High internal quantum efficiency in fullerene solar cells based on crosslinked polymer donor networks

Abstract

The power conversion efficiency of organic photovoltaic cells depends crucially on the morphology of their donor–acceptor heterostructure. Although tremendous progress has been made to develop new materials that better cover the solar spectrum, this heterostructure is still formed by a primitive spontaneous demixing that is rather sensitive to processing and hence difficult to realize consistently over large areas. Here we report that the desired interpenetrating heterostructure with built-in phase contiguity can be fabricated by acceptor doping into a lightly crosslinked polymer donor network. The resultant nanotemplated network is highly reproducible and resilient to phase coarsening. For the regioregular poly(3-hexylthiophene):phenyl-C61-butyrate methyl ester donor–acceptor model system, we obtained 20% improvement in power conversion efficiency over conventional demixed biblend devices. We reached very high internal quantum efficiencies of up to 0.9 electron per photon at zero bias, over an unprecedentedly wide composition space. Detailed analysis of the power conversion, power absorbed and internal quantum efficiency landscapes reveals the separate contributions of optical interference and donor–acceptor morphology effects.

Reactive & Efficient: Organic Azides as Cross-Linkers in Material Sciences

“…Because crosslinking renders the polymer film insoluble in the CB, a subsequent top acceptor layer could be solution deposited from the same solvent. The crosslinked device showed 20% improvement in PCE over conventional devices [8,59]. Similar results were obtained using bisazide 1,6-diazidohexane (DAZH) in combination with a polysilaindacenodithiophene-benzothiadiazole and (6,6)-phenyl-C 71 -butyric acid methyl ester (SiIDT-BT/PC 71 BM) blend.…”

“…In recent years, this process has also proven to be a powerful strategy to boost efficiencies of polymer-based devices such as membrane fuel cells, organic solar cells (OSCs), light-emitting diodes (LEDs), and organic field-effect transistors (OFETs). For example, the morphology of the donor and acceptor material in bulk hetero junction organic solar cells was successfully locked and the long-time stability of the device increased in this way [8]. Due their superior crosslinking efficiency and mild activation methods devoid of the addition of initiators, organic azides have become the compounds of choice in these applications.…”

Quantum Chemical Studies of Endofullerenes (M@C60) Where M = H2O, Li+, Na+, K+, Be2+, Mg2+, and Ca2+

“…Since the discovery of C 60 [1], the literature has reported the development of sev-eral fullerene derivatives based on the functionalization of the C 60 cage aiming to produce new properties and/or improve their existing properties. Other important studies involve the use of C 60 derivatives in biological systems [2]- [4], solar cells [5]- [8] and superconductors [9]- [11]. Another class of C 60 derivatives has been achieved by the encapsulation of small molecules, metals and ions inside the C 60 cage.…”

Universal three-dimensional crosslinker for all-photopatterned electronics

“…Moreover, the thermal stability of the materials would be enhanced because of their crosslinked structure. Accordingly, photocrosslinking agents, such as bifunctional organic azides, have been developed [27][28][29] , and electronic devices employing these layers have been demonstrated 6,[30][31][32][33][34][35][36][37] . To the best of our knowledge, however, patterning and stacking of multiple functional materials by consecutive application of photocrosslinking processes have not yet been attempted.…”