Achieving 6.7% Efficiency in P3HT/Indene-C70 Bisadduct Solar Cells through the Control of Vertical Volume Fraction Distribution and Optimized Regio-Isomer Ratios by Kutsarov, D, Rašović, I, Zachariadis, A, Laskarakis, A, Lebedeva, M, Porfyrakis, K, Mills, C, Beliatis, M, Fisher, B, Bruchlos, K, Ludwigs, S, Logothetidis, S, Silva, S