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Novel thin film solar cells exhibit unprecedented specific power, which is a key figure of merit for space applications. To get a first indication of their possible degradation in space environments, the OSCAR (‘Optical Sensors based on CARbon materials’) team has built a solar cell performance monitoring system and deployed it on the BEXUS 23 flight. This paper reports the design, testing and performance of said system. Our system performed impeccably over its 4h mission course, maintaining communication and reliably reporting solar cell I-V curves. It forms a guideline for anyone who needs to measure millivolts and microamperes in similar conditions, monitor solar cells on remote locations or wants to follow up on degradation of thin film solar cells in space.

Zonne–energie is ontegensprekelijk één van de belangrijkste en duurzaamste oplossingen voor de globale energie– en klimaatuitdagingen waar onze planeet voor staat. Nieuwe generatie printbare, plooibare en ultra–dunnen zonnecellen kunnen bovendien leiden tot tal van nieuwe toepassingen, gaande van energie–bevoorrading voor draag bare elektronica (smartphones, tablets, …) tot grensverleggende toepassingen voor toekomstige ruimtereizen. Printbare organische en perovskiet–zonnecellen zijn namelijk de wereldkampioenen qua verhouding energie–opbrengst versus gewicht. Voor toekomstige ruimtevaartmissies hebben deze zonnecellen dus de bijzondere voordelen dat ze een ultra–licht gewicht hebben, plooibaar en uitvouwbaar zijn en bovendien ter plaatse (in ruimteschepen of in ruimtestations op bijvoorbeeld de Maan of op Mars) kunnen geprint worden. Door deelname aan het BEXUS–programma (Balloon Experiments for University Students) van de Europese ruimtevaartorganisatie ESA, hebben een team van negen UHasselt–doctoraatstudenten en studenten Fysica (Miguel–Angel Beynaerts, Ilaria Cardinaletti, Rob Cornelissen, Jaroslav Hruby, Steven Nagels, Dieter Schreurs, Jelle Vodnik, Tim Vangerven & Koen Wouters) een wereldrecord gebroken qua gebruik van printbare zonnecellen op grote hoogte. Met het OSCAR–project (Optical Sensors based on CARbon Materials) hebben ze voor het eerste de prestaties van printbare zonnecellen en van een nieuwe magnetische–veldsensor bestudeerd in echte ruimtevaartcondities. Vanuit het lanceerstation Kiruna in Zweden werd een onderzoeksballon in de stratosfeer gebracht — op 32 kilometer hoogte (3x hoogte van vliegtuigtrajecten) — waarbij extreme condities heersen zoals lage luchtdruk, lage temperaturen (tot wel –60 graden Celsius) en een pak meer straling van de zon.

In disordered organic semiconductors, the transfer of a rather localized charge carrier from one site to another triggers a deformation of the molecular structure quantified by the intramolecular relaxation energy. A similar structural relaxation occurs upon population of intermolecular charge-transfer (CT) states formed at organic electron donor (D)-acceptor (A) interfaces. Weak CT absorption bands for D A complexes occur at photon energies below the optical gaps of both the donors and the C-60 acceptor as a result of optical transitions from the neutral ground state to the ionic CT state. In this work, we show that temperature-activated intramolecular vibrations of the ground state play a major role in determining the line shape of such CT absorption bands. This allows us to extract values for the relaxation energy related to the geometry change from neutral to ionic CT complexes. Experimental values for the relaxation energies of 20 D:C-60 CT complexes correlate with values calculated within density functional theory. These results provide an experimental method for determining the polaron relaxation energy in solid-state organic D-A blends and show the importance of a reduced relaxation energy, which we introduce to characterize thermally activated CT processes. This work was supported by the German Federal Ministry for Education and Research (BMBF) through the InnoProfille project "Organische p-i-n Bauelemente 2.2". F.O. would like to thank the German Research Foundation (DFG) for financial support (Grant OR 349/1). This work was partly supported by the DFG within the Cluster of Excellence "Center for Advancing Electronics Dresden." F.P. and D.N. acknowledge funding by the DFG via the SFB 951 "HIOS". T.V. acknowledges the Agency for Innovation by Science and Technology in Flanders (IWT) for funding his Ph.D. The work at Georgia Tech was supported by the Department of the Navy, Office of Naval Research Award No. N00014-14-1-0580 (CAOP MURI) and through a state-sponsored scholarship for graduate students to Y.F. from the China Scholarship Council. We acknowledge the Center for Information Services and High Performance Computing (ZIH) at TU Dresden for computational resources. We thank Prof. Bauerle from the University of Ulm for the supply of DH4T and DH6T and Markus Hummert for P4-Ph4-DIP and BP-Bodipy.

Conjugated polymers and small molecules based on alternating electron-donating (D) and electronaccepting (A) building blocks have led to state-of-the-art organic solar cell materials governing efficiencies beyond 10%. Unfortunately, the connection of D and A building blocks via cross-coupling reactions does not always proceed as planned, which can result in the generation of side products containing D-D or A-A homocoupling motifs. Previous studies have reported a reduced performance in polymer and small molecule solar cells when such defect structures are present. A general consensus on the impact of homocouplings on device performance is, however, still lacking as is a profound understanding of the underlying causes of the device deterioration. For differentiating the combined effect of molecular weight and homocouplings in polymer solar cells, a systematic study on a small molecule system (DTS(FBBTh2)2) is presented. The impact of homocouplings on nanomorphology, thermal, and electro-optical properties is investigated. It is demonstrated that small quantities of homocouplings (