Optimized Active Layer Morphologies via Ternary Copolymerization of Polymer Donors for 17.6 % Efficiency Organic Solar Cells with Enhanced Fill Factor

Abstract

Regulating molecular structure to optimize the active layer morphology is of considerable significance for improving the power conversion efficiencies (PCEs) in organic solar cells (OSCs). Herein, we demonstrated a simple ternary copolymerization approach to develop a terpolymer donor PM6‐Tz20 by incorporating the 5,5′‐dithienyl‐2,2′‐bithiazole (DTBTz, 20 mol%) unit into the backbone of PM6 (PM6‐Tz00). This method can effectively tailor the molecular orientation and aggregation of the polymer, and then optimize the active layer morphology and the corresponding physical processes of devices, ultimately boosting FF and then PCE. Hence, the PM6‐Tz20: Y6‐based OSCs achieved a PCE of up to 17.1% with a significantly enhanced FF of 0.77. Using Ag (220 nm) instead of Al (100 nm) as cathode, the champion PCE was further improved to 17.6%. This work provides a simple and effective molecular design strategy to optimize the active layer morphology of OSCs for improving photovoltaic performance.

A Difluoro‐Monobromo End Group Enables High‐Performance Polymer Acceptor and Efficient All‐Polymer Solar Cells Processable with Green Solvent under Ambient Condition

“…[1][2][3][4][5][6][7] Recently, non-fullerene PSCs based on polymeric donors and small molecular acceptors (SMAs) have achieved remarkable success with the impressive power conversion efficiencies (PCEs) surpassing 17%, owing to the in-depth investigations on the high-performing photovoltaic materials, device optimizations and fundamental aspects such as morphology and charge process. [8][9][10][11][12][13][14][15][16][17] Different from SMA-based PSCs, all-polymer solar cells (all-PSCs), which comprise conjugated polymers as donor and acceptor simultaneously, can provide extra merits of excellent morphological stability, mechanical flexibility, and compatibility with large-scale fabrication like roll-to-roll printing. [18][19][20][21][22][23][24][25][26] Classical improvement in the device performance of the PY-T derivatives as their PCEs still lag far behind relative to those of Y-series small molecule acceptors.…”

Regio‐Regular Polymer Acceptors Enabled by Determined Fluorination on End Groups for All‐Polymer Solar Cells with 15.2 % Efficiency

“…[1][2][3][4][5][6][7] Recently,the bulk-heterojunction (BHJ) PSCs based on polymer donors and small molecule acceptors (SMAs) have progressed rapidly with impressive power conversion efficiencies (PCEs) exceeding 17 %, due to the in-depth investigations on efficient photovoltaic materials,d evice optimization and interfacial engineering. [8][9][10][11][12][13][14][15][16][17] Different from SMA-based PSCs, all-polymer solar cells (all-PSCs), which comprise conjugated polymers as both electron donors and acceptors,provide extra merits of excellent morphological stability,r emarkable mechanical flexibility and suitability for industrial fabrication (e.g.,r oll-to-roll printing). [18][19][20][21][22][23][24][25][26] However,t he major bottleneck that limits the development of all-PSCs is currently the lack of high-performance polymer acceptors with superior photovoltaic properties.…”

A Quinoxaline‐Based D–A Copolymer Donor Achieving 17.62% Efficiency of Organic Solar Cells

“…[ 23 ] In addition, for the purpose of optimizing PM6, ternary copolymerization strategy has also been applied to PM6 to further improve its photovoltaic performance. [ 17,24–26 ] Zhang and co‐workers recently used ternary copolymerization strategy on the basis of PM6 and synthesized the polymers PM1 and PM6‐Tz20 with the introduction of thiazolothiazole and bithiazole units into the polymer main chains, respectively. And, the PCE of the OSCs based on PM1:Y6 and PM6‐Tz20:Y6 both reached 17.6%.…”