The high performance of OSCs with the optimal thickness of 100 nm is strongly related to the nanoscale formation of BHJ during and after the processing. However, upscaling of such devices from the laboratory to industry demands thicker photoactive layer as is needed to gain robust printing processes. However this may lead to serious losses in the efficiency in NFA based solar cells[1,2] due to enhanced recombination induced by longer transport paths towards the electrodes in combination with reduced electric fields inside the device. Nevertheless, under low light conditions, thick photoactive blends exhibit less space charge effects, leading to less recombination of the charge carriers[3] which is simply connected to less photon flux produced by low intensity indoor illumination. Furthermore, transfer to less toxic processing is an essential requirement for the scalable deposition techniques such as roll-to-roll or other printing techniques usually combined with photoactive layers with more than 200 nm thickness[4,5].

 In this work, the non-halogenated ink formulation was applied to doctor blade in air PM6:ITIC-4F-based blends. In order to further approach the industrial relevant processing conditions, another promising wide band-gap polymer PTQ-10[6] was exploited due to the low cost, solubility in non-halogenated solvents[7], high efficiency and thick layer potential processing of this material[6,8].  Identical ink formulations using OX:tetralin mixture were applied to PTQ-10:ITIC-4F blends allowing to compare the performance of corresponding solar cells using thick blends as a function of donor polymer as well as thermal post-treatment. The photovoltaic properties of the solar cells were studied under two light sources, i.e. simulated AM 1.5G and indoor light at 200 and 1000 Lux, to learn more about recombination losses in OSC using thick blends. Under optimal processing conditions PM6:ITIC-4F blends produce OSCs with a PCE of 9.3 % for 300 nm thick layer under 1 sun illumination  and 14.78% under low light conditions (200 Lux), respectively, while the use of thicker blend layers lead to lower efficiencies. In contrast, OSCs based on PTQ-10:ITIC-4F blends  showed highest PCE for  500 nm thick layer with a PCE of 11.3 % under 1 sun illumination and 15.71% under indoor light at 200 Lux. The difference in performance for optimized thick layers between the two blend systems could be addressed to the different behavior of PM6 and PTQ-10 phase separation when blended with ITIC-4F, together with the difference of the surface composition of the films after drying.