Progress in Materials, Solution Processes, and Long‐Term Stability for Large‐Area Organic Photovoltaics

Abstract

processing at low cost compared with their inorganic counterparts. The first breakthrough in OPV technology was achieved by realizing BHJ active layers with nanoscale bicontinuous network structures of electron donor (D) and acceptor (A) materials; this structure enables efficient exciton separation at the D-A interface. [1] The development of push-pull-type donor polymers has effectively extended the light absorption range of OPVs into the near-infrared (NIR) region, which has ultimately led to substantial improvements in power conversion efficiency (PCE) to greater than 10%. In particular, highly crystalline donor polymers such as PffBT4T-2OD substantially improved charge-transport properties, enabling OPV devices with a BHJ film thickness greater than 200 nm to operate. [2] Historically, fullerene derivatives have been dominantly used as acceptors in OPVs because of their excellent electron-accepting and transporting properties and because they can be prepared with a morphology optimized for efficient charge-carrier generation and transport. [3,4] However, despite such promising characteristics, OPVs based on fullerene derivatives have drawbacks of limited light-absorption properties, poor energylevel tunability, and poor morphological and/or photochemical stability. [5,6] Over the past several years, tremendous efforts have been directed toward the development of nonfullerenebased OPVs to overcome these limitations. The advantages of nonfullerene acceptors over fullerenes include easily tunable energy levels, which enables OPVs to achieve substantially higher open-circuit voltages (V OC s) than conventional fullerenebased devices. [7] In addition, nonfullerene acceptors enable better light absorption properties and therefore generate higher photocurrents than fullerene derivatives. [8] Furthermore, nonfullerene acceptors with appropriate molecular tailoring can provide chemically stable photoactive materials, potentially enhancing long-term device stability. [5] Recent breakthroughs realized through the development of small molecular nonfullerene acceptors have resulted in remarkable enhancements in the PCEs of single-junction OPVs to greater than 17%, which demonstrates the potential for the large-scale manufacture of OPVs. [9] When translating photovoltaic technology from laboratory to commercial products, low cost, high PCE, and high Organic solar cells based on bulk heterojunctions (BHJs) are attractive energy-conversion devices that can generate electricity from absorbed sunlight by dissociating excitons and collecting charge carriers. Recent breakthroughs attained by development of nonfullerene acceptors result in significant enhancement in power conversion efficiency (PCEs) exceeding 17%. However, most of researches have focused on pursuing high efficiency of small-area (<1 cm 2) unit cells fabricated usually with spin coating. For practical application of organic photovoltaics (OPVs) from lab-scale unit cells to industrial products, it is essential to develop efficient technologies that can extend act...

Nonhalogenated‐Solvent‐Processed High‐Performance All‐Polymer Solar Cell with Efficiency over 14%

“…[ 9–12 ] Recently, the power conversion efficiency (PCE) of all‐PSCs has been significantly boosted to over 15%, primarily due to the substantial efforts devoted to active‐layer material design, [ 13–17 ] device engineering, and bulk heterojunction morphology control, [ 18,19 ] demonstrating a great potential toward future practical application. [ 20,21 ]…”

Up-scalable emerging energy conversion technologies enabled by 2D materials: from miniature power harvesters towards grid-connected energy systems

“…9,10,325 It is noteworthy to mention that thin-film, lab-scale PePV and OPV with high efficiencies have been already obtained leading to record PCE values of 25.2% and 418%, respectively. [326][327][328][329][330][331] Intensive developments are continually being made for reducing the PCE gap between small and large-area modules, while achieving a high throughput, high stability, and minimum batch-to-batch variation, at lowest possible manufacturing cost. The atomically thin bodies and high flexibility of GRM make them the obvious choice to be integrated into PePV or OPV, serving as a complementary approach to Si for future-generation PV technology.…”

Progress in Upscaling Organic Photovoltaic Devices

“…[43,[50][51][52][53] Other challenges concerns the development of new molecularly engineered donor and acceptor materials that can exhibit a high efficiency when formed into thick active layers (desirable for upscaling). [42,43,54,55] These challenges have been previously rev iewed, [42,43,50,54,56] including some very recent reviews, [42,43,50,54] and will not be the subject of specific attention here.…”