After a brief review of the recent evolvement of organic-silicon heterojunction solar cells, we present here our latest measurements of the saturation current densities (J(0)) and contact resistances (R-C) of crystalline silicon (c-Si)/poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) junctions. We determine the J(0) values by means of contactless carrier lifetime measurements and the RC values by comparing sheet resistance measurements with numerical device simulations of the corresponding test structure. Application of an adopted PEDOT: PSS blend and an optimized silicon surface treatment results in a minimal J(0) value of 46 fA/cm(2), limiting the solar cell open-circuit voltage to V-oc_limit=708 mV, and a minimal RC value of 100 m Omega cm(2). Our optimized silicon surface pre-treatment in combination with the adapted PEDOT: PSS blend are successfully implemented into a cell process with the PEDOT: PSS layer located at the rear surface (the so-called 'BackPEDOT concept'). Record-high efficiencies of 18.3% and of 20.6% are achieved on p-type silicon and on p-type silicon wafers, respectively. Finally, we compare the internal quantum efficiency of our champion BackPEDOT solar cell with that of a state-of-the-art Al2O3/SiNx-passivated PERC solar cell. (C) 2015 The Authors. Published by Elsevier Ltd.

A non-aqueous Poly(3,4-ethylenedioxythiophene): poly(styrenesulfonic acid) (PEDOT:PSS) dispersion was developed to enable the accommodation of non-polar additives. This additional functionalisation targets selected interface characteristics and results in an improved adhesion of PEDOT:PSS on the photo-active layer. Such mechanical robustness is paramount in inverted organic photovoltaic cells contributing to improved long-term stability.

This work attempts to reveal the comparability issues related to outdoor testing procedures of organic photovoltaic (OPV) modules via studies of inter-laboratory long-term outdoor measurements of roll-to-roll coated flexible OPV modules (P3HT:PCBM, inverted architecture) in different geographic locations from both Southern and Northern hemispheres. The interpretation of the module degradation via sub-cell analyses is presented and the poor reproducibility of the module performance linked to the barrier properties of the encapsulation around the device terminals is addressed. We demonstrate that the modules' t80 lifetime may vary between a few hundred to over 10,000h depending on how well the device terminals are sealed. We additionally demonstrate up to 17 months of stable performance for sub-cells within the modules. Furthermore, the effects of different geographical locations, weather conditions and measurement setups on the comparability of test results are analyzed. A strong link between the device temperature and performance is revealed, which is ascribed to the reaction of PEDOT:PSS layer with water. The estimation of the true performance of the modules by accommodation of variations in testing conditions is performed. Based on the results a set of recommendations from the ISOS-O guiding protocols are highlighted, which can help remove the factors that affect the comparability of the test results.

We report on bulk structures of a family of quaterthiophene (4T) derivatives with linear and branched end groups such as alpha,alpha'-dihexylquaterthiophene (Hex-4T-Hex), alpha,alpha'-didecyl-quaterthiophene (Dec-4T-Dec) and alpha,alpha'-bis(2-ethylhexyl)quaterthiophene (EH-4T-EH), tetramethyldisiloxane-based dimers D2-Und-4T-EH and D2-Und-4T-Hex, and carbosilane-siloxane-based tetramers D4-Und-4T-EH and D4-Und-4T-Hex. The dimers and tetramers contain undecylenic (Und) spacers between the disiloxane and 4T- units of the molecule. The impact of the molecular architecture on the bulk structure at different temperatures is addressed with X-ray diffraction and differential scanning calorimetry. For all of the studied quaterthiophene-containing organosilicon multipods the formation of 4T-crystal sublattice is observed. The alkyl periphery plays an important role in the molecular packing and thermal stability of the ordered phase. They can stabilize or destabilize the crystal phase, depending on their length and architecture. The quaterthiophenes with 2-ethylhexyl end groups adopt a zig-zag conformation in the crystalline state at room temperature. This change of conformation leads to a significant decrease of the polymorphic transition and isotropization temperatures. The efficiency of 4T packing in the sublattice is estimated from the molecular cross-section (S) in the plane normal to the molecular axis. Correlations between S and field-effect charge carrier mobility are established.

Indium tin oxide (ITO) is widely used as electrode in the display industry. This chapter focuses on conductive polymers as ITO replacement. It describes the properties of intrinsically conductive polymers in general and those of the poly(3,4-ethylene dioxythiophene) (PEDOT), the most advanced intrinsically conductive polymer (ICP) in terms of conductivity and transparency, in particular. The synthesis of PEDOT is described and its conductivity, transmission, and refractive index are compared to that of ITO. Finally, first examples of PEDOT as ITO replacement are given.

A new star-shaped D–π–A molecule, tris{4-[5′′-(1,1-dicyanobut-1-en-2-yl)-2,2′-bithiophen-5-yl]phenyl}amine N(Ph-2T-DCN-Et)3, with high efficiency potential for photovoltaic applications was synthesized. As compared to its analogue S(TPA-bT-DCN), it showed stronger absorption in the region of 350–450nm and a lower lying highest occupied molecular energy level (HOMO). Solution-processed organic solar cells (OSCs) based on a blend of N(Ph-2T-DCN-Et)3 and PC70BM resulted in a high PCE of 3.1% without any post-treatment. The PCE of N(Ph-2T-DCN-Et)3 based solar cells was further improved to 3.6% under simulated AM 1.5 by addition of a new additive 4-bromoanisole (BrAni).

A large number of flexible polymer solar modules comprising 16 serially connected individual cells was prepared at the experimental workshop at Risø DTU. The photoactive layer was prepared from several varieties of P3HT (Merck, Plextronics, BASF and Risø DTU) and two varieties of ZnO (nanoparticulate, thin film) were employed as electron transport layers. The devices were all tested at Risø DTU and the functional devices were subjected to an inter-laboratory study involving the performance and the stability of modules over time in the dark, under light soaking and outdoor conditions. 24 laboratories from 10 countries and across four different continents were involved in the studies. The reported results allowed for analysis of the variability between different groups in performing lifetime studies as well as performing a comparison of different testing procedures. These studies constitute the first steps toward establishing standard procedures for an OPV lifetime characterization.