Microphase‐Separated Donor–Acceptor Diblock Copolymers: Influence of HOMO Energy Levels and Morphology on Polymer Solar Cells

Abstract

The synthesis of novel semiconducting donor–acceptor (D–A) diblock copolymers by means of nitroxide‐mediated polymerization (NMP) is reported. The copolymers contain functional moieties for hole transport, electron transport, and light absorption. The first block, representing the donor, is made up of either substituted triphenylamines (poly(bis(4‐methoxyphenyl)‐4′‐vinylphenylamine), PvDMTPA) or substituted tetraphenylbenzidines (poly(N,N′‐bis(4‐methoxyphenyl)‐N‐phenyl‐N′‐4‐vinylphenyl‐(1,1′‐biphenyl)‐4,4′‐diamine), PvDMTPD). The second block consists of perylene diimide side groups attached to a polyacrylate backbone (PPerAcr) via a flexible spacer. This block is responsible for absorption in the visible range and for electron‐transport properties. The electrochemical properties of these fully functionalized diblock copolymers, PvDMTPA‐b‐PPerAcr and PvDMTPD‐b‐PPerAcr, are investigated by cyclic voltammetry (CV), and their morphology is investigated by transmission electron microscopy (TEM). All diblock copolymers exhibit microphase‐separated domains in the form of either wire‐ or wormlike structures made of perylene diimide embedded in a hole‐conductor matrix. In single‐active‐layer organic solar cells, PvDMTPD‐b‐PPerAcr reveals a fourfold improvement in power conversion efficiency (η = 0.26 %, short‐circuit current (ISC) 1.21 mA cm–2), and PvDMTPA‐b‐PPerAcr a fivefold increased efficiency (η = 0.32 %, ISC = 1.14 mA cm–2) compared with its unsubstituted analogue PvTPA‐b‐PPerAcr (η = 0.065 %, ISC = 0.23 mA cm–2).

Single Material Solar Cells: the Next Frontier for Organic Photovoltaics?

“…[ 64 ] Replacement of the triphenylamine donor unit by stronger donor groups in copolymers 18 and 19 led to a signifi cant improvement of the performances and the resulting SMOCs showed J sc values higher than 1.0 mA cm − 2 and effi ciencies of 0.32 and 0.26%. [ 65 ] More recently the same group has synthesized a copoly mer based on poly(3-hexylthiophene) as donor group and perylene-diimide acrylate as acceptor ( 20 ) and observed specifi c …”

Nanoscale structure of solar cells based on pure conjugated polymer blends

“…55 Attempts to exploit donor-acceptor block copolymers for photovoltaic applications have been limited, both in number and success. [56][57][58][59][60] Another way to make the blend morphology less sensitive to the film forming conditions was introduced by Kietzke and co-workers. 61 The method involves Figure 4.…”

A New Supramolecular Route for Using Rod‐Coil Block Copolymers in Photovoltaic Applications

“…[14][15][16][17][18][19] Block copolymers composed of an electron-donating and an electronaccepting block are therefore particularly interesting for PV applications and are presently studied worldwide by several research groups. [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] Particularly, rod-coil block copolymers using poly[(2,5-di(2-ethyl)hexyloxy)-1,4-phenylenevinylene] (DEH-PPV) as electron donor and various coil blocks (such as polystyrene or polybutylacrylate) with covalently linked fullerene moieties as electron acceptor have been investigated intensively. [23][24][25][26][27][28] Although these studies have given considerable insight into the physics of copolymer self-assembly, their efficient utilization as the active layer in PV devices has not yet been fully demonstrated.…”