Round‐Robin Studies as a Method for Testing and Validating High‐Efficiency ITO‐Free Polymer Solar Cells Based on Roll‐to‐Roll‐Coated Highly Conductive and Transparent Flexible Substrates

Abstract

COMMUNICATION 1091 wileyonlinelibrary.com www.MaterialsViews.com www.advenergymat.dePhotovoltaic cells [ 1 ] based on organic and polymer materials (OPVs) are celebrated as being a possible solution to the energy needs of the future, [ 1b ] and, with record effi ciencies having breached the 10% milestone accompanied by emerging involvement from the materials industry, expectations are rapidly approaching reality. [ 1c ] However, in order to move OPVs beyond the individual laboratory and into a generally applied setting, scientists need to limit the gap between carefully prepared hero devices and the large-scale manufacture of thousands of devices. We propose that this is done by urgently attending to the challenges of scalability and reproducibility. In this communication, we demonstrate an approach using round-robin testing as a method to validate effi ciency measurements of OPVs based on semitransparent electrodes on fl exible substrates, with and without indium tin oxide (ITO). ITO-free substrates were rollto-roll coated under ambient conditions and were truly scalable. Our results demonstrate inherent uncertainties in the device-effi ciency data, with variations in the carefully measured effi ciency data for the same device between highly qualifi ed laboratories as high as 25%, depending on the substrate and its active area.Thus the concrete needs of society impose a broadening of the scientifi c perspective, but also a requirement for the validation and verifi cation of reports. The view should thus be that it is no longer enough to report very high effi ciency unless several independent laboratories report it. In a few instances, laboratories have obtained certifi ed effi ciency data for record devices, but, in practical terms, this effi cient solution represents a bottleneck, as very few laboratories have the capacity to offer certifi cation, and it would not be possible to certify all efficiency reports with the currently available laboratories. Instead, concerns of the validity of effi ciency data and reproducibility should be tackled by employing interlaboratory studies and round robins, in an effort to gain a consensus and gradually approach standardization. [2][3][4] Regarding the important issue of scalability, the average effi ciency of many devices prepared by large-scale methods is unlikely to rival current record effi ciencies. It has been argued that it is no longer enough to present high effi ciencies, focusing on the decimals of the reported numbers, without seriously addressing which processes and which materials can reasonably be included when fabricating polymer solar cells on what will eventually be a GW p per day scale. To do this, considerations of both the economic and environmental impact should be made. [ 1b ] In this regard, a systematic approach to such considerations as, for example, offered by life-cycle assessments is very important at this point. [ 1 , 5-7 ] Such studies reveal the favorite transparent electrode material, ITO, as being the most-critical bottleneck for state-...

Roll‐to‐Roll fabrication of large area functional organic materials

“…[12][13][14] Larsen- Olsen et al showed that the use of high-conductive PEDOT:PSS with or without a preprocessed silver collecting grid can be used as a substitute for ITO in inverted structure devices and modules with good results. 12,14 By appliance of a short pulse at high negative bias to the solar cell, it is possible to electrochemically ''switch'' (reduce) a thin layer of the top PEDOT causing a permanent conductivity change rendering it a rectifying junction.…”

“…[12][13][14] Larsen- Olsen et al showed that the use of high-conductive PEDOT:PSS with or without a preprocessed silver collecting grid can be used as a substitute for ITO in inverted structure devices and modules with good results. 12,14 By appliance of a short pulse at high negative bias to the solar cell, it is possible to electrochemically ''switch'' (reduce) a thin layer of the top PEDOT causing a permanent conductivity change rendering it a rectifying junction. Further studies on the use of different types of front grids in the same process were carried out by Yu et al showing that thermally embedded silver grids and flexo printed silver grids result in solar cells with similar efficiencies (slightly better for the embedded grid), whereas solar modules with inkjet printed silver front grid performed poorer, which was ascribed to the lower conductivity of the grid.…”

Layer‐by‐Layer Solution‐Processed Low‐Bandgap Polymer‐PC61BM Solar Cells with High Efficiency

“…In particular, organic solar cells (OSCs) have been the focus of research in the past decade due to some advantages such as simple preparation with ambient temperature and pressure, low cost, light weight and fl exibility. [1][2][3][4][5][6] In recent years, numerous literatures focused on design and synthesis of donor materials, [7][8][9][10][11][12][13][14] fullerene derivative or non-fullerene acceptor materials, [15][16][17][18] optimization of device performance [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] and roll-to-roll coating techniques; [36][37][38] these efforts have promoted power conversion effi ciency (PCE) of OSCs exceeding 9%. [39][40][41][42][43] Lateral and vertical phase separation is very important to OSCs, [44][45][46]…”

Controlling donor crystallinity and phase separation in bulk heterojunction solar cells by the introduction of orthogonal solvent additives

“…Organic electronics remains an active area of research and development, mainly due to the potential low-cost production [1], [2], [3], flexibility [4], [5] or semitransparency [6], [7]. Firstly, applications in modern science, e.g.…”