High-Performance Polymer Solar Cell with Single Active Material of Fully Conjugated Block Copolymer Composed of Wide-Band gap Donor and Narrow-Band gap Acceptor Blocks

Abstract

We synthesized a novel fully conjugated block copolymer, P3, in which a wide-band gap donor block (P1) was connected to a narrow-band gap acceptor block (P2). As P3 contains P1 block with a wide bandgap and P2 block with a narrow bandgap, it exhibits a very wide complementary absorption. Transient photoluminescence measurement using P3 dilute solution demonstrated intramolecular charge transfer between the P1 block and the P2 block, which was not observed in a P1/P2 blend solution. A P3 thin film showed complete PL quenching because the photoinduced inter-/intramolecular charge transfer states were effectively formed. This phenomenon can play an important role in the photovoltaic properties of P3-based polymer solar cells. A single active material polymer solar cell (SAMPSC) fabricated from P3 alone exhibited a high power conversion efficiency (PCE) of 3.87% with a high open-circuit voltage of 0.93 V and a short-circuit current of 8.26 mA/cm, demonstrating a much better performance than a binary P1-/P2-based polymer solar cell (PCE = 1.14%). This result facilitates the possible improvement of the photovoltaic performance of SAMPSCs by inducing favorable nanophase segregation between p- and n blocks. In addition, owing to the high morphological stability of the block copolymer, excellent shelf-life was observed in a P3-based SAMPSC compared with a P1/P2-based PSC.

A Global View on Block Copolymers

“…A deep look into current investigations makes us speculate on the potential held by some hot papers. In particular, we would like to envisage a bright future for applicative challenges concerning the integration of specific block copolymers into large-scale manufacturing, namely in (i) all-polymer solar cells by fully conjugated donor-acceptor block copolymers [58], (ii) soft-solid electrolytes, as in micellar ion gels for self-healing electrochemical devices [59], (iii) nanofiltration membranes [60], and for the fabrication of (iv) N-and S-doped nanostructured carbons useful in adsorption, catalysis, and energy storage [57] or (v) nanoelectronic devices, e.g., through the optimization of infiltration techniques to be inserted into semiconductor fabrication processing [61]. Moreover, as recently discussed in a more general essay by Binder [62], additional strength to block copolymer synthesis investigations could come from the development of methodology mimicking biological systems, e.g., through the use of enzymes in enzymatic ATRP, or from a deeper tuning of "click" reactions to link large and voluminous molecules.…”

The Dawn of Single Material Organic Solar Cells

“…Very recently, Choi, and co‐workers reported another example of conjugated non‐P3HT‐based copolymer. In this work, a wide bandgap donor block of DTBDT–thiophenecarboxylate is connected to a narrow bandgap naphthalenediimide–selenophene acceptor block in order to obtain a wide complementary absorption ( 18 ) . The copolymer was synthesized by Stille coupling of oligomeric blocks of the D and A components.…”

Covalently linked donor–acceptor dyad for efficient single material organic solar cells

“…A PCE of 3.9% has been reached with alternating benzodithiophene donor and naphthalene diimide acceptor blocks, which self-assemble into a lamellar morphology. 9 Monodisperse oligomers have proven certain advantages over polymers, 10 thus, oligomeric D-A systems were implemented into SMOSCs. A PCE of 2.7% was reached for a perylene diimide, which was linked -as in the 'double cable' approach for polymers-via a flexible linker to a complex co-oligomeric donor consisting of fluorene, bithiophene, and benzothiadiazole moieties.…”

“…However, a lower PCE of 1.8% was obtained. 12 The topic of SMOSCs is scientifically highly interesting because it is still unclear, how the fundamental physical elementary processes such as exciton formation, diffusion, dissociation, polaron formation, and charge transport, which are well investigated for biphasic BHJSCs, 9 proceed in the small-sized D-A molecules and aggregates concomitant with the question, how the crucial phase-separated morphology and the D-A interfaces are formed. In particular, it is surprising that geminate recombination of charges is not the overall process.…”