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In the quest for indium-tin oxide (ITO)-free photovoltaics and for building integrated as well as automobile roof applications, novel transparent electrodes for both front and back electrodes are required. Here we report the fabrication and integration of submicrometer transparent silver (Ag) and gold (Au) metal network electrodes, which are invisible to the naked eye, in organic photovoltaic devices. We exploit the idea of using the spontaneous cracking of a polymer layer as template to prepare the metal network. The main challenge is to apply the cracked template approach on top of soluble organic layers and to lift off the template without damaging the photoactive layer. We demonstrate that Ag or Au back electrodes can be fabricated maintaining a transmittance of 80 % for the whole visible range. These electrodes exhibit ultralow haze of approximately 5 % and an excellent figure of merit value. Moreover, the ITO-free semitransparent polymer solar cell incorporating the Ag/Ag network electrodes exhibits 57 % transmittance above 650 nm. [ABSTRACT FROM AUTHOR]

Nanostructured metal mesh structures demonstrating excellent conductivity and high transparency are one of the promising transparent conducting electrode (TCE) alternatives for indium tin oxide (ITO). Often, these metal nanostructures are to be employed as hybrids along with a conducting filler layer to collect charge carriers from the network voids and to minimize current and voltage losses. The influence of filler layers on dictating the extent of such ohmic loss is complex. Here, we used a general numerical model to correlate the sheet resistance of the filler, lateral charge transport distance in network voids, metal mesh line width and ohmic losses in optoelectronic devices. To verify this correlation, we prepared gold or copper network electrodes with different line widths and different filler layers, and applied them as TCEs in perovskite solar cells. We show that the photovoltaic parameters scale with the hybrid metal network TCE properties and an Au-network or Cu-network with aluminum-doped zinc oxide (AZO) filler can replace ITO very well, validating our theoretical predictions. Thus, the proposed model could be employed to select an appropriate filler layer for a specific metal mesh electrode geometry and dimensions to overcome the possible ohmic losses in optoelectronic devices. [ABSTRACT FROM AUTHOR]