{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,2]],"date-time":"2026-05-02T09:27:57Z","timestamp":1777714077153,"version":"3.51.4"},"reference-count":127,"publisher":"MDPI AG","issue":"12","license":[{"start":{"date-parts":[[2018,12,16]],"date-time":"2018-12-16T00:00:00Z","timestamp":1544918400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Materials"],"abstract":"<jats:p>Organic photovoltaic (OPV) devices, made with semiconducting polymers, have recently attained a power conversion efficiency (PCE) over 14% in single junction cells and over 17% in tandem cells. These high performances, together with the suitability of the technology to inexpensive large-scale manufacture, over lightweight and flexible plastic substrates using roll-to-roll (R2R) processing, place the technology amongst the most promising for future harvesting of solar energy. Although OPVs using non-fullerene acceptors have recently outperformed their fullerene-based counterparts, the research in the development of new fullerenes and in the improvement of the bulk-heterojunction (BHJ) morphology and device efficiency of polymer:fullerene solar cells remains very active. In this review article, the most relevant research works performed over the last 3 years, that is, since the year 2016 onwards, in the field of fullerene-based polymer solar cells based on the copolymers PTB7, PTB7-Th (also known as PBDTTT-EFT) and PffBT4T-2OD, are presented and discussed. This review is primarily focused on studies that involve the improvement of the BHJ morphology, efficiency and stability of small active area devices (typically &lt; 15 mm2), through the use of different processing strategies such as the use of different fullerene acceptors, different processing solvents and additives and different thermal treatments.<\/jats:p>","DOI":"10.3390\/ma11122560","type":"journal-article","created":{"date-parts":[[2018,12,18]],"date-time":"2018-12-18T02:15:59Z","timestamp":1545099359000},"page":"2560","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":73,"title":["Recent Developments in the Optimization of the Bulk Heterojunction Morphology of Polymer: Fullerene Solar Cells"],"prefix":"10.3390","volume":"11","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-7063-8462","authenticated-orcid":false,"given":"Hugo","family":"Gaspar","sequence":"first","affiliation":[{"name":"IPC\/i3N\u2014Institute for Polymers and Composites, University of Minho, Campus de Azur\u00e9m, 4800-058 Guimar\u00e3es, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3685-9736","authenticated-orcid":false,"given":"Fl\u00e1vio","family":"Figueira","sequence":"additional","affiliation":[{"name":"QOPNA, Departament of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5482-0715","authenticated-orcid":false,"given":"Luiz","family":"Pereira","sequence":"additional","affiliation":[{"name":"Department of Physics and i3N\u2014Institute for Nanostructures, Nanomodelling and Nanofabrication, University of Aveiro, 3810-193 Aveiro, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2472-3265","authenticated-orcid":false,"given":"Ad\u00e9lio","family":"Mendes","sequence":"additional","affiliation":[{"name":"LEPABE, Department of Chemical Engineering, University of Porto, 4200-465 Porto, Portugal"}]},{"given":"J\u00falio C.","family":"Viana","sequence":"additional","affiliation":[{"name":"IPC\/i3N\u2014Institute for Polymers and Composites, University of Minho, Campus de Azur\u00e9m, 4800-058 Guimar\u00e3es, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7392-4915","authenticated-orcid":false,"given":"Gabriel","family":"Bernardo","sequence":"additional","affiliation":[{"name":"LEPABE, Department of Chemical Engineering, University of Porto, 4200-465 Porto, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2018,12,16]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"36","DOI":"10.1016\/S1369-7021(12)70019-6","article-title":"Roll-to-roll fabrication of polymer solar cells","volume":"15","author":"Angmo","year":"2012","journal-title":"Mater. 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