High efficiency arrays of polymer solar cells fabricated by spray‐coating in air

Abstract

We present bulk heterojunction organic solar cells fabricated by spray‐casting both the PEDOT:PSS hole‐transport layer (HTL) and active PBDTTT‐EFT:PC71BM layers in air. Devices were fabricated in a (6 × 6) array across a large‐area substrate (25 cm2) with each pixel having an active area of 6.45 mm2. We show that the film uniformity and operational homogeneity of the devices are excellent. The champion device with spray cast active layer on spin cast PEDOT:PSS had an power conversion efficiency (PCE) of 8.75%, and the best device with spray cast active layer and PEDOT:PSS had a PCE of 8.06%. The impacts of air and light exposure of the active layer on device performance are investigated and found to be detrimental. Copyright © 2015 John Wiley & Sons, Ltd.

Solution modification of PEDOT:PSS inks for ultrasonic spray coating

“…Indeed, we have previously deposited PEDOT:PSS by spray coating [19,20] Critically, we also add 0.015 mg ml -1 PEG that as we show below, controls thin-film viscosity and helps to improve film uniformity. This allows us to increase the processing time window significantly and to improve film uniformity across the substrate (characteristics important in any practical manufacture process).…”

“…The oscillations of the spray-head break the liquid into a very fine mist that is then directed to a surface via a focussed jet of compressed gas. This technique has been used by us [19][20][21][22] and others [23][24][25][26] to deposit highquality, uniform polymeric films for optoelectronic devices without the use of surfactants.…”

“…To optimise film quality using this solvent mixture, we have found that it is critical to rapidly evaporate any remaining EG present within the film using a second high temperature annealing stage. [19,20] In parts (d) and (h) we show a film in which a small concentration of PEG has been added to a solution containing IPA and EG. The addition of the very high molecular weight PEG is found to increase the viscosity of the deposited solution resulting from a physical entanglement between the polymer chains.…”

Fabricating high performance conventional and inverted polymer solar cells by spray coating in air

“…In contrast, spray coating has been used in the fabrication of OPVs and is compatible with large area processing over flexible substrates. [11][12][13][14][15] Notably, most work on the development of spray cast…”

“…[16] More recent work has however explored spray-cast blends of amorphous donor-acceptor co-polymers with fullerene-derivative electron acceptors, with improved device performance demonstrated. [11,13,17,18] Spray-coating has also been used to deposit the various charge transporting layers used in OPV devices. [19] In single junction OPV device based on a conventional architecture, the active layer is deposited onto a hole-transporting layer.…”