OPV) cells with the structure (ITO/BDPPor/C 60 /BCP//Al, BCP = bathocuproine). BDP-Por is a platinum tetrabenzoporphyrin core (Pt(TPBP)) bonded through the phenyl groups to the meso position of four 4,4-difluoro-3,5-dimethyl-4-bora-3a,4a-diaza-s-indacene (BODIPY) moieties. The OPV outperforms analogous OPVs which use only the Pt(TPBP) as the donor, predominantly by producing a higher short circuit current (J SC of 2.5 vs. 4.5 mA/cm 2 ), due to the enhanced absorptivity of the multi-chromophoric array. The open circuit voltages (V OC ) for Pt(TPBP) and BDP-Por based OPVs are both 0.65 volts. The system was further investigated by preparing and testing OPVs made from an analogous system with porphyrin and BODIPY components blended into a single homogeneous donor layer that absorbs similarly to the array. It is then found that the mixed system generates the same photocurrent as the array with a similar responsivity, but gives an unstable open circuit voltage that quickly degrades to 0.34 V. It is determined that the donor layer components undergo phase segregation at the interface upon illumination, resulting in the decreased voltage and highlighting an advantage of the multi-chromophoric array.

Improving Solar Cell Performance Using Quantum Dot Triad Charge-Separation Engines

“…18,32 For example, a tandem-layered QD triad solar cell structure was found to produce a 3.0% power conversion efficiency as compared to the 1.65% efficiency for a single-layer large band gap QD solar cell. 19 Multichromophore organic solar cells 33 were found to have short-circuit currents that changed from 2.5 to 4.5 mA/cm 2 when a donor platinum tetrabenzoporphyrin was linked to an organic dye acceptor with an unsaturated bridge. Molecular triad architectures were also shown to have larger ET yields than the yield found in molecular dyad systems.…”

“…Multilayered QD thin-film solar cells typically exhibit increased energy-conversion efficiencies compared to single-layer cells. ,,− The high efficiency of multilayered QD thin films is usually explained by the large short-circuit current that results from the large number of QD absorbers in the device. , For example, a tandem-layered QD triad solar cell structure was found to produce a 3.0% power conversion efficiency as compared to the 1.65% efficiency for a single-layer large band gap QD solar cell . Multichromophore organic solar cells were found to have short-circuit currents that changed from 2.5 to 4.5 mA/cm 2 when a donor platinum tetrabenzoporphyrin was linked to an organic dye acceptor with an unsaturated bridge. Molecular triad architectures were also shown to have larger ET yields than the yield found in molecular dyad systems. − In a trilayer organic solar cell, with an ET energy cascade but a flat valence band profile, an ∼2-fold increase in power conversion efficiency was observed.…”

Liquid PEG Polymers Containing Antioxidants: A Versatile Platform for Studying Oxygen-Sensitive Photochemical Processes

“…Three oxygen scavengers were selected here from a vast number of potential candidates, namely, oleic acid (OA), 9,10-dimethylanthracene (DMA), and 2,5-dimethylfuran (DMF). The upconversion system was based on the established red-absorbing triplet photosensitizer platinum­(II) tetraphenyltetrabenzoporphyrin (PtTPBP), synthesized as previously reported, in concert with the highly fluorescent blue/green emitter 9,10-bisphenylethynylanthracene (BPEA, Φ F = 0.94) (Figure ). ,,, Relevant triplet energy transfer parameters and upconversion metrics have been documented to determine the impact of the various components on the ultimate upconversion performance.…”

Solvent Thermodynamic Driving Force Controls Stacking Interactions between Polyaromatics

“…Organic semiconductors remain materials of interest in a wide array of fields in both fundamental and applied science. − This interest stems from the natural abundance of the elements used to synthesize these materials, as well as their novel physical properties found thus far only in organics, such as singlet fission. , Several research groups have demonstrated the ability to fabricate functional devices such as field-effect transistors, optoelectronic components, − and photovoltaic cells using solutions of organic semiconductors . While these solution-based approaches may offer lower costs in both dollars and energy than some of the more traditional approaches for inorganic materials, using a solvent carrier for the active molecular unit introduces a level of complexity to processing not encountered using other methods.…”