Acene ring size optimization in fused lactam polymers enabling high n-type organic thermoelectric performance by Chen, H, Moser, M, Wang, S, Jellett, C, Thorley, K, Harrison, GT, Jiao, X, Xiao, M, Purushothaman, B, Alsufyani, M, Bristow, H, De Wolf, S, Gasparini, N, Wadsworth, A, McNeill, CR, Sirringhaus, H, Fabiano, S, McCulloch, I