A Selenophene Analogue of PCDTBT: Selective Fine-Tuning of LUMO to Lower of the Bandgap for Efficient Polymer Solar Cells

Abstract

In an attempt to further improve the performance of the PCDTBT-based polymer solar cells (PSCs), we have synthesized a selenophene analogue of PCDTBT, namely, PCDSeBT, in which diselenienylbenzothiadiazole (DSeBT) monomer alternately flanks with a 2,7-carbazole unit. The intrinsic properties of PCDSeBT are not only characterized by UV–vis absorption, cyclic voltammetry (CV), and organic field-effect transistors (OFETs) but also the surface morphology, mobilities of space charge-limited current (SCLC) model, and polymer solar cells (PSCs) in its bulk-heterojunction (BHJ) active layer with [6,6]-phenyl C71-butyric acid methyl ester (PC71BM) are evaluated in detail. It is found that PCDSeBT simultaneously has a low-lying highest occupied molecular orbital (HOMO) energy level at −5.4 eV and a low bandgap of 1.70 eV as required by the ideal polymers for BHJ PSCs. The high current of 11.7 mA/cm2 is obtained for PCDSeBT-based PSCs, to our knowledge, which is among the highest short-circuit current density (J SC ) values obtained from a BHJ device consisting of PCDTBT derivatives and [6,6]-phenyl C61-butyric acid methyl ester (PCBM). The high J SC value, along with a moderate fill factor (FF) of 45% and a high open-circuit voltage (V OC ) of 0.79 V, yields a power conversion efficiency (PCE) of 4.12%, which is about 37% increase in PCE from a PCDTBT-based reference device. On the basis of our results, one can be concluded that the DSeBT placement for construction of donor (D)-acceptor (A) polymers is an easy and effective way to realize both the higher J SC and V OC values in PSCs, as a consequence of the selective lower-lying lowest unoccupied molecular orbital (LUMO) with the HOMO being almost unchanged, together with the effective broadening on the absorption band.

High‐Mobility Naphthalene Diimide and Selenophene‐Vinylene‐Selenophene‐Based Conjugated Polymer: n‐Channel Organic Field‐Effect Transistors and Structure–Property Relationship

“…[43][44][45][46] Such a path has led various research groups to demonstrate high-mobility p-channel conjugated polymers with improved ambient stability. [44,[47][48][49][50][51] Despite the strong interest in the incorporation of selenophenes in p-channel conjugated polymers, their use in n-channel and/or ambipolar polymers has been quite limited so far. [52] While the chemical structure of the polymer semiconductor is of fundamental importance in determining the optoelectronic properties of a material, it is also very well known that in the solid state the film morphology and the packing motif of the conjugated segments critically size the charge transport properties.…”

Two new fluorinated copolymers based on thieno[2,3-f]benzofuran for efficient polymer solar cells

“…The related optical parameters for two copolymers are summarized in Table 2. 36 The thin-film absorption exhibit similar optical property to that in solution. In dilute CHCl 3 solution, TBFPF-BT and TBFPF-BO display two well-defined main absorption peaks, one intense band at higher energies covers from 350 to 450 nm resulting from π-π* transitions and the other one at lower energies range from 500 to 700 nm which should be attributed to intramolecular charge transfer (ICT) between donor and acceptor units in the copolymer backbone.…”

An amorphous N-type polymer based on perylenediimide and selenophene for all-polymer solar cells application

“…At the same time, selenophene-bearing polymers showed enhanced planarity and extended conjugation length due to its less aromaticity [14][15][16][17][18][19]. The substitution of selenophene also showed superior performances over the thiophene analogs in n-type photovoltaic polymers [20,21].…”