Tregnago, G; Wykes, M; Paterno, GM; Beljonne, D; Cacialli, F; (2015) Low-Temperature Photoluminescence Spectroscopy of Solvent-Free PCBM Single-Crystals. Journal of Physical Chemistry C , 119 (21) pp. 11846-11851. 10.1021/acs.jpcc.5b02345.