Eco-Friendly Push-Coated Polymer Solar Cells with No Active Material Wastes Yield Power Conversion Efficiencies over 5.5%

Abstract

Push-coating is a simple process that can be employed for extremely low-cost polymer electronic device production. Here, we demonstrate its application to the fabrication of poly­(2,7-carbazole-alt-dithienylbenzothiadiazole) (PCDTBT):[6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) active layers processed in air, yielding similar photovoltaic performances as thermally annealed spin-coated thin films when used in inverted polymer solar cells (PSCs). During push-coating, the polydimethylsiloxane layer temporarily traps the deposition solvent, resulting in simultaneous film formation and solvent annealing effect. This removes the necessity for a postdeposition thermal annealing step which is required for spin-coated PSCs to produce high photovoltaic performances. Optimized PSC active layers are produced with a push-coating time of 5 min at room temperature with 20 times less hazardous solvent and 40 times less active material than spin-coating. Annealed spin-coated active layers and active layers push-coated for 5 min both produce average power conversion efficiencies (PCEs) of 5.77%, while those push-coated for a shorter time of 1 min yield a slightly lower value of 5.59%. We demonstrate that, despite differences in their donor:acceptor vertical concentration gradients, unencapsulated PCDTBT:PC71BM active layers push-coated for 1 min produce PSCs with similar operational stability and upscaling capacity as thermally annealed spin-coated ones. As fast device fabrication can be achieved with short-time push-coating, we further demonstrate the potential of this deposition technique by manufacturing push-coated PSC-based semitransparent photovoltaic devices with a PCE of 4.23%, relatively neutral colors and an average visible transparency of 40.2%. Our work thus confirms that push-coating is not limited to the widely employed poly­(3-hexylthiophene-2,5-diyl) but can also be used with low band gap copolymers and opens the path to low-cost and eco-friendly, yet efficient and stable PSCs.

Ultrafast spectroscopy on water-processable PCBM: rod–coil block copolymer nanoparticles

“…Note that several strategies are currently being investigated to manufacture OSCs using environment-friendly solvents or to minimize the volume of solvent employed. 4,24 From a toxicity point-of-view, water is the ideal choice as OSC processing solvent. Consequently, the concept of water-dispersed conjugated polymer nanoparticle inks have gained considerable attention for the green processing of OSC active layers.…”

Fast Wetting of a Fullerene Capping Layer Improves the Efficiency and Scalability of Perovskite Solar Cells

“…It is well known that the drop-casting method is more material-saving compared with the conventional spin-coating method. During the spin-coating procedure most of the material (>90%) is wasted because of the ejection of the solution, whereas almost all the material will be used to form the film when an appropriate dosage solution is used during the drop-casting procedure. , The fast wetting of the PCBM–0.15IPA:CB solution on the perovskite film encouraged us to fabricate the PCBM capping layer via a facile drop-casting method. Depending on the size of the substrate, an appropriate amount of the solution was dropped onto the surface of the perovskite film (about 2 μL for a 1.5 × 1.5 cm 2 substrate).…”

Controlling the concentration gradient in sequentially deposited bilayer organic solar cells via rubbing and annealing

“…Furthermore, before suggesting rubbing as a universal strategy to improve the performances of BL OSCs, the versatility of the process with respect to the employed materials should be elucidated. Unlike the highly crystalline P3HT, PCDTBT is an amorphous material that generally yields higher PV performances at processing temperatures below 100 C. [41][42][43] However, previous attempts to produce ADP PCDTBT-based BL OSCs resulted in fairly poor PV performances. 44 In fact, Seok et al proposed to use solvent additives to promote the formation of adequate vertical concentration gradients in PCDTBT/PCBM BLs.…”