Fully Spray-Coated Organic Photovoltaic Cells with Green Solvents: Study of Interfaces and Scale-Up
Giuseppina Polino a, Luca La Notte a, Simone Dell'Elce b, Andrea Liscio b c, Giorgio Cardone d, Babak Taheri a, Aldo Di Carlo a, Andrea Reale a, Francesca Brunetti a
a CHOSE- Centre for Hybrid and Organic Solar Energy, University of Rome “Tor Vergata”, Electronic Engineering Department, Via Giacomo Peroni 400, Rome, 131, Italy
b Istituto per la Sintesi e la Fotoreattivita` CNR, via Gobetti 101, Bologna, 40120, Italy
c Istituto dei sistemi complessi CNR
d PPG Italy Business Support SRL
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV19)
Roma, Italy, 2019 May 12th - 15th
Organizers: Prashant Kamat, Filippo De Angelis and Aldo Di Carlo
Oral, Giuseppina Polino, presentation 072
DOI: https://doi.org/10.29363/nanoge.hopv.2019.072
Publication date: 11th February 2019

The introduction of low-band-gap polymer donors in organic bulk heterojunction solar cells allowed to achieve high power conversion efficiency (PCE) [1]. Such optimal performance are strongly correlated to the use of spin coating as technique to ensure reproducible and homogeneous films and chlorinated solvents that help the suitable nanoscale morphology. But this procedure is not industry compatible since spin coating does not allow large scale production and chlorinated solvents are poorly tolerated in workplaces since they are harmful towards environment and human health [2,3]. For this reason, we realized high-performing inverted polymer solar cells by depositing all the layers through a scalable technique as spray coating [4] by using green solvents. We investigated the morphology at the interface between photoactive layer (PAL) deposited through a non-chlorinated solvent (ortho-xylene) and hole and electron transport layers processed from alcohol based solvents, via atomic force microscopy (AFM). In particular, we analyzed the interface between PAL and an electron transport layer (ETL) fabricated using zinc oxide nanoparticles coated with polyethylenimine ethoxylated (PEIE) [5]. Then, we studied the interface between PAL and three different combination of  hole transport layer (HTL)/anode: i) a mixture of two commercial poly(3,4- ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) formulations (CPP:PH1000), ii)  an anhydrous PEDOT:PSS (A-PEDOT) dispersion developed in our laboratory, iii) a double layer composed of vanadium (V) oxide (V2O5) and PH1000 electrode. Finally, we evaluated the electrical performance of small area devices (10 mm2) realized using the three typologies of HTL/Anode interfaces, obtaining comparable results in terms of PCE in the case of V2O5/PH1000 (3.25%) and anhydrous PEDOT:PSS (3.6%) when the devices were illuminated from ITO side. By illuminating from the PEDOT side, the PCE decreased of 26% in the case of V2O5/PH1000 and was halved in the case of A-PEDOT. Therefore, we decide to fabricate and electrically characterize organic photovoltaic modules (active area: 13 cm2) with ITO/ZnO-PEIE/PTB7:PC70BM/V2O5/PH1000 structure, by demonstrating the successful application of spray coating for scale-up of Organic Photovoltaics.

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